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1<h3>BKG Ntrip State Space Server (BNS) Version 1.0</h3>
2
3<p>
4The BKG Ntrip State Space Server (BNS) is a program for transforming GNSS satellite clocks and orbits into corrections to Broadcast Ephemeris. These corrections are then encode in a (premature) RTCM Version 3.x format and uploaded to NTRIP broadcasters like <u>http://www.euref-ip.net/home</u> or <u>http://www.igs-ip.net/home.</u> BNS is created as a tool for service providers with real-time access to a network of continentally or globally distributed GNSS reference stations.
5</p>
6
7<p>
8BNS 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 PP).
9</p>
10
11<p>
12BNS is released under the GNU General Public License (GPL). Binaries for BNS are available for Windows, 32-bit and 64-bit Linux (compiled under -m32 32-bit compatibility mode), Solaris, and Mac OS X systems. The MinGW compiler (Version 5.3.1) is used to produce the Windows binary. It is likely that BNS can be compiled on other systems where a GNU compiler and Qt Version 4.3.2 are available.
13</p>
14
15<p>
16Before running, please ensure that you have installed the latest version available. This can be obtained from <u>http://igs.bkg.bund.de/index_ntrip_down.htm</u>. We are continuously working on the program and would appreciate any comments, suggestions, or bug reports. They can be emailed 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=#function>2. Functioning</a><br>
24<a href=#resources>3. Resources</a><br>
25<a href=#options>4. Options</a><br>
26<a href=#limits>5. Limitations</a><br>
27<a href=#authors>6. Authors</a><br>
28<a href=#annex>7. Annex</a><br>
29</h4>
30</p>
31
32<p><a name="purpose"><h3>1. Purpose</h3></p>
33<p>
34Differential GNSS and RTK operation using RTCM streams is currently based on corrections and/or raw measurements from single or multiple reference stations. This approach to differential positioning is using 'observation space' information. The representation with the RTCM standard can be called 'Observation Space Representation' (OSR).
35</p>
36<p>
37An alternative to the observation space approach is the so called 'sate space' approach. The principle here is to provide information on individual error sources and can be called 'State Space Representation' (SSR). For a rover position, state space information concerning precise satellite clocks, orbits, ionosphere, troposphere et cetera can be converted into observation space and used to correct the rover observables for more accurate positioning. Alternatively the state information can directly be used in the rover's processing or adjustment model.
38</p>
39
40<p>In order to support applications following the state space approach, the purpose of BNS is to
41
42<ul>
43<li>read GNSS clocks and orbits in SP3 format from an IP port. They can be produced by a real-time GNSS engine such as RTNet and should be referenced to the IGS Earth-Centered-Earth-Fixed (ECEF) reference system.</li>
44<li>read GNSS Broadcast Ephemeris in RINEX Navigation format from an IP port. This information can be provided in real-time by the 'BKG Ntrip Client' (BNC) program.</li>
45<li>convert the IGS Earth-Centered-Earth-Fixed clocks and and orbits into corrections to Broadcast Ephemeris with radial, along-track and cross-track components.</li>
46<li>refer the clock and orbit corretions to a specific reference system.</li>
47<li>upload the clock and orbit corrections as an RTCM Version 3.x stream to an NTRIP Broadcaster.</li>
48<li>log the Broadcast Ephemeris clock corrections as files in Clock RINEX files.</li>
49<li>log the Broadcast Ephemeris orbit corrections as files in SP3 files.</li>
50</ul>
51</p>
52<p>
53Note that BNS currently only generates premature RTCM Version 3.x message types 4056 for combined GPS orbit and clock corrections and 4057 for combined GLONASS orbit and clock corrections to Broadcast Ephemeris.
