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1<h3>BKG Ntrip Client (BNC) Version 1.7</h3>
2
3<p>
4The BKG Ntrip Client (BNC) is a program for simultaneously retrieving, decoding and converting real-time GNSS data streams from NTRIP broadcasters like <u>http://www.euref-ip.net/home</u> or <u>http://www.igs-ip.net/home</u>.
5</p>
6
7<p>
8BNC has been developed for the Federal Agency for Cartography and Geodesy (BKG) within the framework of EUREF's Real-time GNSS Project (EUREF-IP, IP for Internet Protocol) and the Real-Time IGS Pilot Project (RTIGS).
9</p>
10
11<p>
12BNC has been written under GNU General Public License (GPL). Binaries for BNC are available for Windows, 32-bit Linux, 64-bit Linux (compiled using option -m32), Solaris, and Mac systems. We used the MinGW Version 5.3.1 compiler to create the Windows binary. It is likely that BNC can be compiled on other systems where a GNU compiler and Qt Version 4.4.3 are installed.
13</p>
14
15<p>
16Please ensure that you have installed the latest version of BNC available from <u>http://igs.bkg.bund.de/index_ntrip_down.htm</u>. We are continuously working on the program and would appreciate if you could send any comments, suggestions, or bug reports to [euref-ip@bkg.bund.de] or [igs-ip@bkg.bund.de].
17</p>
18
19<h3>Contents</h3>
20<p>
21<h4>
22<a href=#purpose>1. Purpose</a><br>
23<a href=#resources>2. Modes & Resources</a><br>
24<a href=#options>3. Options</a><br>
25<a href=#limits>4. Limitations</a><br>
26<a href=#authors>5. Authors</a><br>
27<a href=#annex>8. Annex</a><br>
28</h4>
29</p>
30
31<p><a name="purpose"><h3>1. Purpose</h3></p>
32
33<p> The purpose of BNC is to
34
35<ul>
36<li>retrieve real-time GNSS data streams available through NTRIP transport protocol,</li>
37<li>generate high-rate RINEX Observation and Navigation files to support near real-time GNSS post-processing applications, and/or</li>
38<li>generate ephemeris and synchronized or unsynchronized observations epoch by epoch through an IP port to support real-time GNSS network engines, and/or</li>
39<li>generate clock and orbit corrections to broadcast ephemeris through an IP port to support real-time Precise Point Positioning on GNSS rovers, and/or</li>
40<li>generate synchronized clock and orbit corrections to broadcast ephemeris epoch by epoch through an IP port to support the combination of such streams as coming simultaneously from various correction providers, and/or</li>
41<li>monitor the performance of a network of real-time GNSS data streams to generate advisory notes, and/or</li>
42<li>scan RTCM streams for incoming antenna information as well as message types and their repetition rates, and/or</li>
43<li>feed a stream into a GNSS rover via serial communication link.</li>
44</ul>
45</p>
46<p>
47BNC supports the following GNSS data formats:
48</p>
49<p>
50<ul>
51<li>RTCM Version 2.x containing message types 18 and 19 or 20 and 21 together with 3 and 22 (GPS and GLONASS), </li>
52<li>RTCM Version 3.x containing message types 1002 (GPS, SBAS) or 1004 (GPS), 1010 or 1012 (GLONASS), 1019 or 1020 (broadcast ephemeris), 4056 and 4057 (premature messages for combined orbit and clock corrections to GPS and GLONASS broadcast ephemeris)</li>
53<li>RTIGS containing GPS record types 200 (observations) and 300 (ephemeris).</li>
54</ul>
55BNC allows to by-pass its decoding and conversion algorithms, leave whatever is received untouched and save it in files.
56</p>
57<p><a name="resources"><h3>2. Modes & Resources</h3></p>
58<p>
59Although BNC is a real-time tool to be operated in online mode, it can be run offline for post processing of data made availabe from a file. Furthermore, apart from its regular window mode, BNC can be run as a batch/background job in a 'no window' mode using processing options from previously saved configuration.
60</p>
61<p>
62Unless in offline mode, BNC
63</p>
64<ul>
65<li>requires access to the Internet with a minimum of about 2 to 6 kbits/sec per stream depending on the stream format and the number of visible satellites. You need to make sure that the connection can sustain the required bandwidth.</li>
66<li>requires the clock of the host computer to be properly synchronized.</li>
67<li>has the capacity to retrieve hundreds of GNSS data streams simultaneously. Please be aware that such usage may incur a heavy load on the NTRIP broadcaster side depending on the number of streams requested. We recommend limiting the number of streams where possible to avoid unnecessary workload.</li>
68</ul>
69</p>
70
71<p><a name="options"><h3>3. Options</h3></p>
72<p>
73The usual handling of BNC is that you first select a number of streams from NTRIP broadcasters ('Add Streams'). Any stream configured to BNC shows up on the 'Streams' canvas in the middle of BNC's main window. You then go through BNC's various tabs to select a combination of processing options before you start the program ('Start'). Records of BNC's activities are shown in the 'Logs' canvas on the bottom of the main window.
74</p>
75<p>
76As a default, configuration files for running BNC on Unix/Linux/Mac systems are saved in directory '${HOME}/.config/BKG'. On Windows systems, they are typically saved in directory 'C:/Documents and Settings/Username/.config/BKG'. The default configuration file name is 'BNC.ini'.</p>
77<p>
78The default file name 'BNC.ini' can be changed and the file contents can easily be edited. On graphical user interfaces it is possible to Drag & Drop a configuration file icon to start BNC. Some configuration options can be changed on-the-fly. See annexed 'Configuration Example' for a complete set of configuration options.
79</p>
80<p>
813.1. <a href=#file>File</a><br>
823.2. <a href=#help>Help</a><br>
833.3. <a href=#proxy>Proxy</a><br>
843.4. <a href=#general>General</a><br>
85&nbsp; &nbsp; &nbsp; 3.4.1. <a href=#genlog>Logfile</a><br>
86&nbsp; &nbsp; &nbsp; 3.4.2. <a href=#genapp>Append Files</a><br>
87&nbsp; &nbsp; &nbsp; 3.4.3. <a href=#genconf>Reread Configuration</a><br>
88&nbsp; &nbsp; &nbsp; 3.4.4. <a href=#genstart>Auto Start</a><br>
893.5. <a href=#rinex>RINEX Observations</a><br>
90&nbsp; &nbsp; &nbsp; 3.5.1. <a href=#rnxname>File Names</a><br>
91&nbsp; &nbsp; &nbsp; 3.5.2. <a href=#rnxdir>Directory</a><br>
92&nbsp; &nbsp; &nbsp; 3.5.3. <a href=#rnxinterval>File Interval</a><br>
93&nbsp; &nbsp; &nbsp; 3.5.4. <a href=#rnxsample>Sampling</a><br>
94&nbsp; &nbsp; &nbsp; 3.5.5. <a href=#rnxskl>Skeleton Extension</a><br>
95&nbsp; &nbsp; &nbsp; 3.5.6. <a href=#rnxscript>Script</a><br>
96&nbsp; &nbsp; &nbsp; 3.5.7. <a href=#rnxvers>Version</a><br>
973.6. <a href=#ephemeris>RINEX Ephemeris</a><br>
98&nbsp; &nbsp; &nbsp; 3.6.1. <a href=#ephdir>Directory</a><br>
99&nbsp; &nbsp; &nbsp; 3.6.2. <a href=#ephint>Interval</a><br>
100&nbsp; &nbsp; &nbsp; 3.6.3. <a href=#ephport>Port</a><br>
101&nbsp; &nbsp; &nbsp; 3.6.4. <a href=#ephvers>Version</a><br>
1023.7. <a href=#correct>Ephemeris Corrections</a><br>
103&nbsp; &nbsp; &nbsp; 3.7.1. <a href=#corrdir>Directory</a><br>
104&nbsp; &nbsp; &nbsp; 3.7.2. <a href=#corrint>Interval</a><br>
105&nbsp; &nbsp; &nbsp; 3.7.3. <a href=#corrport>Port</a><br>
106&nbsp; &nbsp; &nbsp; 3.7.4. <a href=#corrwait>Wait for Full Epoch</a><br>
1073.8. <a href=#syncout>Feed Engine</a><br>
108&nbsp; &nbsp; &nbsp; 3.8.1. <a href=#syncport>Port</a><br>
109&nbsp; &nbsp; &nbsp; 3.8.2. <a href=#syncwait>Wait for Full Epoch</a><br>
110&nbsp; &nbsp; &nbsp; 3.8.3. <a href=#syncsample>Sampling</a><br>
111&nbsp; &nbsp; &nbsp; 3.8.4. <a href=#syncfile>File</a><br>
112&nbsp; &nbsp; &nbsp; 3.8.5. <a href=#syncuport>Port (unsynchronized)</a><br>
1133.9. <a href=#serial>Serial Link</a><br>
114&nbsp; &nbsp; &nbsp; 3.9.1. <a href=#sermount>Mountpoint</a><br>
115&nbsp; &nbsp; &nbsp; 3.9.2. <a href=#serport>Port Name</a><br>
116&nbsp; &nbsp; &nbsp; 3.9.3. <a href=#serbaud>Baud Rate</a><br>
117&nbsp; &nbsp; &nbsp; 3.9.4. <a href=#serparity>Parity</a><br>
118&nbsp; &nbsp; &nbsp; 3.9.5. <a href=#serdata>Data Bits</a><br>
119&nbsp; &nbsp; &nbsp; 3.9.6. <a href=#serstop>Stop Bits</a><br>
120&nbsp; &nbsp; &nbsp; 3.9.7. <a href=#serauto>Auto NMEA</a><br>
1213.10. <a href=#advnote>Outages</a><br>
122&nbsp; &nbsp; &nbsp; 3.10.1. <a href=#obsrate>Observation Rate</a><br>
123&nbsp; &nbsp; &nbsp; 3.10.2. <a href=#advfail>Failure Threshold</a><br>
124&nbsp; &nbsp; &nbsp; 3.10.3. <a href=#advreco>Recovery Threshold</a><br>
125&nbsp; &nbsp; &nbsp; 3.10.4. <a href=#pause>Pause</a><br>
126&nbsp; &nbsp; &nbsp; 3.10.5. <a href=#advscript>Script</a><br>
1273.11. <a href=#misc>Miscellaneous</a><br>
128&nbsp; &nbsp; &nbsp; 3.11.1. <a href=#miscmount>Mountpoint</a><br>
129&nbsp; &nbsp; &nbsp; 3.11.2. <a href=#miscperf>Log Latency</a><br>
130&nbsp; &nbsp; &nbsp; 3.11.3. <a href=#miscscan>Scan RTCM</a><br>
1313.12. <a href=#streams>Streams</a><br>
132&nbsp; &nbsp; &nbsp; 3.12.1. <a href=#streamadd>Add Streams</a><br>
133&nbsp; &nbsp; &nbsp; 3.12.2. <a href=#streamhost>Caster Host and Port</a><br>
134&nbsp; &nbsp; &nbsp; 3.12.3. <a href=#streamtable>Caster Table</a><br>
135&nbsp; &nbsp; &nbsp; 3.12.4. <a href=#streamuser>User and Password</a><br>
136&nbsp; &nbsp; &nbsp; 3.12.5. <a href=#streamtable>Get Table</a><br>
137&nbsp; &nbsp; &nbsp; 3.12.6. <a href=#streamntrip>NTRIP Version</a><br>
138&nbsp; &nbsp; &nbsp; 3.12.7. <a href=#streamdelete>Delete Streams</a><br>
139&nbsp; &nbsp; &nbsp; 3.12.8. <a href=#streamedit>Edit Streams</a><br>
140&nbsp; &nbsp; &nbsp; 3.12.9. <a href=#streamconf>Reconfigure Streams On-the-fly</a><br>
1413.13. <a href=#start>Start</a><br>
1423.14. <a href=#stop>Stop</a><br>
1433.15. <a href=#cmd>Command Line Options</a><br>
144&nbsp; &nbsp; &nbsp; 3.15.1. <a href=#nw>No Window Mode</a><br>
145&nbsp; &nbsp; &nbsp; 3.15.2. <a href=#post>Offline Mode</a><br>
146&nbsp; &nbsp; &nbsp; 3.15.3. <a href=#conffile>Configuration File</a><br>
147</p>
148
149<p><a name="file"><h4>3.1. File</h4></p>
150
151<p>
152The 'File' button lets you
153<ul>
154<li> select an appropriate font.<br>
155Use smaller font size if the BNC main window exceeds the size of your screen.