54</p>
55
56<p><a name="function"><h3>2. Functioning</h3></p>
57<p>
58The procedures taken by BNS to generate clock and orbit corrections to Broadcast Ephemeris in radial, along-track and cross-track components are as follow:
59</p>
60<p>
61<ul>
62<li>Continuously receive up-to-date Broadcast Ephemeris carrying approximate orbits and clocks for all satellites. Receive them in RINEX Version 3 Navigation file format. Read new Broadcast Ephemeris immediately whenever they become available. Tools like the 'BKG Ntrip Client' (BNC) provide this information.</li>
63</ul>
64</p>
65<p>
66Then, epoch by epoch:
67<ul>
68<li>Continuously receive the best available clock and orbit estimates for all satellites in X,Y,Z Earth-Centered-Earth-Fixed IGS05 reference system. Receive them every epoch in SP3 format as provided by a real-time GNSS engine such as RTNet.</li>
69<li>Calculate X,Y,Z coordinates from Broadcast Ephemeris orbits.</li>
70<li>Calculate differences dX,dY,dZ between Broadcast Ephemeris and IGS05 orbits.</li>
71<li>Tranform these differences into radial, along-track and cross-track corrections to Broadcast Ephemeris orbits.</li>
72<li>Calculate corrections to Broadcast Ephemeris clocks as differences between Broadcast Ephemeris and IGS05 clocks.</li>
73<li>Encode Broadcast Ephemeris clock and orbit corrections in RTCM Version 3.x format.</li>
74<li>Upload corrections stream to NTRIP Broadcaster.</li>
75</ul>
76</p>
77<p>
78Although it is not compulsory, because BNS puts a significant load on the communication link, it is recommended that BNS, the Broadcast Ephemeris server (i.e. BNC), and the server providing orbits and clocks (i.e. RTNet) are run on the same host.
79</p>
80
81<p><a name="resources"><h3>3. Resources</h3></p>
82<p>
83The current size of the real-time stream produced by BNS is in the order of 5 kbits/sec depending on the number of visible satellites. When uploading the stream to an NTRIP Broadcaster, user needs to ensure that the connection used can sustain the required bandwidth.
84</p>
85<p>
86Running BNS requires the clock of the host computer to be properly synchronized.
87</p>
88
89<p><a name="options"><h3>4. Options</h3></p>
90
91<p>
92All options for running BNS on Unix/Linux/Mac systems are saved in file ${HOME}/.config/BKG/BKG_NTRIP_Server.conf, see annexed 'Configuration File' example. On Windows systems options are saved in register BKG_NTRIP_Server. The self-explaining contents of the configuration file or the Windows register can easily be edited.
93</p>
94
95<p>
964.1. <a href=#file>File</a><br>
974.2. <a href=#help>Help</a><br>
984.3. <a href=#proxy>Proxy</a><br>
994.4. <a href=#general>General</a><br>
100&nbsp; &nbsp; &nbsp; 4.4.1. <a href=#logfile>Logfile</a><br>
101&nbsp; &nbsp; &nbsp; 4.4.2. <a href=#appfile>Append Files</a><br>
1024.5. <a href=#eph>RINEX Ephemeris</a><br>
103&nbsp; &nbsp; &nbsp; 4.5.1. <a href=#ephserver>Host & Port</a><br>
104&nbsp; &nbsp; &nbsp; 4.5.2. <a href=#ephsave>Save</a><br>
1054.6. <a href=#co>Clocks & Orbits</a><br>
106&nbsp; &nbsp; &nbsp; 4.6.1. <a href=#coport>Listening Port</a><br>
107&nbsp; &nbsp; &nbsp; 4.6.2. <a href=#cosave>Save</a><br>
1084.7. <a href=#ephc>Ephemeris Corrections</a><br>
109&nbsp; &nbsp; &nbsp; 4.7.1. <a href=#ephcserver>Host & Port, Password</a><br>
110&nbsp; &nbsp; &nbsp; 4.7.2. <a href=#ephcmount>Mountpoint</a><br>
111&nbsp; &nbsp; &nbsp; 4.7.3. <a href=#ephcsys>System</a><br>
112&nbsp; &nbsp; &nbsp; 4.7.4. <a href=#ephcsave>Save</a><br>
1134.8. <a href=#clkrnx>RINEX Clocks</a><br>
114&nbsp; &nbsp; &nbsp; 4.8.1. <a href=#clkdir>Directory</a><br>
115&nbsp; &nbsp; &nbsp; 4.8.2. <a href=#clkint>Interval & Sampling</a><br>
1164.9. <a href=#orb>SP3 Orbits</a><br>
117&nbsp; &nbsp; &nbsp; 4.9.1. <a href=#orbdir>Directory</a><br>
118&nbsp; &nbsp; &nbsp; 4.9.2. <a href=#orbint>Interval & Sampling</a><br>
1194.10. <a href=#start>Start</a><br>
1204.11. <a href=#stop>Stop</a><br>
1214.12. <a href=#nw>No Window</a>
122</p>
123
124<p><a name="file"><h4>4.1. File</h4></p>
125
126<p>
127The 'File' button lets you
128<ul>
129<li>
130select an appropriate font.<br>
131Use smaller font size if the BNS main window extends beyond the size of your screen.