156</li>
157<li> save selected options in configuration file.<br>
158When using 'Save & Activate Options' while BNC is already processing data, some configuration options become immediately effective on-the-fly without interrupting uninvolved threads. See annexed section 'Configuration Example' for a list of on-the-fly changeable configuration options.
159</li>
160<li> quit the BNC program.
161</li>
162</ul>
163</p>
164
165<p><a name="help"><h4>3.2. Help</h4></p>
166
167<p>
168The 'Help' button provides access to
169<ul>
170<li>
171help contents.<br>
172You may keep the 'Help Contents' window open while configuring BNC.
173</li>
174<li>
175a 'Flow Chart' showing BNC linked to a real-time GNSS network engine such as RTNet.
176</li>
177<li>
178general information about BNC.<br>
179Close the 'About BNC' window to continue working with BNC.
180</li>
181</ul>
182</p>
183<p>
184BNC comes with a help system providing online information about its functionality and usage. Short descriptions are available for any widget. Focus to the relevant widget and press Shift+F1 to request help information. A help text appears immediately; it disappears as soon as the user does something else. The dialogs on some operating systems may provide a "?" button that users can click; they then click the relevant widget to pop up the help text.
185</p>
186
187<p><a name="proxy"><h4>3.3. Proxy - for usage in a protected LAN</h4></p>
188
189<p>
190If you are running BNC within a protected Local Area Network (LAN), you might need to use a proxy server to access the Internet. Enter your proxy server IP and port number in case one is operated in front of BNC. If you don't know the IP and port of your proxy server, check the proxy server settings in your Internet browser or ask your network administrator.</p>
191<p>
192Note that IP streaming is often not allowed in a LAN. In this case you need to ask your network administrator for an appropriate modification of the local security policy or for the installation of a TCP relay to the NTRIP broadcasters. If these are not possible, you might need to run BNC outside your LAN on a host that has unobstructed connection to the Internet.
193</p>
194<p><a name="general"><h4>3.4. General</h4></p>
195<p>
196The following defines general settings for BNC's logfile, file handling and reconfiguration on-the-fly.
197</p>
198
199<p><a name="genlog"><h4>3.4.1 Logfile - optional</h4></p>
200<p>
201Records of BNC's activities are shown in the 'Logs' canvas on the bottom of the main window. These logs can be saved into daily logfiles when a valid path is specified in the 'Logfile (full path)' field. The logfile name will automatically be extended by a date string '_YYMMDD' carrying the current date. Message logs cover the communication status between BNC and the NTRIP broadcaster as well as problems that may occur in the communication link, stream availability, stream delay, stream conversion etc. All times are given in UTC. The default value for 'Logfile (full path)' is an empty option field, meaning that BNC logs will not saved into a file.
202</p>
203
204<p><a name="genapp"><h4>3.4.2 Append Files - optional</h4></p>
205<p>
206When BNC is started, new files are created by default and any existing files with the same name will be overwritten. However, users might want to append existing files following a restart of BNC, a system crash or when BNC crashed. Tick 'Append files' to continue with existing files and keep what has been recorded so far. Note that option 'Append files' affects all types of files created by BNC.
207</p>
208
209<p><a name="genconf"><h4>3.4.3 Reread Configuration - optional</h4></p>
210<p>
211When operating BNC online in 'no window' mode (command line option -nw), some configuration options can nevertheless be changed on-the-fly without interrupting the running process. For that you force the program to reread parts of its configuration in pre-defined intervals from the disk. Select '1 min', '1 hour', or '1 day' to let BNC reread on-the-fly changeable configuration options every full minute, hour, or day. This lets in between edited options become effective without interrupting uninvolved threads. See annexed section 'Configuration Example' for a configuration file example and a list of on-the-fly changeable options.
212</p>
213
214<p><a name="genstart"><h4>3.4.4 Auto Start - optional</h4></p>
215<p>
216You may like to auto-start BNC at startup time in window mode with preassigned configuration options. This may be required i.e. immediately after booting your system. Tick 'Auto start' to supersede the usage of the 'Start' button. Make sure that you maintain a link to BNC for that in your Autostart directory (Windows systems) or call BNC in a script below directory /etc/init.d (Unix/Linux/Mac systems).
217</p>
218<p>
219 See BNC's command line option -nw for an auto-start of BNC in 'no window' mode.
220</p>
221
222<p><a name="rinex"><h4>3.5. RINEX Observations</h4></p>
223<p>
224Observations will be converted to RINEX if they come in either RTCM Version 2.x, RTCM Version 3.x, or RTIGS format. BNC's RINEX Observation files generally contain C1, C2, P1, P2, L1, L2, S1, and S2 observations. In case an observation is unavailable, its value is set to zero '0.000'. Note that the 'RINEX TYPE' field in the RINEX Observation file header is always set to 'M(MIXED)' even if the file does not contain any GLONASS or SABAS data.
225</p>
226
227<p><a name="rnxname"><h4>3.5.1 RINEX File Names</h4></p>
228<p>
229RINEX file names are derived by BNC from the first 4 characters of the corresponding stream's mountpoint (4Char Station ID). For example, data from mountpoints FRANKFURT and WETTZELL will have hourly RINEX Observation files named</p>
230<p>
231FRAN{ddd}{h}.{yy}O<br>
232WETT{ddd}{h}.{yy}O
233</p>
234<p>
235where 'ddd' is the day of year, 'h' is a letter which corresponds to an hour long UTC time block and 'yy' is the year.
236</p>
237<p>
238If there are more than one stream with identical 4Char Station ID (same first 4 characters for their mountpoints), the mountpoint strings are split into two sub-strings and both become part of the RINEX file name. For example, when simultaneously retrieving data from mountpoints FRANKFURT and FRANCE, their hourly RINEX Observation files are named as</p>
239<p>
240FRAN{ddd}{h}_KFURT.{yy}O<br>
241FRAN{ddd}{h}_CE.{yy}O.
242</p>
243<p>
244If several streams show exactly the same mountpoint name (example: BRUS0 from <u>www.euref-ip.net</u> and BRUS0 from <u>www.igs-ip.net</u>), BNC adds an integer number to the file name leading i.e. to hourly RINEX Observation files like</p>
245<p>
246BRUS{ddd}{h}_0.{yy}O<br>
247BRUS{ddd}{h}_1.{yy}O.
248</p>
249<p>
250Note that RINEX file names for all intervals less than 1 hour follow the file name convention for 15 minutes RINEX Observation files i.e.</p>
251<p>
252FRAN{ddd}{h}{mm}.{yy}O
253</p>
254<p>
255where 'mm' is the starting minute within the hour.
256</p>
257
258<p><a name="rnxdir"><h4>3.5.2 Directory - optional</h4></p>
259<p>
260Here you can specify the path to where the RINEX Observation files will be stored. If the specified directory does not exist, BNC will not create RINEX Observation files. Default value for 'Directory' is an empty option field, meaning that no RINEX Observation files will be written.
261</p>
262
263<p><a name="rnxinterval"><h4>3.5.3 File Interval - mandatory if 'Directory' is set</h4></p>
264<p>
265Select the length of the RINEX Observation file generated. The default value is 15 minutes.
266</p>
267
268<p><a name="rnxsample"><h4>3.5.4 Sampling - mandatory if 'Directory' is set </h4></p>
269<p>
270Select the RINEX Observation sampling interval in seconds. A value of zero '0' tells BNC to store all received epochs into RINEX. This is the default value.
271</p>
272
273<p><a name="rnxskl"><h4>3.5.5 Skeleton Extension - optional</h4></p>
274<p>
275Whenever BNC starts generating RINEX Observation files (and then once every day at midnight), it first tries to retrieve information needed for RINEX headers from so-called public RINEX header skeleton files which are derived from sitelogs. A HTTP link to a directory containing these skeleton files may be available through data field number 7 of the affected NET record in the source-table. See <u>http://www.epncb.oma.be:80/stations/log/skl/brus.skl</u> for an example of a public RINEX header skeleton file for the Brussels EPN station.
276</p>
277<p>
278However, sometimes public RINEX header skeleton files are not available, its contents is not up to date, or you need to put additional/optional records in the RINEX header. For that BNC allows using personal skeleton files that contain the header records you would like to include. You can derive a personal RINEX header skeleton file from the information given in an up to date sitelog. A file in the RINEX Observations 'Directory' with a 'Skeleton extension' suffix is interpreted by BNC as a personal RINEX header skeleton file for the corresponding stream.
279</p>
280<p>
281Examples for personal skeleton file name convention: RINEX Observation files for mountpoints WETTZELL, FRANKFURT and FRANCE (same 4Char Station ID), BRUS0 from <u>www.euref-ip.net</u> and BRUS0 from <u>www.igs-ip.net</u> (same 4Char Station ID, identical mountpoint stings) would accept personal skeleton files named</p>
282<p>
283WETT.skl<br>
284FRAN_KFURT.skl<br>
285FRAN_CE.skl<br>
286BRUS_0.skl<br>
287BRUS_1.skl</p>
288<p>
289if 'Skeleton extension' is set to 'skl'.
290</p>
291<p>
292Note the following regulations regarding personal RINEX header skeleton files:
293<ul>
294<li>If such a file exists in the 'RINEX directory', the corresponding public RINEX header skeleton file is ignored. The RINEX header is generated solely from the contents of the personal skeleton.</li>
295<li>Personal skeletons should contain a complete first header record of type</li>
296<br>- &nbsp; RINEX VERSION / TYPE
297<li>They should then contain an empty header record of type</li>
298<br>- &nbsp; PGM / RUN BY / DATE
299<br>BNC will complete this line and include it in the actual RINEX file header.
300<li>They should further contain complete header records of type</li>
301<br>- &nbsp; MARKER NAME
302<br>- &nbsp; OBSERVER / AGENCY
303<br>- &nbsp; REC # / TYPE / VERS
304<br>- &nbsp; ANT # / TYPE
305<br>- &nbsp; APPROX POSITION XYZ
306<br>- &nbsp; ANTENNA: DELTA H/E/N
307<br>- &nbsp; WAVELENGTH FACT L1/2
308<li>They may contain any other optional complete header record as defined in the RINEX documentation.</li>
309<li>They should then contain empty header records of type</li>
310<br>- &nbsp; # / TYPES OF OBSERV
311<br>- &nbsp; TIME OF FIRST OBS
312<br>BNC will include these lines in the final RINEX file header together with an additional
313<br>- &nbsp; COMMENT
314<br>line describing the source of the stream.
315<li>They should finally contain an empty header record of type</li>
316<br>- &nbsp; END OF HEADER (last record)
317</ul>
318<p>
319If neither a public nor a personal RINEX header skeleton file is available for BNC, a default header will be used.