132</li>
133<li> save selected options.<br>
134Note that on Windows systems options are saved in register BKG_NTRIP_Server. On Unix/Linux/Mac systems options are saved in file ${HOME}/.config/BKG/BKG_NTRIP_Server.conf.
135</li>
136<li>
137quit the BNS program.
138</li>
139</ul>
140</p>
141
142<p><a name="help"><h4>4.2. Help</h4></p>
143
144<p>
145The 'Help' button provides access to
146<ul>
147<li>
148help contents.<br>
149You may keep the 'Help Contents' window open while configuring BNS.
150</li>
151<li>
152a 'Flow Chart' showing BNS linked to tools like BNC and a real-time GNSS engine such as RTNet.
153</li>
154<li>
155general information about BNS.<br>
156Close the 'About BNS' window to continue working with BNS.
157</li>
158</ul>
159</p>
160<p>
161BNS 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 will appear immediately; it disappears as soon as the focus is shifted to 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.
162</p>
163
164<p><a name="proxy"><h4>4.3. Proxy - for usage in a protected LAN</h4></p>
165
166<p>
167If you are running BNS 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 address and port of your proxy server, check the proxy server settings in your Internet browser or ask your network administrator.
168</p>
169<p>
170Note 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 Casters. If these are not possible, you might need to run BNS outside your LAN on a host that has unobstructed connection to the Internet.
171</p>
172<p><a name="general"><h4>4.4. General Options</h4></p>
173
174<p><a name="logfile"><h4>4.4.1 Logfile - optional</h4></p>
175<p>
176Records of BNC's activities are shown in the Log section on the bottom of the main window. These logs can be saved into a file when a valid path is specified in the 'Log (full path)' field. The message log covers 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 'Log (full path)' is an empty option field, meaning that BNC logs will not saved into a file.
177</p>
178
179<p><a name="appfile"><h4>4.4.2 Append Files</h4></p>
180<p>
181When BNS 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 BNS, a system crash or when BNS had 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 BNS.
182</p>
183
184<p><a name="eph"><h4>4.5. RINEX Ephemeris</h4></p>
185<p>
186BNS requires GNSS Broadcast Ephemeris in RINEX Version 3 Navigation file format from an IP address and port. This information can be provided in real-time by the 'BKG Ntrip Client' (BNC) program. Note that whenever a new set of Broadcast Ephemeris becomes available, BNS needs it immediately.