320</p>
321
322<p><a name="rnxscript"><h4>3.5.6 Script - optional</h4></p>
323<p>
324Whenever a RINEX Observation file is saved, you might want to compress, copy or upload it immediately via FTP. BNC allows you to execute a script/batch file to carry out these operations. To do that specify the full path of the script/batch file here. BNC will pass the RINEX Observation file path to the script as a command line parameter (%1 on Windows systems, $1 on Unix/Linux/Mac systems).
325</p>
326<p>
327The triggering event for calling the script or batch file is the end of a RINEX Observation file 'Interval'. If that is overridden by a stream outage, the triggering event is the stream reconnection.
328</p>
329<p>
330As an alternative to initiating file uploads through BNC, you may like to call an upload script or batch file through your crontable or Task Scheduler (independent from BNC) once every 2 or 3 minutes after the end of each RINEX file 'Interval'.
331</p>
332
333<p><a name="rnxvers"><h4>3.5.7 Version - optional</h4></p>
334<p>
335The default format for RINEX Observation files is RINEX Version 2.11. Select 'Version 3' if you would like to save observations in RINEX Version 3 format.
336</p>
337
338<p><a name="ephemeris"><h4>3.6. RINEX Ephemeris</h4></p>
339<p>
340Broadcast ephemeris can be saved as RINEX Navigation files when received via RTCM Version 3.x as message types 1019 (GPS) and 1020 (GLONASS) or via RTIGS records type 300. The file name convention follows the details given in section 'RINEX File Names' except that the first four characters are 'BRDC' and the last character is
341</p>
342<ul>
343<li>'N' or 'G' for GPS or GLONASS ephemeris in two separate RINEX Version 2.11 Navigation files, or</li>
344<li>'P' for GPS plus GLONASS ephemeris saved together in one RINEX Version 3 Navigation file.
345</ul>
346
347<p><a name="ephdir"><h4>3.6.1 Directory - optional</h4></p>
348<p>
349Specify the path for saving broadcast ephemeris data as RINEX Navigation files. If the specified directory does not exist, BNC will not create RINEX Navigation files. Default value for Ephemeris 'Directory' is an empty option field, meaning that no RINEX Navigation files will be created.
350</p>
351
352<p><a name="ephint"><h4>3.6.2 Interval - mandatory if 'Directory' is set</h4></p>
353<p>
354Select the length of the RINEX Navigation file generated. The default value is 1 day.
355</p>
356
357<p><a name="ephport"><h4>3.6.3 Port - optional</h4></p>
358<p>
359BNC can output broadcast ephemeris in RINEX Version 3 ASCII format on your local host (IP 127.0.0.1) through an IP 'Port'. This function is introduced in order to support i.e. the 'BKG Ntrip Sate Space Server' (BNS) which transforms IGS clocks and orbits into corrections to broadcast ephemeris. Specify an IP port number to activate this function. The default is an empty option field, meaning that no ASCII ephemeris output via IP port is generated.
360</p>
361<p>
362The source code for BNC comes with an example perl script 'test_bnc_eph.pl' that allows you to read BNC's ASCII ephemeris output from the IP port.
363</p>
364
365<p><a name="ephvers"><h4>3.6.4 Version - optional</h4></p>
366<p>
367Default format for RINEX Navigation files containing broadcast ephemeris is RINEX Version 2.11. Select 'Version 3' if you want to save the ephemeris in RINEX Version 3 format.
368</p>
369<p>
370Note that this does not concern the broadcast ephemeris output throug IP port which is always in RINEX Version 3 format.
371</p>
372
373<p><a name="correct"><h4>3.7. Ephemeris Corrections</h4></p>
374<p>
375</p>
376RTCM is in the process of developing new Version 3 messages to transport satellite clock and orbit corrections in real-time. Based on the latest available proposal, the following premature messages currently under discussion have been implemented in BNC:
377<ul>
378<li>Message type 4050: GPS orbit corrections to Broadcast Ephemeris</li>
379<li>Message type 4051: GPS clock corrections to Broadcast Ephemeris</li>
380<li>Message type 4052: GPS code biases</li>
381<li>Message type 4053: GLONASS orbit corrections to Broadcast Ephemeris</li>
382<li>Message type 4054: GLONASS clock corrections to Broadcast Ephemeris</li>
383<li>Message type 4055: GLONASS code biases</li>
384<li>Message type 4056: Combined orbit and clock corrections to GPS Broadcast Ephemeris</li>
385<li>Message type 4057: Combined orbit and clock corrections to GLONASS Broadcast Ephemeris</li>
386</ul>
387<p>
388RTCM Version 3 streams carrying these messages may be used i.e. to support real-time Precise Point Positioning (PPP) applications.
389</p>
390<p>
391When using clocks from Broadcast Ephemeris (with or without corrections) and clocks from SP3 files in the same application, it is important to understand that Broadcast Ephemeris clocks - according to the Interface Control Documents (ICD) - are corrected for the 2nd-order relativistic effect whereas clocks from SP3 files are not. The 2nd-order relativistic effect is a priodic time correction defined as -2 (R * V) / c^2 and includes the scalar product of satallite position and velocity divided by the speed of light raised to the second power.
392</p>
393
394<p><a name="corrdir"><h4>3.7.1 Directory - optional</h4></p>
395<p>
396Specify a directory for saving Ephemeris Corrections in files. If the specified directory does not exist, BNC will not create Ephemeris Correction files. Default value for Ephemeris Corrections 'Directory' is an empty option field, meaning that no Ephemeris Correction files will be created.
397</p>
398<p>
399The file name convention for Ephemeris Correction files follows the convention for RINEX files except for the last character of the file name suffix which is set to "C".
400</p>
401
402<p><a name="corrint"><h4>3.7.2 Interval - mandatory if 'Directory' is set</h4></p>
403<p>
404Select the length of the Ephemeris Correction files. The default value is 1 day.
405</p>
406
407<p><a name="corrport"><h4>3.7.3 Port - optional</h4></p>
408<p>
409BNC can output epoch by epoch synchronized Ephemeris Corrections in ASCII format on your local host (IP 127.0.0.1) through an IP 'Port'. Specify an IP port number to activate this function. The default is an empty option field, meaning that no Ephemeris Correction output via IP port is generated.
410</p>
411<p>
412The source code for BNC comes with an example perl script 'test_bnc_eph.pl' that allows you to read BNC's Ephemeris Corrections from the IP port. In case of a stream carrying message types 4056 and 4057, the script produces ASCII records containing the following set of parameters:
413</p>
414<p>
415<ul>
416<li>GPS Week</li>
417<li>Second in GPS Week</li>
418<li>GNSS Indicator and Satellite Vehicle Pseudo Random Number</li>
419<li>IOD refering to Broadcast Ephemeris set</li>
420<li>Clock Correction to Broadcast Ephemeris [m]</li>
421<li>Radial Component of Orbit Correction to Broadcast Ephemeris [m]</li>
422<li>Along-track Component of Orbit Correction to Broadcast Ephemeris [m]</li>
423<li>Cross-track Component of Orbit Correction to Broadcast Ephemeris [m]</li>
424<li>Mountpoint</li>
425</ul>
426</p>
427<p>
428The following is an example output from two RTCM Version 3 streams (CLCK1 and CLCK4) containing message types 4056 and 4057:
429<pre>
430...
4311490 115710.0 R17 18 -1.903 2.348 -1.343 -1.403 CLCK1
4321490 115710.0 R10 18 -4.131 2.416 -0.646 -1.054 CLCK1
4331490 115710.0 G27 97 5.291 1.201 -1.964 0.821 CLCK4
4341490 115710.0 G26 14 -11.247 1.003 -1.168 0.074 CLCK4
435...
4361490 115711.0 R17 18 -1.902 2.349 -1.342 -1.403 CLCK1
4371490 115711.0 R10 18 -4.131 2.415 -0.647 -1.052 CLCK1
4381490 115711.0 G27 97 5.288 1.200 -1.964 0.820 CLCK4
4391490 115711.0 G26 14 -11.246 1.004 -1.168 0.074 CLCK4
440...
441</pre>
442</p>
443
444<p><a name="corrwait"><h4>3.7.4 Wait for Full Epoch - mandatory if 'Port' is set</h4></p>
445<p>
446When feeding a real-time GNSS network engine waiting epoch by epoch for synchronized Ephemeris Corrections, BNC drops (only concering IP port output) whatever is received later than 'Wait for full epoch' seconds. A value of 2 to 5 seconds could be an appropriate choice for that, depending on the latency of the incoming Ephemeris Corrections stream and the delay acceptable by your application. A message such as "COCK1: Correction overaged by 5 sec" shows up in BNC's logfile if 'Wait for full epoch' is exceeded.
447</p>
448
449<p><a name="syncout"><h4>3.8. Feed Engine</h4></p>
450<p>
451BNC can generate synchronized or unsynchronized observations epoch by epoch from all stations and satellites to feed a real-time GNSS network engine. The output can be produced in a binary format through an IP port and/or a plain ASCII format to save the observations in a local file. It comprises the following observations where available:</p>
452<p>
453StatID, SVPRN, GPSWeek, GPSWeeks, C1, C2, P1, P2, L1, L2, slip_cnt_L1, slip_cnt_L2, lock_timei_L1, lock_timei_L2, S1, S2, SNR1, SNR2
454</p>
455<p>
456Note that slip_cnt stands for the cumulative loss of continuity indicator, lock_timei for the lock time indicator, and SNR for the signal-to-noise ratio 'S' mapped to integer numbers 1 to 9. In case an observation is not available, its value is set to zero '0.000'. Loss of continuity indicator and lock time indicator are set to nedative values if undefined.
457</p>
458
459<p>The binary output is a continuous stream in the following order:</p>
460<pre>
461begEpoch
462t_obsInternal
463t_obsInternal
464...
465t_obsInternal
466endEpoch
467begEpoch
468t_obsInternal
469...
470</pre>
471
472<p>The corresponding structures are defined as follow:</p>
473<pre>
474 const char begEpoch[] = "BEGEPOCH";
475 const char endEpoch[] = "ENDEPOCH";
476...
477...
478class t_obsInternal {
479 public:
480 int flags;
481 char StatID[20+1]; // Station ID
482 char satSys; // Satellite System ('G' or 'R')
483 int satNum; // Satellite Number (PRN for GPS NAVSTAR)
484 int slot; // Slot Number (for Glonass)
485 int GPSWeek; // Week of GPS-Time
486 double GPSWeeks; // Second of Week (GPS-Time)
487 double C1; // CA-code pseudorange (meters)
488 double C2; // CA-code pseudorange (meters)
489 double P1; // P1-code pseudorange (meters)
490 double P2; // P2-code pseudorange (meters)
491 double L1; // L1 carrier phase (cycles)
492 double L2; // L2 carrier phase (cycles)
493 int slip_cnt_L1; // L1 cumulative loss of continuity indicator (negative value = undefined)
494 int slip_cnt_L2; // L2 cumulative loss of continuity indicator (negative value = undefined)
495 int lock_timei_L1; // L1 last lock time indicator (negative value = undefined)
496 int lock_timei_L2; // L2 last lock time indicator (negative value = undefined)
497 double S1; // L1 signal-to noise ratio
498 double S2; // L2 signal-to noise ratio
499 int SNR1; // L1 signal-to noise ratio (mapped to integer)
500 int SNR2; // L2 signal-to noise ratio (mapped to integer)
501};
502</pre>
503
504<p>
505The source code for BNC comes with an example program called 'test_bnc_qt.cpp' that allows you to read BNC's (synchronized or unsynchronized) binary observation output from the IP port and print the observations in a plain ASCII format on standard output.
506</p>
507<p>
508Note that any socket connection of an application to BNC's synchronized or unsynchronized observations ports is recorded in the 'Logs' canvas on the bottom of the main window together with a connection counter, resulting in log records like 'New client connection on sync/usync port: # 1'.
509</p>
510
511<p><a name="syncport"><h4>3.8.1 Port - optional</h4></p>
512<p>
513BNC can produce synchronized observations in binary format on your local host (IP 127.0.0.1) through an IP 'Port'. Scynchronized means that BNC collects all data for any specific epoch which become available within a certain number of latency seconds (see 'Wait for Full Epoch' option). It then - epoch by epoch - outputs whatever has been received. Specify an IP port number here to activate this function. The default is an empty option field, meaning that no binary synchronized output is generated.</p>
514<p>
515</p>
516
517<p><a name="syncwait"><h4>3.8.2 Wait for Full Epoch - mandatory if 'Port' is set</h4></p>
518<p>
519When feeding a real-time GNSS network engine waiting for synchronized input epoch by epoch, BNC drops whatever is received later than 'Wait for full epoch' seconds. A value of 3 to 5 seconds could be an appropriate choice for that, depending on the latency of the incoming streams and the delay acceptable for your real-time GNSS product. Default value for 'Wait for full epoch' is 5 seconds.
520</p>
521<p>
522Note that 'Wait for full epoch' does not effect the RINEX Observation file content. Observations received later than 'Wait for full epoch' seconds will still be included in the RINEX Observation files.
523</p>
524
525<p><a name="syncsample"><h4>3.8.3 Sampling - mandatory if 'File' or 'Port' is set</h4></p>
526<p>
527Select the synchronized observation output sampling interval in seconds. A value of zero '0' tells BNC to send/store all received epochs. This is the default value.
528</p>
529
530<p><a name="syncfile"><h4>3.8.4 File - optional</h4></p>
531<p>
532Specifies the full path to a 'File' where synchronized observations are saved in plain ASCII format. The default value is an empty option field, meaning that no ASCII output file is created.
533</p>
534<p>
535Beware that the size of this file can rapidly increase depending on the number of incoming streams. This option is primarily meant for testing and evaluation.
536</p>
537
538<p><a name="syncuport"><h4>3.8.5 Port (unsynchronized) - optional</h4></p>
539<p>
540BNC can produce unsynchronized observations from all configured streams in binary format on your local host (IP 127.0.0.1) through an IP 'Port'. Unscynchronized means that BNC immediately forwards any received observation to the port. Specify an IP port number here to activate this function. The default is an empty option field, meaning that no binary unsynchronized output is generated.</p>
541<p>
542
543<p><a name="serial"><h4>3.9. Serial Link</h4></p>
544<p>
545You may use BNC to feed a serial connected device like an GNSS rover. For that one of the incoming streams can be forwarded to a serial port.
546</p>
547
548<p><a name="sermount"><h4>3.9.1 Mountpoint - optional</h4></p>
549<p>
550Enter a 'Mountpoint' to forward its corresponding stream to a serial connected device.
551</p>
552<p>
553When selecting the serial communication options listed below, make sure that you pick those configured to the serial connected device.
554</p>
555
556<p><a name="serport"><h4>3.9.2 Port Name - mandatory if 'Mountpoint' is set</h4></p>
557<p>
558Enter the serial 'Port name' selected on your host for communication with the serial connected device. Valid port names are
559</p>
560<pre>
561Windows: COM1, COM2
562Linux: /dev/ttyS0, /dev/ttyS1
563FreeBSD: /dev/ttyd0, /dev/ttyd1
564Digital Unix: /dev/tty01, /dev/tty02
565HP-UX: /dev/tty1p0, /dev/tty2p0
566SGI/IRIX: /dev/ttyf1, /dev/ttyf2
567SunOS/Solaris: /dev/ttya, /dev/ttyb
568</pre>
569<p>
570Note that you must plug a serial cable in the port defined here before you start BNC.
571</p>
572
573<p><a name="serbaud"><h4>3.9.3 Baud Rate - mandatory if 'Mountpoint' is set</h4></p>
574<p>
575Select a 'Baud rate' for the serial link. Note that using a high baud rate is recommended.
576</p>
577
578<p><a name="serparity"><h4>3.9.4 Parity - mandatory if 'Mountpoint' is set</h4></p>
579<p>
580Select the 'Parity' for the serial link. Note that parity is often set to 'NONE'.
581</p>
582
583<p><a name="serdata"><h4>3.9.5 Data Bits - mandatory if 'Mountpoint' is set</h4></p>
584<p>
585Select the number of 'Data bits' for the serial link. Note that often '8' data bits are used.
586</p>
587
588<p><a name="serstop"><h4>3.9.6 Stop Bits - mandatory if 'Mountpoint' is set</h4></p>
589<p>
590Select the number of 'Stop bits' for the serial link. Note that often '1' stop bit is used.
591</p>
592
593<p><a name="serauto"><h4>3.9.7 Auto NMEA - optional</h4></p>
594<p>
595Tick 'Auto NMEA' to forward NMEA-GGA messages (or any other message) coming from your serial connected device to the NTRIP brodacaster.</p>
596<p>
597This option replaces BNC's simulation of an initial NMEA-GGA message based on approximate latitude/longitude from the broadcaster's source-table. Note that sending valid NMEA-GGA strings (simulated or coming from your serial connected device) to the NTRIP broadcaster is required for receiving virtual reference station (VRS) streams.
598</p>
599
600<p><a name="advnote"><h4>3.10. Outages</h4></p>
601
602<p>
603At various times, the incoming stream might become unavailable or corrupted. In such cases, it is important that the BNC operator and/or the stream providers become aware of the situation so that necessary measures can be taken to restore the stream. Furthermore, continuous attempts to decode corrupted stream(s) can generate unnecessary workload for BNC. Outages and corruptions are handled by BNC as follows:
604</p>
605<p>
606<u>Stream outages:</u> BNC considers a connection to be broken when there are no incoming data detected for more than 20 seconds. When this occurs, BNC will attempt to reconnect at a decreasing rate. It will first try to reconnect with 1 second delay, and again in 2 seconds if the previous attempt failed. If the attempt is still unsuccessful, it will try to reconnect within 4 seconds after the previous attempt and so on. The wait time doubles each time with a maximum wait time of 256 seconds.
607</p>
608<p>
609<u>Stream corruption:</u> Not all bits chunk transfers to BNC's internal decoders return valid observations. Sometimes several chunks might be needed before the next observation can be properly decoded. BNC buffers all the outputs (both valid and invalid) from the decoder for a short time span (size derived from the expected 'Observation rate') and then determines whether a stream is valid or corrupted.
610</p>
611<p>
612Outage and corruption events are reported in the 'Logs' canvas. They can also be passed on as parameters to a shell script or batch file to generate an advisory note to BNC operator or affected stream providers. This functionality lets users utilise BNC as a real-time performance monitor and alarm system for a network of GNSS reference stations.
613</p>
614
615<p><a name="obsrate"><h4>3.10.1 Observation Rate - mandatory if 'Failure threshold', 'Recovery threshold', 'Pause' and 'Script' is set</h4></p>
616<p>
617BNC can collect all returns (success or failure) coming from a decoder within a certain short time span to then decide whether a stream has an outage or its content is corrupted. This procedure needs a rough a priory estimate of the expected observation rate of the incoming streams.</p><p>An empty option field (default) means that you don't want an explicit information from BNC about stream outages and incoming streams that can not be decoded and that the special procedure for handling of corrupted streams is by-passed (decoding attempt will never get paused).
618</p>
619
620<p><a name="advfail"><h4>3.10.2 Failure Threshold - optional</h4></p>
621<p>
622Event 'Begin_Failure' will be reported if no data is received continuously for longer than the 'Failure threshold' time. Similarly, event 'Begin_Corrupted' will be reported when corrupted data is detected by the decoder continuously for longer than this 'Failure threshold' time. The default value is set to 15 minutes and is recommended so not to innundate user with too many event reports.
623</p>
624<p>
625Note that specifying a value of zero '0' for the 'Failure threshold' will force BNC to report any stream failure immediately. Note also that for using this function you need to specify the 'Observation rate'.
626</p>
627
628<p><a name="advreco"><h4>3.10.3 Recovery Threshold - optional</h4></p>
629<p>
630Once a 'Begin_Failure' or 'Begin_Corrupted' event has been reported, BNC will check for when the stream again becomes available or uncorrupted. Event 'End_Failure' or 'End_Corrupted' will be reported as soon as valid observations are again detected continuously throughout the 'Recovery threshold' time span. The default value is set to 5 minutes and is recommended so not to innundate users with too many event reports.
631</p>
632<p>
633Note that specifying a value of zero '0' for the 'Recovery threshold' will force BNC to report any stream recovery immediately. Note also that for using this function you need to specify the 'Observation rate'.
634</p>
635
636<p><a name="pause"><h4>3.10.4 Pause - optional</h4></p>
637<p>
638In case of a corrupted stream, the decoding process can be paused and decodings are then attempted again at decreasing rate. BNC will first attempt to decode again after a 30 second lag and if unsuccessful, make another attempt within 60 seconds after the previous attempt. If it is still unsuccessful, it will make another attempt to decode within 120 seconds after the previous attempt and so on. Each decoding attempt doubles the wait time since the previous attempt. The maximum wait time between attempts is limited to 960 seconds. Tick 'Pause' to activate this function. Note that it is only effective if an 'Observation rate' is specified.
639</p>
640<p>
641Do not tick 'Pause' if you want to prevent BNC from making any decoding pause. Be aware that this may incur an unnecessary workload.
642</p>
643
644<p><a name="advscript"><h4>3.10.5 Script - optional </h4></p>
645<p>
646As mentioned previously, BNC can trigger a shell script or a batch file to be executed when one of the events described are reported. This script can be used to email an advisory note to network operator or stream providers. To enable this feature, specify the full path to the script or batch file in the 'Script' field. The affected stream's mountpoint and type of event reported ('Begin_Outage', 'End_Outage', 'Begin_Corrupted' or 'End_Corrupted') will then be passed on to the script as command line parameters (%1 and %2 on Windows systems or $1 and $2 on Unix/Linux/Mac systems) together with date and time information.
647</p>
648<p>
649Leave the 'Script' field empty if you do not wish to use this option. An invalid path will also disable this option.
650</p>
651<p>
652Examples for command line parameter strings passed on to the advisory 'Script' are:
653<pre>
654FFMJ0 Begin_Outage 08-02-21 09:25:59
655FFMJ0 End_Outage 08-02-21 11:36:02 Begin was 08-02-21 09:25:59
656</pre>
657Sample script for Unix/Linux/Mac systems:
658<pre>
659#!/bin/bash
660sleep $((60*RANDOM/32767))
661cat | mail -s "NABU: $1" email@address &lt;&lt;!
662Advisory Note to BNC User,
663Please note the following advisory received from BNC.
664Stream: $*
665Regards, BNC
666!
667</pre>
668</p>
669<p>
670Note the sleep command in this script which causes the system to wait for a random period of up to 60 seconds before sending the email. This should avoids overloading your mail server in case of a simultaneous failure of many streams.
671</p>
672
673<p><a name="misc"><h4>3.11. Miscellaneous</h4></p>
674<p>
675This section describes a number of miscellaneous options which can be applied for a single stream (mountpoint) or for all configured streams.