187</p>
188
189<p>
190The following is an example log of Broadcast Ephemeris records in RINEX Version 3 Navigation file format for satellite GPS PRN32 and GLONASS PRN04:
191</p>
192
193<p>
194<pre>
195G32 2008 07 22 12 00 00 3.08818183839e-04 2.72848410532e-12 0.00000000000e+00
196 1.10000000000e+01 -4.00312500000e+01 4.63269297026e-09 9.74027926504e-01
197 -2.19419598579e-06 1.39143558918e-02 8.25151801109e-06 5.15381674576e+03
198 2.16000000000e+05 -8.56816768646e-08 -3.26801342873e-02 -2.94297933578e-07
199 9.68688494953e-01 2.30468750000e+02 -1.30607654294e+00 -8.26105839196e-09
200 -3.62872257943e-10 1.00000000000e+00 1.48900000000e+03 0.00000000000e+00
201 2.00000000000e+00 0.00000000000e+00 -2.79396772385e-09 1.10000000000e+01
202 0.00000000000e+00 0.00000000000e+00
203R04 2008 07 22 08 15 14 4.76110726595e-05 0.00000000000e+00 2.88600000000e+04
204 -1.76267827148e+04 -4.64202880859e-01 1.86264514923e-09 0.00000000000e+00
205 -1.79631489258e+04 -3.41343879700e-01 -2.79396772385e-09 6.00000000000e+00
206 -4.20270556641e+03 3.50097942352e+00 0.00000000000e+00 0.00000000000e+00
207</pre>
208</p>
209
210<p><a name="ephserver"><h4>4.5.1 Host & Port - mandatory</h4></p>
211<p>
212Enter the IP address and port number of a Broadcast Ephemeris server like BNC to establish a persistent socket connection, see section 'Flow Chart' under 'Help' for socket communication details. If BNS runs on the same host as BNC, 127.0.0.1 should be used as the server's IP address. Make sure that this server is up and running before you start BNS.
213</p>
214
215<p><a name="ephsave"><h4>4.5.2 Save - optional</h4></p>
216</p>
217Specify the full path to a file where received Broadcast Ephemeris will be logged. Beware that the size of this file can rapidly increase. Default is an empty option field meaning that logging is disabled.
218</p>
219
220<p><a name="co"><h4>4.6. Clocks & Orbits</h4></p>
221<p>
222BNS requires GNSS clocks and orbits in the IGS Earth-Centered-Earth-Fixed (ECEF) reference system in SP3 format. They can be provided by a real-time GNSS engine such as RTNet. Their sampling rate should not be much greater than 10 sec. Note that otherwise in IP streaming involved tools on the NTRIP Broadcaster or client side may respond with a timeout.
223</p>
224
225<p>
226Below you find an example of precise clocks and orbits coming in SP3 format from a real-time GNSS engine. Each epoch starts with an asterisk character followed by GPS Week, Second in GPS Week and Number of satellites. Subsequent records provide the following set of parameters for each satellite:
227</p>
228
229<p>
230<ul>
231<li>GNSS Indicator and Satellite Vehicle Pseudo Random Number</li>
232<li>X,Y,Z coordinates in Earth-Centered-Earth-Fixed system [km]</li>
233<li>Satellite clock error [microsecond]</li>
234</ul>
235</p>
236
237</p>
238<p>
239<pre>
240* 2008 11 15 23 9 40.00000000
241PG02 9913.526202 -14009.502013 20043.508402 172.954389
242PG04 23093.835904 -6682.421653 11570.857634 -233.598390
243PG07 24249.710621 7319.754680 8146.397178 23.216940
244PG08 26390.024445 40.546316 -4908.638575 -178.106488
245PG10 1835.245663 -21440.492626 15205.319419 -7.272325
246PG13 12906.569448 6704.608105 22108.581216 277.382794
247PG16 -6605.961090 17147.164247 19156.319313 95.078459
248PG20 13676.316680 22650.428992 2457.051428 98.981972
249PG23 6709.764296 15204.810711 20604.601368 380.096453
250PG25 19695.705366 9866.220333 15065.609012 26.781926
251PG27 25598.219004 4571.609372 6357.551439 0.304345
252PG29 -12376.531693 -8988.235685 21818.571434 -29.839454
253PR04 9918.187580 23513.478040 319.847487 151.558351
254PR06 8858.433630 -7341.610546 22646.535467 -244.283462
255PR07 -2285.074648 -21548.431780 13471.401525 -122.300100
256PR14 -4723.060343 10040.375495 22946.780676 -113.677871
257PR15 14469.798068 10358.339867 18230.729298 79.645569
258PR20 17648.744681 -16698.956975 -7876.252525 -62.588294
259PR21 10448.514425 -21096.368284 9681.207096 -122.789091
260PR22 -2707.192952 -13243.085608 21689.194398 -170.976408
261PR23 -14575.573714 2817.925995 20728.130339 -263.187906
262</pre>
263</p>
264
265<p><a name="coport"><h4>4.6.1 Listening Port - mandatory</h4></p>
266<p>
267BNS is listening at an IP port for incoming GNSS clocks and orbits in SP3 format. Enter the respective IP port number to setup a server socket for incoming data, see section 'Flow Chart' under 'Help' for socket communication details. Make sure that the software providing clocks and orbits is up and running before you start BNS.