676</p>
677
678<p><a name="miscmount"><h4>3.11.1 Mountpoint - optional </h4></p>
679<p>
680Specify a mountpoint to apply one or several of the 'Miscellaneous' options to the corresponding stream. Enter 'ALL' if you want to apply these options to all configured streams. An empty option field (default) means that you don't want BNC to apply any of these options.
681</p>
682
683<p><a name="miscperf"><h4>3.11.2 Log Latency - optional </h4></p>
684<p>
685 BNC can average latencies per stream over a certain period of GPS time, the 'Performance log' interval. Mean latencies are calculated from the individual latencies of at most one (first incoming) observation or correction to Broadcast Ephemeris per second. Note that computing correct latencies requires the clock of the host computer to be properly synchronized.
686</p>
687<p>
688<u>Latency:</u> Latency is defined in BNC by the following equation:
689</p>
690<pre>
691 UTC time provided by BNC's host
692 - GPS time of currently processed epoch
693 + Leap seconds between UTC and GPS time
694 --------------
695 = Latency
696</pre>
697<p>
698<u>Statistics:</u> BNC counts the number of GPS seconds covered by at least one observation. It also estimates an observation rate (independent from the a priory specified 'Observation rate') from all observations received throughout the first full 'Performance log' interval. Based on this rate, BNC estimates the number of data gaps when appearing in subsequent intervals.
699</p>
700<p>
701Latencies of observations or corrections to Broadcast Ephemeris and statistical information can be recorded in the 'Logs' canvas at the end of each 'Performance log' interval. A typical output from a 1 hour 'Performance log' interval would be:
702</p>
703<pre>
70408-03-17 15:59:47 BRUS0: Mean latency 1.47 sec, min 0.66, max 3.02, rms 0.35, 3585 epochs, 15 gaps
705</pre>
706<p>
707Select a 'Performance log' interval to activate this function or select the empty option field if you do not want BNC to log latencies and statistical information.
708</p>
709
710
711<p><a name="miscscan"><h4>3.11.3 Scan RTCM - optional</h4></p>
712<p>
713When configuring a GNSS receiver for RTCM stream generation, the setup interface may not provide details about RTCM message types. As reliable information concerning stream contents should be available i.e. for NTRIP broadcaster operators to maintain the broadcaster's source-table, BNC allows to scan RTCM streams for incoming message types and printout some of the contained meta-data. The idea for this option arose from 'InspectRTCM', a comprehensive stream analyzing tool written by D. Stoecker.
714</p>
715<p>
716Tick 'Scan RTCM' to scan RTCM Version 2.x or 3.x streams and log all contained
717</p>
718<ul>
719<li>numbers of incoming message types</li>
720<li>Antenna Reference Point (ARP) coordinates</li>
721<li>Antenna Phase Center (APC) coordinates</li>
722<li>antenna height above marker</li>
723<li>antenna descriptor.</li>
724</ul>
725</p>
726
727<p>
728Note that in RTCM Version 2.x the message types 18 and 19 carry only the observables of one frequence. Hence it needs two type 18 and 19 messages per epoch to transport the observations from dual frequency receivers.
729</p>
730<p>
731
732<p>Logged time stamps refer to message reception time and allow to understand repetition rates. Enter 'ALL' if you want to log this information from all configured streams. Beware that the size of the logfile can rapidly increase depending on the number of incoming RTCM streams.
733</p>
734<p>This option is primarily meant for testing and evaluation. Use it to figure out what exactly is produced by a specific GNSS receiver's configuration. An empty option field (default) means that you don't want BNC to print the message type numbers and antenna information carried in RTCM streams.
735</p>
736
737<p><a name="streams"><h4>3.12. Streams</h4></p>
738<p>
739Each stream on an NTRIP broadcaster is defined using a unique source ID called mountpoint. An NTRIP client like BNC access the desired data stream by referring to its mountpoint. Information about streams and their mountpoints is available through the source-table maintained by the NTRIP broadcaster. Note that mountpoints could show up in BNC more than once when retrieving streams from several NTRIP broadcasters.
740</p>
741
742<p>
743Streams selected for retrieval are listed under the 'Streams' canvas section on BNC's main window. The list provides the following information extracted from source-table(s) produced by the NTRIP broadcasters:
744</p>
745
746<table>
747<tr><td>'broadcaster:port'&nbsp; </td><td>NTRIP broadcaster URL and port.</td></tr>
748<tr><td>'mountpoint' &nbsp;</td><td>Mountpoint on NTRIP broadcaster.</td></tr>
749<tr><td>'decoder' &nbsp;</td><td>Type of decoder used to handle the incoming stream content according to its format; editable.</td></tr>
750<tr><td>'lat' &nbsp;</td><td>Approximate latitude of reference station, in degrees, north; editable if 'nmea' = 'yes'.</td></tr>
751<tr><td>'long' &nbsp;</td><td>Approximate longitude of reference station, in degrees, east; editable if 'nmea' = 'yes'.</td></tr>
752<tr><td>'nmea' &nbsp;</td><td>Indicates whether or not streaming needs to be initiated by BNC through sending NMEA-GGA message carrying position coordinates in 'lat' and 'long'.</td></tr>
753<tr><td>'ntrip' &nbsp;</td><td>Selected NTRIP transport protocol version.</td></tr>
754<tr><td>'bytes' &nbsp;</td><td>Number of bytes retrieved.
755</table>
756
757<p><a name="streamadd"><h4>3.12.1 Add Streams</h4></p>
758<p>
759Button 'Add Streams' opens a window that allows user to select data streams from an NTRIP broadcaster according to their mountpoints.
760</p>
761
762<p><a name="streamhost"><h4>3.12.2 Caster Host and Port - mandatory</h4></p>
763<p>
764Enter the NTRIP broadcaster host IP and port number. Note that EUREF and IGS operate NTRIP broadcasters at <u>http://www.euref-ip.net/home</u> and <u>http://www.igs-ip.net/home</u>.
765</p>
766
767<p><a name="streamtable"><h4>3.12.3 Caster Table - optional</h4></p>
768<p>
769It may be that your are not sure about your NTRIP broadcasters host and port number or you are interested in other broadcaster installations operated elsewhere. Hit 'Show' for a table of known broadcasters maintained at <u>www.rtcm-ntrip.org/home</u>. A window opens which allows to select a broadcaster for stream retrieval.
770</p>
771
772<p><a name="streamuser"><h4>3.12.4 User and Password - mandatory for protected streams</h4></p>
773<p>
774Some streams on NTRIP broadcasters may be restricted. Enter a valid 'User' ID and 'Password' for access to protected streams. Accounts are usually provided per NTRIP broadcaster through a registration procedure. Register through <u>http://igs.bkg.bund.de/index_ntrip_reg.htm</u> for access to protected streams on <u>www.euref-ip.net</u> and <u>www.igs-ip.net</u>.
775</p>
776
777<p><a name="streamtable"><h4>3.12.5 Get Table</h4></p>
778<p>
779Use the 'Get Table' button to download the source-table from the NTRIP broadcaster. Pay attention to data fields 'format' and 'format-details'. Keep in mind that BNC can only decode and convert streams that come in RTCM Version 2.x, RTCM Version 3.x, or RTIGS format. RTCM Version 2.x streams must contain message types 18 and 19 or 20 and 21 while RTCM Version 3.x streams must contain GPS or SBAS message types 1002 or 1004 and may contain GLONASS message types 1010 or 1012, see data field 'format-details' for available message types and their repetition rates in brackets. Note that in order to produce RINEX Navigation files RTCM Version 3.x streams containing message types 1019 (GPS) and 1020 (GLONASS) are required. Select your streams line by line, use +Shift and +Ctrl when necessary.
780</p>
781<p>
782The contents of data field 'nmea' tells you whether a stream retrieval needs to be initiated by BNC through sending an NMEA-GGA message carrying approximate position coordinates (virtual reference station).
783</p>
784<p>
785Hit 'OK' to return to the main window. If you wish you can click on 'Add Streams' and repeat the process again to retrieve streams from different casters.
786</p>
787
788<p><a name="streamntrip"><h4>3.12.6 NTRIP Version - mandatory</h4></p>
789<p>
790Some limitations and deficiencies of the NTRIP version 1 stream transport protocol are solved in NTRIP version 2. Improvements mainly concern a full HTTP compatibility in view of requirements coming from proxy servers. Version 2 is backwards compatible to Version 1. Options implemented in BNC are:
791</p>
792<p>
793&nbsp; 1:&nbsp; NTRIP version 1, TCP/IP.<br>
794&nbsp; 2:&nbsp; NTRIP version 2 in TCP/IP mode.<br>
795&nbsp; R:&nbsp; NTRIP version 2 in RTSP/RTP mode.
796</p>
797<p>
798If NTRIP version 2 is supported by the broadcaster:
799</p>
800<ul>
801<li>Try using option '2' if your streams are otherwise blocked by a proxy server operated in front of BNC.</li>
802<li>Option 'R' may be selected if latency is more important than completeness for your application. Note that the latency reduction is likely to be in the order of 0.5 sec or less. Note further that option 'R' (RTSP/RTP mode) is not accepted by proxy servers and a mobile Internet Service Provider may not support it.</li>
803</ul>
804<p>
805Select option '1' if you are not sure whether the broadcaster supports NTRIP version 2.</li>
806</p>
807
808<p><a name="streamdelete"><h4>3.12.7 Delete Streams</h4></p>
809<p>
810To remove a stream from the 'Streams' canvas in the main window, highlight it by clicking on it and hit the 'Delete Streams' button. You can also remove multiple streams simultaneously by highlighting them using +Shift and +Ctrl.</p>
811
812<p><a name="streamedit"><h4>3.12.8 Edit Streams</h4></p>
813<ul>
814<li>
815BNC automatically allocates one of its internal decoders to a stream based on the stream's 'format' and 'format-details' as given in the source-table. However, there might be cases where you need to override the automatic selection due to incorrect source-table for example. BNC allows users to manually select the required decoder by editing the decoder string. Double click on the 'decoder' field, enter your preferred decoder and then hit Enter. The accepted decoder strings are 'RTCM_2.x', 'RTCM_3.x', and 'RTIGS'.
816</li>
817<li>
818In case you need to log the raw data as is, BNC allows users to by-pass its decoders and and directly save the input in daily log files. To do this specify the decoder string as 'ZERO'. The generated file names are created from the characters of the streams mountpoints plus two-digit numbers each for year, month, and day. Example: Setting the 'decoder' string for mountpoint WTZZ0 to 'ZERO' and running BNC on March 29, 2007 would save the raw data in a file named WTZZ0_070329.
819</li>
820<li>
821BNC can also retrieve streams from virtual reference stations (VRS). To initiate these streams, an approximate rover position needs to be sent in NMEA format to the NTRIP broadcaster. In return, a user-specific data stream is generated, typically by a Network-RTK software. VRS streams are indicated by a 'yes' in the source-table as well as in the 'nmea' column on the 'Streams' canvas in BNC's main window. They are customized exactly to the latitude and longitude transmitted to the NTRIP broadcaster via NMEA-GGA messages.
822<br>If NMEA-GGA messages are not coming from a serial connected GNSS rover, BNC simulates them from the default latitude and longitude of the source-table as shown in the 'lat' and 'long' columns on the 'Streams' canvas. However, in most cases you would probably want to change these defaults according to your requirement. Double-click on 'lat' and 'long' fields, enter the values you wish to send and then hit Enter. The format is in positive north latitude degrees (e.g. for northern hemisphere: 52.436, for southern hemisphere: -24.567) and eastern longitude degrees (example: 358.872 or -1.128). Only streams with a 'yes' in their 'nmea' column can be edited. The position must preferably be a point within the VRS service area of the network. RINEX files generated from these streams will contain an additional COMMENT line in the header beginning with 'NMEA' showing the 'lat' and 'long' used.