268</p>
269
270<p><a name="cosave"><h4>4.6.2 Save - optional</h4></p>
271<p>
272Specify the full path to a file where received clocks and orbits from a real-time engine will be logged. Beware that the size of this file can rapidly increase. Default is an empty option field meaning that logging is disabled.
273</p>
274
275<p><a name="ephc"><h4>4.7. Ephemeris Corrections</h4></p>
276<p>
277BNS can upload the resulting stream(s) of clock and orbit corrections to Broadcast Ephemeris to an NTRIP Broadcaster. Both EUREF and IGS operate an NTRIP broadcaster at <u>http://www.euref-ip.net/home</u> and <u>http://www.igs-ip.net/home</u> which can be used for stream upload. The stream's format is RTCM Version 3.x. Note that it only carries the thentative message Types 4056 and 4057 for combined orbit and clock corrections to GPS and GLONASS Broadcast Ephemeris.
278</p>
279
280<p><a name="ephcserver"><h4>4.7.1 Host & Port, Password - optional</h4></p>
281<p>
282Enter the NTRIP Caster's 'Host' IP name or number for stream upload.
283</p>
284<p>
285Enter the NTRIP Caster's IP 'Port' number for stream upload. Note that NTRIP Casters are often configured to provide access on more than one port, usually port 80 and 2101. If you experience communication problems on port 80, you should try to use the alternative port(s).
286</p>
287</p>
288In NTRIP Version 1.0 stream upload may be protected through an upload 'Password'. Enter the password you received from the Caster operator along with the mountpoint(s).
289</p>
290
291<p><a name="ephcmount"><h4>4.7.2 Mountpoint - mandatory if 'Host' is set</h4></p>
292<p>
293Each stream on an NTRIP Caster is defined using a unique source ID called mountpoint. An NTRIP Server like BNS upload a stream to the Caster by referring to a dedicated mountpoint that has been set by the Caster operator. Specify here the mountpoint based on the detail you received from the operator for your stream. It is often a four character ID (capital letters) plus an integer number.
294<p>
295
296<p><a name="ephcsys"><h4>4.7.3 System - mandatory if 'Host' is set</h4></p>
297<p>
298BNS refers its final clock and orbit corrections to a specific reference system. Available options are
299<p>
300<ul>
301<li>IGS05 which stands for the GNSS-based IGS realization of the International Terrestrial Reference Frame (ITRF2005), and</li>
302<li>ETRS89 which stands for the European Terrestrial Reference System 1989 adopted by EUREF.</li>
303</ul>
304</p>
305
306<p>
307<u>IGS05:</u>
308As the clocks and orbits coming from real-time GNSS engine are expected to be in the IGS05 system, no transformation is carried out if this option is selected.
309</p>
310<p>
311<u>ETRS89:</u>
312From the complete transformation chain 'IGS05->ITRF2005->ITRF2000->ETRS89' only the transformation 'ITRF2000->ETRS89' has been implemented. The formulas for that are taken from 'Boucher and Altamimi 2007: Specifications for reference frame fixing in the analysis of EUREF GPS campaign', see <u>http://etrs89.ensg.ign.fr/memo2007.pdf</u>. The following 6 Helmert transformation parameters were introduced:
313</p>
314<p>
315<pre>
316Translation in X: 0.054 m
317Translation in Y: 0.051 m
318Translation in Z: -0.048 m
319Rotation rate in X: 0.081 mas/y
320Rotation rate in Y: 0.490 mas/y
321Rotation rate in Z: -0.792 mas/y
322T0: 1989
323</pre>
324</p>
325<p>
326Note that the neglect of transformations 'IGS05->ITRF2005->ITRF2000' in BNS may cause discrepancies up to a maximum of 2 centimenters.