823<br>Note that when running BNC in a Local Area Network (LAN), NMEA strings may be blocked by a proxy server, firewall or virus scanner.
824</li>
825</ul>
826
827<p><a name="streamconf"><h4>3.12.9 Reconfigure Streams On-the-fly</h4></p>
828<p>
829The streams selection can be changed on-the-fly without interrupting uninvolved threads in the running BNC process.
830</p>
831<p>
832<u>Window mode:</u> Hit 'Save & Activate Options' while BNC is in window mode and already processing data to let changes of your streams selection immediately become effective.
833<p>
834<u>No window mode:</u> When operating BNC online in 'no window' mode (command line option -nw), you force BNC to reread its 'mountPoints' configuration option from disk at pre-defined intervals. Select '1 min', '1 hour', or '1 day' as 'Reread configuration' option to reread the 'mountPoints' option every full minute, hour, or day. This lets a 'mountPoints' option edited in between in the configuration file become effective without terminating uninvolved threads. See annexed section 'Configuration Example' for a configuration file example and a list of other on-the-fly changeable options.
835</p>
836
837<p><a name="start"><h4>3.13. Start</h4></p>
838<p>
839Hit 'Start' to start retrieving, decoding, and converting GNSS data streams in real-time. Note that 'Start' generally forces BNC to begin with fresh RINEX which might overwrite existing files when necessary unless the option 'Append files' is ticked.
840</p>
841
842<p><a name="stop"><h4>3.14. Stop</h4></p>
843<p>
844Hit the 'Stop' button in order to stop BNC.
845</p>
846
847<p><a name="cmd"><h4>3.15. Command Line Options</h4></p>
848<p>
849Command line options are available to run BNC in 'no window' mode or let it read data from a file in offline mode. BNC will then use processing options from the configuration file. Note that the self-explaining contents of the configuration file can easily be edited. It is possible to introduce a specific configuration file name instead of using the default name 'BNC.ini'.
850</p>
851
852<p><a name="nw"><h4>3.15.1 No Window Mode - optional</h4></p>
853<p>
854Apart from its regular windows mode, BNC can be started on all systems as a background/batch job with command line option '-nw'. BNC will then run in 'no window' mode, using processing options from its configuration file on disk. Terminate BNC using Windows Task Manager when running it in 'no window' mode on Windows systems.
855</p>
856<p>
857Example:<br><br>
858bnc.exe -nw
859</p>
860
861<p><a name="post"><h4>3.15.2 Offline Mode - optional</h4></p>
862<p>
863Although BNC is primarily a real-time online tool, it can be run in offline mode to read data from a file for post processing purposes. Enter the following four command line options for that:
864</p>
865<p>
866<ul>
867<li>'--file &#060;<u>inputFileName</u>&#062;' to enter the full path to an input file containing data in RTCM Version 2.x, or Version 3.x, or RTIGS/SOC format.</li>
868<li>'--format &#060;<u>format</u>&#062;' to enter one of the file format describing strings 'RTCM_2', 'RTCM_3' or 'RTIGS'.</li>
869<li>'--date YYYY-MM-DD' to enter a date for the first epoch.</li>
870<li>'--time HH:MM:SS' to enter a time for the first epoch.</li>
871</ul>
872<p>
873Example:<br><br>
874./bnc --file FFMJ.dat --format RTCM_3 --date 2008-10-27 --time 23:12:56
875</p>
876<p>
877Note that it is necessary to define a date and time for the first epoch because RTCM streams do not contain complete time stamps as needed for RINEX. Note further that when running BNC in offline mode, it will use options for file saving, interval, sampling etc. from its configuration file.
878</p>
879
880<p><a name="conffile"><h4>3.15.3 Configuration File - optional</h4></p>
881The default configuration file name is 'BNC.ini'. You may change this name at startup time using the command line option '--conf &#060;<u>confFileName</u>&#062;'. This allows to run several BNC jobs in parallel on the same host using different sets of configuration options. <u>confFileName</u> stands either for the full path to a configuration file or just for a file name. If you introduce only a filename, the corresponding file will be saved in the current working directory from where BNC is started.
882</p>
883<p>
884Example:<br><br>
885./bnc --conf MyConfig.ini
886</p>
887<p>
888This leads to a BNC job using configuration file 'MyConfig.ini'. The configuration file will be saved in the current working directory.
889</p>
890
891<p><a name="limits"><h3>4. Limitations</h3></p>
892<ul>
893<li>
894In Qt-based desktop environments (like KDE) on Unix/Linux platforms it may happen that you experience a crash of BNC at startup even when running the program in the background using the '-nw' option. This is a known bug most likely resulting from an incompatibility of Qt libraries in the environment and in BNC. Entering the command 'unset SESSION_MANAGER' before running BNC may help as a work-around.
895</li>
896<li>
897Currently BNC only handles GPS, SBAS and GLONASS data. Galileo is not yet supported.
898</li>
899<li>
900BNC currently will only handle C1, C2, P1, P2, L1, L2, S1, and S2 observations as well as the cumulative loss of continuity and lock time indicators. Which observables and indicators are available on a particular stream will depend on the setup of source receiver and the data format used. RTCM Version 2.x streams do not carry signal-to-noise ratio 'S' values while RTCM Version 3.x streams can only transport one code observable per frequency. Note that signal-to-noise ratios 'S' are also logged mapped to integer numbers 1 to 9.
901</li>
902<li>
903Using RTCM Version 3.x, BNC will properly handle message types 1002, 1004, 1010, and 1012. Note that when handling message types 1001, 1003, 1009 and 1011 where the ambiguity field is not set, the output will be no valid RINEX. All values will be stored modulo 299792.458 (speed of light).
904</li>
905Concerning the length of data fields in RTCM Version 3.x premature message types 4056 and 4057 (combined orbit and clock corrections to GPS and GLONASS Broadcast Ephemeris, see RTCM document 026-2008-SC104-429 'Version 1 Proposed SSR Messages prepared by Geo++'). A final decision on his is not yet available. Note the what's implemented in BNC is just a temporary solutions.
906<li>
907Using RTCM Version 2.x, BNC will only handle message types 18 and 19 or 20 and 21 together with position and the antenna offset information carried in types 3 and 22. Note that processing carrier phase corrections and pseudo-range corrections contained in message types 20 and 21 needs access to broadcast ephemeris. Hence, whenever dealing with message types 20 and 21, make sure that broadcast ephemeris become available for BNC through also retrieving at least one RTCM Version 3.x stream carrying message types 1019 (GPS ephemeris) and 1020 (GLONASS ephemeris).
908</li>
909<li>
910Streams coming in RTIGS format carry only GPS data.
911</li>
912<li>
913BNC's 'Get Table' function only shows the STR records of a source-table. You can use an Internet browser to download the full source-table contents of any NTRIP broadcaster by simply entering its URL in the form of http://host:port. Data field number 8 in the NET records may provide information about where to register for an NTRIP broadcaster account.
914</li>
915<li>
916EUREF as well as IGS adhere to an open data policy. Streams are made available through NTRIP broadcasters at <u>www.euref-ip.net</u> and <u>www.igs-ip.net</u> free of charge to anyone for any purpose. There is no indication up until now how many users will need to be supported simultaneously. The given situation may develop in such a way that it might become difficult to serve all registered users at the same times. In cases where limited resources on the NTRIP broadcaster side (software restrictions, bandwidth limitation etc.) dictates, first priority in stream provision will be given to stream providers followed by re-broadcasting activities and real-time analysis centers while access to others might be temporarily denied.
917</li>
918<li>
919We experienced a limitation of the Standard Version of Microsoft Windows related to socket communication where sockets are not always handled properly. Since BNC makes intensive use of communication through sockets, we recommend to use the Server Version of Microsoft Windows when running BNC continuously for extended on a Windows platform.
920</li>
921<li>
922The source code provided by NRCan for decoding RTIGS streams is 32-bit dependent. Hence the BNC executable generated for 64-bit Linux systems would only run when compiled using the -m32 compiler option.
923</li>
924<li>
925Once BNC has been started, many of its configuration options can not be changed as long as it is stopped. See chapter 'Reread Configuration' for on-the-fly configuration exceptions.
926</li>
927<br>
928</ul>
929<p><a name="authors"><h3>5. Authors</h3></p>
930<p>
931The BKG Ntrip Client (BNC) Qt Graphic User Interface (GUI) has been developed for the Federal Agency for Cartography and Geodesy (BKG) by Leos Mervart, Czech Technical University Prague, Department of Geodesy. BNC includes the following GNU GPL software components:
932<ul>
933<li> RTCM 2.x decoder, written by Oliver Montenbruck, German Space Operations Center, DLR, Oberpfaffenhofen</li>
934<li> RTCM 3.x decoder, written for BKG by Dirk Stoecker, Alberding GmbH, Schoenefeld</li>
935<li> RTIGS decoder, written by Ken MacLeod, Natural Resources, Canada.</li>
936</ul>
937</p>
938<p>
939Georg Weber<br>
940Federal Agency for Cartography and Geodesy (BKG)<br>
941Frankfurt, Germany<br>
942[euref-ip@bkg.bund.de] or [igs-ip@bkg.bund.de]
943</p>
944<p>
945<b>Acknowledgements</b><br>
946BNC's Help Contents has been proofread by Thomas Yan, University of New South Wales, Australia.<br>
947Scott Glazier, OmniSTAR Australia, included the decoding of broadcast ephemeris from RTIGS streams and has been helpful in finding BNC's bugs.<br>
948James Perlt, BKG, helped fixing bugs and redesigned BNC's main window.<br>
949Andre Hauschild, German Space Operations Center, DLR, revised the RTCMv2 decoder.<br>
950Zdenek Lukes, Czech Technical University Prague, Department of Geodesy, extended the RTCMv2 decoder to handle message types 3, 20, 21, and 22 and added loss of lock indicator.<br>
951</p>
952
953<p><a name="annex"><h3>8. Annex</h3></p>
954<p>
9558.1. <a href=#history>History</a><br>
9568.2. <a href=#rtcm>RTCM</a><br>
957&nbsp; &nbsp; &nbsp; 8.2.1 NTRIP <a href=#ntrip1>Version 1</a><br>
958&nbsp; &nbsp; &nbsp; 8.2.2 NTRIP <a href=#ntrip2>Version 2</a><br>
959&nbsp; &nbsp; &nbsp; 8.2.3 RTCM <a href=#rtcm2>Version 2.x</a><br>
960&nbsp; &nbsp; &nbsp; 8.2.4 RTCM <a href=#rtcm3>Version 3.x</a><br>
9618.3. <a href=#rtigs>RTIGS</a><br>
962&nbsp; &nbsp; &nbsp; 8.3.1 <a href=#soc>SOC</a><br>
9638.4. <a href=#config>Configuration Example</a><br>
9648.5. <a href=#links>Links</a><br>
965</p>
966
967<p><a name=history><h3>8.1 History</h3></p>
968<table>
969<tr></tr>
970<tr><td>Dec 2006 &nbsp;</td><td>Version 1.0b &nbsp;</td><td>[Add] First Beta Binaries published based on Qt 4.2.3.</td></tr>
971<tr><td>Jan 2007 &nbsp;</td><td>Version 1.1b &nbsp;</td><td>[Add] Observables C2, S1, and S2<br>[Add] Virtual reference station access<br>[Bug] RTCM2 decoder time tag fixed<br>[Mod] Small letters for public RINEX skeleton files<br>[Add] Online help through Shift+F1</td></tr>
972<tr><td>Apr 2007 &nbsp;</td><td>Version 1.2b &nbsp;</td><td>[Bug] Output only through IP port<br>[Bug] Method 'reconnecting' now thread-save<br> [Add] ZERO decoder added<br> [Mod] Download public RINEX skeletons once per day<br> [Mod] Upgrade to Qt Version 4.2.3<br> [Mod] Replace 'system' call for RINEX script by 'QProcess'<br> [Add] HTTP Host directive for skeleton file download<br> [Add] Percent encoding for user IDs and passwords<br> [Bug] Exit execution of calling thread for RTCM3 streams<br> [Bug] Signal-slot mechanism for threads</td></tr>
973<tr><td>May 2007 &nbsp;</td><td>Version 1.3 &nbsp;</td><td>[Add] Source code published.
974<tr><td>Jul 2007 &nbsp;</td><td>Version 1.4 &nbsp;</td><td>[Bug] Skip messages from proxy server<br> [Bug] Call RINEX script through 'nohup'</td></tr>
975<tr><td>Apr 2008 &nbsp;</td><td>Version 1.5 &nbsp;</td><td>[Add] Handle ephemeris from RTCM Version 3.x streams<br> [Add] Upgrade to Qt Version 4.3.2<br> [Add] Optional RINEX v3 output<br> [Add] SBAS support<br> [Bug] RINEX skeleton download following stream outage<br> [Add] Handle ephemeris from RTIGS streams<br> [Add] Monitor stream failure/recovery and latency<br> [Mod] Redesign of main window<br> [Bug] Freezing of About window on Mac systems<br> [Bug] Fixed problem with PRN 32 in RTCMv2 decoder<br> [Bug] Fix for Trimble 4000SSI receivers in RTCMv2 decoder<br> [Mod] Major revision of input buffer in RTCMv2 decoder</td></tr>
976<tr><td>Dec 2008 &nbsp;</td><td>Version 1.6 &nbsp;</td><td>[Mod] Fill blanc columns in RINEXv3 with 0.000<br> [Add] RTCMv3 decoder for clock and orbit corrections<br>[Add] Check RTCMv3 streams for incoming message types<br> [Add] Decode RTCMv2 message types 3, 20, 21, and 22<br> [Add] Loss of lock and lock time indicator<br> [Bug] Rounding error in RTCMv3 decoder concerning GLONASS height<br> [Mod] Accept GLONASS in RTCMv3 when transmitted first<br> [Add] Leap second 1 January 2009<br> [Add] Offline mode, read data from file<br> [Add] Output antenna descriptor, coordinates and excentricities from RTCMv3<br> [Add] Reconfiguration on-the-fly<br> [Mod] Binary ouput of synchronized observations<br> [Add] Binary output of unsynchronized observations<br> [Bug] Fixed problem with joined RTCMv3 blocks</td></tr>
977<tr><td>Feb 2009 &nbsp;</td><td>Version 1.7 &nbsp;</td><td>[Mod] NTRIP v1 source-table request<br> [Bug] RINEX navigation file format <br> [Add] Upgrade to Qt Version 4.4.3<br> [Add] Support of NTRIP v2<br> [Add] Rover support via serial port<br> [Add] Show broadcaster table from www.rtcm-ntrip.org<br> [Add] Enable/disable tab widgets<br> [Add] User defined configuration file name<br> [mod] Switch to configuration files in iniFormat<br> [Add] Daily logfile rotation</td></tr>
978</table>
979</p>
980
981<p><a name="rtcm"><h4>8.2. RTCM</h4></p>
982
983<p>
984The Radio Technical Commission for Maritime Services (RTCM) is an international non-profit scientific, professional and educational organization. Special Committees provide a forum in which governmental and non-governmental members work together to develop technical standards and consensus recommendations in regard to issues of particular concern. RTCM is engaged in the development of international standards for maritime radionavigation and radiocommunication systems. The output documents and reports prepared by RTCM Committees are published as RTCM Recommended Standards. Topics concerning Differential Global Navigation Satellite Systems (DGNSS) are handled by the Special Committee SC 104.
985<p>
986Personal copies of RTCM Recommended Standards can be ordered through <u>http://www.rtcm.org/orderinfo.php</u>.
987</p>
988
989<p><a name="ntrip1"><h4>8.2.1 NTRIP Version 1</h4></p>
990
991<p>
992'Networked Transport of RTCM via Internet Protocol' Version 1.0 (NTRIP) stands for an application-level protocol streaming Global Navigation Satellite System (GNSS) data over the Internet. NTRIP is a generic, stateless protocol based on the Hypertext Transfer Protocol HTTP/1.1. The HTTP objects are enhanced to GNSS data streams.
993</p>
994
995<p>
996NTRIP Version 1.0 is an RTCM standard designed for disseminating differential correction data (e.g. in the RTCM-104 format) or other kinds of GNSS streaming data to stationary or mobile users over the Internet, allowing simultaneous PC, Laptop, PDA, or receiver connections to a broadcasting host. NTRIP supports wireless Internet access through Mobile IP Networks like GSM, GPRS, EDGE, or UMTS.
997</p>
998
999<p>
1000NTRIP is implemented in three system software components: NTRIP clients, NTRIP servers and NTRIP broadcasters. The NTRIP broadcaster is the actual HTTP server program whereas NTRIP client and NTRIP server are acting as HTTP clients.
1001</p>
1002
1003<p>
1004NTRIP is an open none-proprietary protocol. Major characteristics of NTRIP's dissemination technique are:
1005<ul>
1006<li>Based on the popular HTTP streaming standard; comparatively easy to implement when having limited client and server platform resources available.</li>
1007<li>Application not limited to one particular plain or coded stream content; ability to distribute any kind of GNSS data.</li>
1008<li>Potential to support mass usage; disseminating hundreds of streams simultaneously for thousands of users possible when applying modified Internet Radio broadcasting software.</li>
1009<li>Considering security needs; stream providers and users don't necessarily get into contact, streams often not blocked by firewalls or proxy servers protecting Local Area Networks.</li>
1010<li>Enables streaming over mobile IP networks because of using TCP/IP.</li>
1011</ul>
1012</p>
1013
1014<p>
1015The NTRIP broadcaster maintains a source-table containing information on available NTRIP streams, networks of NTRIP streams and NTRIP broadcasters. The source-table is sent to an NTRIP client on request. Source-table records are dedicated to one of the following: Data Streams (record type STR), Casters (record type CAS), or Networks of streams (record type NET).
1016</p>
1017
1018<p>
1019Source-table records of type STR contain the following data fields: 'mountpoint', 'identifier', 'format', 'format-details', 'carrier', 'nav-system', 'network', 'country', 'latitude', 'longitude', 'nmea', 'solution', 'generator', 'compr-encryp', 'authentication', 'fee', 'bitrate', 'misc'.
1020</p>
1021<p>
1022Source-table records of type NET contain the following data fields: 'identifiey', 'operator', 'authentication', 'fee', 'web-net', 'web-str', 'web-reg', 'misc'.
1023</p>
1024<p>
1025Source-table records of type CAS contain the following data fields: 'host', 'port', 'identifier', 'operator', 'nmea', 'country', 'latitude', 'longitude', 'misc'.
1026</p>
1027
1028<p><a name="ntrip2"><h4>8.2.1 NTRIP Version 2</h4></p>
1029
1030<p>
1031The major changes of NTRIP version 2.0 compared to version 1.0 are:
1032</p>
1033
1034<ul>
1035<li>cleared and fixed design problems and HTTP protocol violations;</li>
1036<li>replaced non standard directives;</li>
1037<li>chunked transfer encoding;</li>
1038<li>improvements in header records;</li>
1039<li>sourcetable filtering; and</li>
1040<li>RTSP communication.</li>
1041</ul>
1042
1043<p>NTRIP version 2 allows to either communicate in TCP/IP mode or in RTSP/RTP mode whereas version 1 is limited to TCP/IP only.
1044</p>
1045
1046<p><a name="rtcm2"><h4>8.2.3 RTCM Version 2.x</h4></p>
1047<p>
1048Transmitting GNSS carrier phase data can be done through RTCM Version 2.x messages. Please note that only RTCM Version 2.2 and 2.3 streams may include GLONASS data. Messages that may be of some interest here are:
1049</p>
1050
1051<ul>
1052<li>
1053Type 1 message is the range correction message and is the primary message in code-phase differential positioning (DGPS). It is computed in the base receiver by computing the error in the range measurement for each tracked SV.
1054</li>
1055<li>
1056Type 2 message is automatically generated when a new set of satellite ephemeris is downloaded to the base receiver. It is the computed difference between the old ephemeris and the new ephemeris. Type 2 messages are used when the base station is transmitting Type 1 messages.
1057</li>
1058<li>
1059Type 3 and 22 messages are the base station position and the antenna offset. Type 3 and 22 are used in RTK processing to perform antenna reduction.
1060</li>
1061<li>
1062Type 6 message is a null frame filler message that is provided for data links that require continuous transmission of data, even if there are no corrections to send. As many Type 6 messages are sent as required to fill in the gap between two correction messages (type 1). Message 6 is not sent in burst mode.
1063</li>
1064<li>
1065Type 9 message serves the same purpose as Type 1, but does not require a complete satellite set. As a result, Type 9 messages require a more stable clock than a station transmitting Type 1 's, because the satellite corrections have different time references.
1066</li>
1067<li>
1068Type 16 message is simply a text message entered by the user that is transmitted from the base station to the rover. It is used with code-phase differential.
1069</li>
1070<li>
1071Type 18 and 20 messages are RTK uncorrected carrier phase data and carrier phase corrections.
1072</li>
1073<li>
1074Type 19 and 21 messages are the uncorrected pseudo-range measurements and pseudo-range corrections used in RTK.
1075</li>
1076<li>
1077Type 23 message provides the information on the antenna type used on the reference station.
1078</li>
1079<li>
1080Type 24 message carries the coordinates of the installed antenna's ARP in the GNSS coordinate system coordinates.
1081</li>
1082</ul>
1083
1084<p><a name="rtcm3"><h4>8.2.4 RTCM Version 3.x</h4></p>
1085<p>
1086RTCM Version 3.x has been developed as a more efficient alternative to RTCM Version 2.x. Service providers and vendors have asked for a standard that would be more efficient, easy to use, and more easily adaptable to new situations. The main complaint was that the Version 2 parity scheme was wasteful of bandwidth. Another complaint was that the parity is not independent from word to word. Still another was that even with so many bits devoted to parity, the actual integrity of the message was not as high as it should be. Plus, 30-bit words are awkward to handle. The Version 3.x standard is intended to correct these weaknesses.