327<p>
328
329
330<p><a name="ephcsave"><h4>4.7.4 Save - optional</h4></p>
331<p>
332The clock and orbit corrections streamed by BNS to the NTRIP Caster can be logged locally. Specify a full 'Save stream' path here to save this information to a local file. Default value for 'Save stream' is an empty option field, meaning that logging is disabled.
333</p>
334<p>
335The file is in plain ASCII format comprising records containing the following set of parameters:
336</p>
337
338<p>
339<ul>
340<li>GPS Week</li>
341<li>Second in GPS Week</li>
342<li>GNSS Indicator and Satellite Vehicle Pseudo Random Number</li>
343<li>IOD referring to Broadcast Ephemeris set</li>
344<li>Clock Correction to Broadcast Ephemeris [m]</li>
345<li>Radial Component of Orbit Correction to Broadcast Ephemeris [m]</li>
346<li>Along-track Component of Orbit Correction to Broadcast Ephemeris [m]</li>
347<li>Cross-track Component of Orbit Correction to Broadcast Ephemeris [m]</li>
348</ul>
349</p>
350<p>
351The following is an example file contents based on combined orbit and clock corrections for GPS and GLONASS carried in RTCM Version 3.x message Type 4056 and 4057:
352</p>
353<p>
354<pre>
3551489 325606.0 G31 18 -1.021 0.110 -1.308 -0.120
3561489 412006.0 R10 18 7.342 1.393 4.858 -2.634
3571489 412006.0 R19 18 4.696 2.358 1.707 -2.907
358...
3591489 325607.0 G30 80 6.022 0.591 -0.318 0.022
3601489 325607.0 G31 18 -1.022 0.110 -1.308 -0.120
3611489 412007.0 R10 18 7.341 1.390 4.860 -2.636
3621489 412007.0 R19 18 4.698 2.356 1.706 -2.906
363...
364</pre>
365</p>
366
367<p><a name="clkrnx"><h4>4.8. RINEX Clocks</h4></p>
368<p>
369The clock corrections generated by BNS can be logged separately in Clock RINEX format. The file naming follows the RINEX convention.
370</p>
371
372<p><a name="clkdir"><h4>4.8.1 Directory - optional</h4></p>
373<p>
374Here you can specify the path to where the Clock RINEX files will be stored. If the specified directory does not exist, BNS will not create Clock RINEX files. Default value for 'Directory' is an empty option field, meaning that logging of Clock RINEX files is disabled.
375</p>
376
377<p><a name="clkint"><h4>4.8.2 Interval & Sampling - mandatory if 'Directory' is set</h4></p>
378<p>
379Select the length of the Clock RINEX file generated. The default value is 1 day.
380</p>
381
382<p>
383Select the Clock RINEX sampling interval in seconds. A value of zero '0' tells BNS to store all received epochs into Clock RINEX. This is the default value.
384</p>
385
386<p><a name="orb"><h4>4.9. SP3 Orbits</h4></p>
387<p>
388The orbit corrections generated by BNS can be logged separately in SP3 Orbit files. The file naming follows the IGS convention.
389</p>
390
391<p><a name="orbdir"><h4>4.9.1 Directory - optional</h4></p>
392<p>
393Here you can specify the path to where the SP3 Orbit files will be stored. If the specified directory does not exist, BNS will not create SP3 Orbit files. Default value for 'Directory' is an empty option field, meaning that logging of SP3 Orbit files is disabled.
394</p>
395
396<p><a name="orbint"><h4>4.9.2 Interval & Sampling - mandatory if 'Directory' is set</h4></p>
397<p>
398Select the length of the SP3 Orbit file generated. The default value is 1 day.
399</p>
400<p>
401Select the SP3 Orbit file sampling interval in seconds. A value of zero '0' tells BNS to store all received epochs into SP3 Orbit files. This is the default value.
402</p>
403
404<p><a name="start"><h4>4.10. Start</h4></p>
405<p>
406Hit 'Start' to start receiving IGS orbits and clocks and convert them into corrections to Broadcast Ephemeris. Note that when started BNS by default will begin with new files which might overwrite existing files when necessary unless the option 'Append files' is ticked.
407</p>
408
409<p><a name="stop"><h4>4.11. Stop</h4></p>
410<p>
411Hit the 'Stop' button in order to stop BNS.
412</p>
413
414<p><a name="nw"><h4>4.12. No Window - optional</h4></p>
415<p>
416On all systems BNS can be started in batch mode with the command line option '-nw'. BNS will then run in 'no window' mode, using options from the configuration file ${HOME}/.config/BKG/BNC_NTRIP_Server.conf (Unix/Linux/Mac, see 'Configuration File' example in the Annex) or from the register BKG_NTRIP_Server (Windows).
417</p>
418<p>
419The self-explanatory contents of the configuration file or the Windows registry can easily be edited. Before editing, terminate BNS first using Windows Task Manager when running it in 'no window' mode on Windows systems.
420</p>
421<p><a name="limits"><h3>5. Limitations</h3></p>
422<ul>
423<li>
424In Qt-based desktop environments (such as KDE) on Unix/Linux/Mac platforms users may experience a crash at startup even when BNS is run 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 BNS. Entering the command 'unset SESSION_MANAGER' before running BNS may help as a work-around.
425</li>
426<li>
427Currently BNS can only generate premature RTCM Version 3.x message Type 4056 and 4057 for combined GPS and GLONASS orbit and clock corrections. Note that the length of data fields in these messages is not yet standardized. What's implemented in BNS is just a temporary solution.
428</li>
429<li>
430We experienced some limitation with the Standard Version of Microsoft Windows related to socket communication where sockets are not always handled properly. Since BNS makes intensive use of communication through sockets, we recommend to use the Server Version of Microsoft Windows when running BNS continuously for extended period on a Windows platform.
431</li>
432<li>
433Once BNS has been started, its configuration can not be changed unless without a restart. An on-the-fly reconfiguration is not implemented.
434</li>
435<br>
436</ul>
437<p><a name="authors"><h3>6. Authors</h3></p>
438<p>
439The BKG Ntrip State Space Server (BNS) 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. BNS includes a GNU GPL open source RTCM 3.x encoder, written for BKG by Dirk Stoecker, Alberding GmbH, Schoenefeld.
440</p>
441<p>
442Georg Weber<br>
443Federal Agency for Cartography and Geodesy (BKG)<br>
444Frankfurt, Germany<br>
445[euref-ip@bkg.bund.de] or [igs-ip@bkg.bund.de]
446</p>
447
448<p><a name="annex"><h3>7. Annex</h3></p>
449<p>
4507.1. <a href=#history>History</a><br>
4517.2. <a href=#rtcm>RTCM</a><br>
452&nbsp; &nbsp; &nbsp; 7.2.1 RTCM <a href=#ntrip>NTRIP</a><br>
453&nbsp; &nbsp; &nbsp; 7.2.2 RTCM <a href=#rtcm3>Version 3.x</a><br>
4547.3. <a href=#config>Configuration File</a><br>
4557.4. <a href=#links>Links</a><br>
456</p>
457
458<p><a name=history><h4>7.1 History</h4></p>
459</p>
460<table>
461<tr></tr>
462<tr><td>Nov 2008 &nbsp;</td><td>Version 1.0 &nbsp;</td><td>[Add] Source code and binaries published.</td></tr>
463</table>
464</p>
465
466<p><a name="rtcm"><h4>7.2. RTCM</h4></p>
467
468<p>
469The 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.
470</p>
471<p>
472Personal copies of RTCM Recommended Standards can be ordered through <u>http://www.rtcm.org/orderinfo.php</u>.
473</p>
474
475<p><a name="ntrip"><h4>7.2.1 NTRIP</h4></p>
476
477<p>
478'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.
479</p>
480
481<p>
482NTRIP 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.