1087</p>
1088<p>
1089RTCM Version 3.x defines a number of message types. Messages that may be of interest here are:
1090</p>
1091<ul>
1092<li>Type 1001, GPS L1 code and phase.</li>
1093<li>Type 1002, GPS L1 code and phase and ambiguities and carrier to noise ratio.</li>
1094<li>Type 1003, GPS L1 and L2 code and phase.</li>
1095<li>Type 1004, GPS L1 and L2 code and phase and ambiguities and carrier to noise ratio.</li>
1096<li>Type 1005, Station coordinates XZY for antenna reference point.</li>
1097<li>Type 1006, Station coordinates XYZ for antenna reference point and antenna height.</li>
1098<li>Type 1007, Antenna descriptor and ID.</li>
1099<li>Type 1008, Antenna serial number.</li>
1100<li>Type 1009, GLONASS L1 code and phase.</li>
1101<li>Type 1010, GLONASS L1 code and phase and ambiguities and carrier to noise ratio.</li>
1102<li>Type 1011, GLONASS L1 and L2 code and phase.</li>
1103<li>Type 1012, GLONASS L1 and L2 code and phase and ambiguities and carrier to noise ratio.</li>
1104<li>Type 1013, Modified julian date, leap second, configured message types and interval.</li>
1105<li>Type 1014 and 1017, Network RTK (MAK) messages (under development).</li>
1106<li>Type 1019, GPS ephemeris.</li>
1107<li>Type 1020, GLONASS ephemeris.</li>
1108<li>Type 4088 and 4095, Proprietary messages (under development).
1109</li>
1110</ul>
1111
1112<p><a name="rtigs"><h4>8.3. RTIGS</h4></p>
1113<p>
1114RTIGS stands for a data format and transport protocol for GPS observations. It was defined by the Real-Time IGS Working Group (RTIGS WG). Its definition is based on the SOC format. Every RTIGS record has one of the following numbers:
1115</p>
1116<p>
1117Station record number 100<br>
1118Observation record (O_T) number 200<br>
1119Ephemeris record (E_T) number 300<br>
1120Meteorological record (M_T) number 400
1121</p>
1122<p>
1123Every station has one of the following unique numbers:
1124</p>
1125<p>
11261-99 reserved for JPL<br>
1127100-199 reserved for NRCan<br>
1128200-299 reserved for NGS<br>
1129300-399 reserved for ESOC<br>
1130400-499 reserved for GFZ<br>
1131500-599 reserved for BKG<br>
1132600-699 reserved for GEOSCIENCE AUS<br>
1133700-799 others<br>
1134etc
1135</p>
1136<p>
1137The number of bytes in each real time message includes the header as well as the data content, but NOT the pointer.
1138</p>
1139<p>
1140For example:
1141</p>
1142<ul>
1143<li>A station message is output once per hour and is 20 bytes.</li>
1144<li>An observation message is output once per second. The header is 12 bytes long and the SOC data is 21 bytes per PRN. So a typical RTIGSO_T message will be 390 bytes if 8 sats are being tracked.</li>
1145<li>An ephemeris message is output when the ephemeris is decoded by the GPS receiver. The time in the ephemeris header is the collected time. Only one ephemeris can be bundled in a RTIGSE_T message.<br>
1146A RTIGSE_T message contains one eph. The message consists of 12 header bytes and 72 ephemeris bytes, for a total of 84 bytes.</li>
1147<li>The RTIGSM_T (met) message should be issued once every 15 minutes. A basic met message consists of a 12 byte header and 3 longs (temp, press and relative humidity) for a total of 24 bytes.</li>
1148</ul>
1149<p>
1150All records are related to a station configuration indicated by the Issue of Data Station (IODS). The IODS will enable the user to identify the equipment and software that was used to derive the observation data.
1151</p>
1152<p>
1153Each record header contains the GPS Time in seconds which flows continuously from 6 Jan-1980 onwards.
1154</p>
1155<p>
1156The data payload of each record consists of observations. The structures indicate a pointer to data but in fact the broadcast messages do not contain the pointer, only the data. Users will have to manage the data and the pointer is shown in order to illustrate where the data is located in the message and one possible data management option.
1157</p>
1158<p>
1159All record data are in network byte order (Big Endian), i.e. IA32 users have to swap bytes.
1160</p>
1161<p>
1162Visit <u>http://igscb.jpl.nasa.gov/mail/igs-rtwg/2004/msg00001.html</u> for further details.
1163</p>
1164
1165<p><a name="soc"><h4>8.3.1 SOC</h4></p>
1166<p>
1167The SOC format has been designed in July 1999 by the Jet Propulsion Laboratory (JPL) and the California Institute of Technology (CalTech) to transport 1Hz GPS data with minimal bandwidth over the open Internet. SOC follows the 'little-endian' byte order meaning that the low-order byte of a number is stored in memory at the lowest address, and the high-order byte at the highest address. Because the transport layer is UDP, the format does not include sync bits, a checksum, or cyclic redundancy checksum (CRC). SOC allows to transport the GPS observable CA, P1, P2, L1, and L2, efficiently compressed down to 14 bytes with 1 mm range resolution and 0.02 mm phase resolution. SOC contains epochs for cycle slips, a stand-alone time-tag per epoch, a minimum representation of the receiver's clock solution, 3 SNR numbers, a unique site id, a modulo 12 hour sequence number and flags for receiver type and GPS health. SOC's simple structure comprises an 8 byte header, a 9 byte overhead for timetag, number of gps, etc., plus 21 data bytes per gps.
1168</p>
1169<p>
1170Visit <u>http://gipsy.jpl.nasa.gov/igdg/papers/SOC_FORMAT.ppt</u> for further details.
1171</p>
1172<p>
1173</p>
1174<p><a name="config"><h4>8.4. Configuration Example</h4></p>
1175<p>
1176The following table's left column is an example for the contents of a configuration file 'BNC.ini'. It enables the retrieval of stream ACOR0 form www.euref-ip.net for the generation of 15 min RINEX files. RINEX files are uploaded to an archive using script 'up2archive' :
1177</p>
1178<table>
1179<tr></tr>
1180<tr><td><b>Option</b></td><td><b>Affiliation</b></td></tr>
1181<tr><td>[General]</td><td>Settings: Group</td></tr>
1182<tr><td>adviseFail=15</td><td>Outages: Failure threshold</td></tr>
1183<tr><td>adviseReco=5</td><td>Outages: Recovery threshold</td></tr>
1184<tr><td>adviseScript=</td><td>Outages: Script (full path)</td></tr>
1185<tr><td>autoStart=0</td><td>General: Auto start</td></tr>
1186<tr><td>binSample=0</td><td>Feed Engine: Sampling</td></tr>
1187<tr><td>casterUrlList=http://user:pass@euref-ip:2101</td><td>Internal memory: Visited URLs</td></tr>
1188<tr><td>corrIntr=1 day</td><td>Ephemeris Corrections: Interval</td></tr>
1189<tr><td>corrPath=</td><td>Ephemeris Corrections: Directory </td></tr>
1190<tr><td>corrPort=</td><td>Ephemeris Corrections: Port</td></tr>
1191<tr><td>corrTime=5</td><td>Ephemeris Corrections: Wait for full epoch</td></tr>
1192<tr><td>ephIntr=15 min</td><td>RINEX Ephemeris: Interval</td></tr>
1193<tr><td>ephPath=</td><td>RINEX Ephemeris: Directory</td></tr>
1194<tr><td>ephV3=0</td><td>RINEX Ephemeris: Version 3</td></tr>
1195<tr><td>font=</td><td>Internal memory: Used font</td></tr>
1196<tr><td>logFile=/home/weber/bnc.log</td><td>General: Logfile (full path)</td></tr>
1197<tr><td>makePause=0</td><td>Outages: Pause</td></tr>
1198<tr><td>miscMount=</td><td>Miscellaneous: Mountpoint</td></tr>
1199<tr><td>mountPoints=//user:pass@www.euref-ip.net:2101<br>/ACOR0 RTCM_2.3 43.36 351.60 no 1</td><td>Streams: broadcaster:port/mountpoint</td></tr>
1200<tr><td>ntripVersion=1</td><td>Add Streams: NTRIP Version</td></tr>
1201<tr><td>obsRate=</td><td>Outages: Observation rate</td></tr>
1202<tr><td>onTheFlyInterval=1 day</td><td>General: Reread configuration</td></tr>
1203<tr><td>outEphPort=</td><td>RINEX Ephemeris: Port</td></tr>
1204<tr><td>outFile=</td><td>Feed Engine: File (full path)</td></tr>
1205<tr><td>outPort=</td><td>Feed Engine: Port</td></tr>
1206<tr><td>outUPort=</td><td>Feed Engine: Port (unsynchronized)</td></tr>
1207<tr><td>perfIntr=</td><td>Miscellaneous: Log latency</td></tr>
1208<tr><td>proxyHost=</td><td>Proxy: Proxy host</td></tr>
1209<tr><td>proxyPort=</td><td>Proxy: Proxy port</td></tr>
1210<tr><td>rnxAppend=2</td><td>General: Append files</td></tr>
1211<tr><td>rnxIntr=15 min</td><td>RINEX Observations: Interval</td></tr>
1212<tr><td>rnxPath=/home/user/rinex</td><td>RINEX Observations: Directory</td></tr>
1213<tr><td>rnxSample=0</td><td>RINEX Observations: Sampling</td></tr>
1214<tr><td>rnxScript=/home/user/rinex/up2archive</td><td>RINEX Observations: Script (full path)</td></tr>
1215<tr><td>rnxSkel=</td><td>RINEX Observations: Skeleton extension</td></tr>
1216<tr><td>rnxV3=0</td><td>RINEX Observation: Version 3</td></tr>
1217<tr><td>scanRTCM=0</td><td>Miscellaneous: Scan RTCM</td></tr>
1218<tr><td>serialAutoNMEA=0</td><td>Serial Link: Auto NMEA</td></tr>
1219<tr><td>serialBaudRate=9600</td><td>Serial Link: Baud rate</td></tr>
1220<tr><td>serialDataBits=8</td><td>Serial Link: Data bits</td></tr>
1221<tr><td>serialMountPoint=</td><td>Serial Link: Mountpoint</td></tr>
1222<tr><td>serialParity=NONE</td><td>Serial Link: Parity</td></tr>
1223<tr><td>serialPortName=</td><td>Serial Link: Port name</td></tr>
1224<tr><td>serialStopBits=1</td><td>Serial Link: Stop bits</td></tr>
1225<tr><td>startTab=0</td><td>Internal memory: Top tab</td></tr>
1226<tr><td>waitTime=5</td><td>Feed Engine: Wait for full epoch</td></tr>
1227</table>
1228</p>
1229<p>
1230Note that the following configuration options saved on disk can be changed/edited on-the-fly while BNC is already processing data:
1231</p>
1232<p>
1233<ul>
1234<li>'mountPoints' to change the selection of streams to be processed, see section 'Streams',</li>
1235<li>'waitTime' to change the 'Wait for full epoch' option, see section 'Feed Engine', and</li>
1236<li>'binSampl' to change the 'Sampling' option, see section 'Feed Engine'.</li>
1237</ul>
1238</p>
1239
1240<p><a name="links"><h3>8.5 Links</h3></p>
1241<table>
1242<tr></tr>
1243<tr><td>NTRIP &nbsp;</td><td><u>http://igs.bkg.bund.de/index_ntrip.htm</u></td></tr>
1244<tr><td>EUREF-IP NTRIP broadcaster &nbsp;</td><td><u>http://www.euref-ip.net/home</u></td></tr>
1245<tr><td>IGS-IP NTRIP broadcaster &nbsp;</td><td><u>http://www.igs-ip.net/home</u></td></tr>
1246<tr><td>NTRIP broadcaster overview &nbsp;</td><td><u>http://www.rtcm-ntrip.org/home</u></td></tr>
1247<tr><td>EUREF-IP Project &nbsp;</td><td><u>http://www.epncb.oma.be/euref_IP</u></td></tr>
1248<tr><td>Real-time IGS Pilot Project &nbsp;</td><td><u>http://www.rtigs.net/pilot</u></td></tr>
1249<tr><td>Radio Technical Commission<br>for Maritime Services &nbsp;</td><td><u>http://www.rtcm.org</u>
1250</table>
1251
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