483</p>
484
485<p>
486NTRIP 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. The 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.
487</p>
488
489<p>
490NTRIP is an open none-proprietary protocol. Major characteristics of NTRIP's dissemination technique are:
491<ul>
492<li>Based on the popular HTTP streaming standard; comparatively easy to implement when having limited client and server platform resources available.</li>
493<li>Application not limited to one particular plain or coded stream content; ability to distribute any kind of GNSS data.</li>
494<li>Potential to support mass usage; disseminating hundreds of streams simultaneously for thousands of users possible when applying modified Internet Radio broadcasting software.</li>
495<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>
496<li>Enables streaming over mobile IP networks because of using TCP/IP.</li>
497</ul>
498</p>
499
500<p><a name="rtcm3"><h4>7.2.2 RTCM Version 3.x</h4></p>
501<p>
502RTCM Version 3.x has been developed as a better alternative to RTCM Version 2.x. Service providers and vendors have asked for a standard that would be efficient, easy to use, and easily adaptable to new situations.
503</p>
504RTCM is in the process of developing new Version 3 message types to carry satellite clock and orbit corrections in real-time. Based on the latest available proposal, the following premature messages currently under discussion of relevance to BNS are listed here:
505<p>
506<ul>
507<li>Message type 4050: GPS orbit corrections to Broadcast Ephemeris</li>
508<li>Message type 4051: GPS clock corrections to Broadcast Ephemeris</li>
509<li>Message type 4052: GPS code biases</li>
510<li>Message type 4053: GLONASS orbit corrections to Broadcast Ephemeris</li>
511<li>Message type 4054: GLONASS clock corrections to Broadcast Ephemeris</li>
512<li>Message type 4055: GLONASS code biases</li>
513<li>Message type 4056: Combined orbit and clock corrections to GPS Broadcast Ephemeris</li>
514<li>Message type 4057: Combined orbit and clock corrections to GLONASS Broadcast Ephemeris</li>
515</ul>
516</p>
517<p>
518RTCM Version 3.x streams carrying these messages may be used for example to support real-time Precise Point Positioning (PPP) applications using the 'state space' approach.
519</p>
520
521<p><a name="config"><h4>7.3. Configuration File</h4></p>
522<p>
523The following is an example of the contents of a Unix/Linux/Mac configuration file ${HOME}/.config/BKG/BKG_NTRIP_Server.conf. It enables the upload of streams CLCK1 and CLCK2 to www.igs-ip.net. Clock RINEX files and SP3 Orbit files are saved to a directory /home/weber/rinex :
524</p>
525<p>
526<pre>
527[General]
528clkPort=7000
529ephEcho=/home/weber/rinex/eph.rnx
530ephHost=clock-ip.bkg.bund.de
531ephPort=6000
532fileAppend=0
533font="Helvetica [Adobe],8,-1,5,75,0,0,0,0,0"
534inpEcho=/home/weber/rinex/ClocksOrbits.dat
535logFile=/home/weber/rinex/bns.log
536mountpoint_1=CLCK1
537mountpoint_2=CLCK2
538outFile_1=/home/weber/rinex/CLCK1
539outFile_2=/home/weber/rinex/CLCK2
540outHost=www.igs-ip.net
541outPort=2101
542password=serverPass
543proxyHost=
544proxyPort=
545refSys_1=IGS05
546refSys_2=ETRS89
547rnxIntr=1 day
548rnxPath=/home/weber/rinex
549rnxSampl=30
550sp3Intr=1 day
551sp3Path=/home/weber/rinex
552sp3Sampl=300
553</pre>
554</p>
555
556<p>
557Note that on Windows systems configuration options are saved in register BKG_NTRIP_Server.
558</p>
559
560<p><a name="links"><h4>7.4 Links</h4></p>
561<table>
562<tr></tr>
563<tr><td>NTRIP &nbsp;</td><td><u>http://igs.bkg.bund.de/index_ntrip.htm</u></td></tr>
564<tr><td>EUREF-IP NTRIP broadcaster &nbsp;</td><td><u>http://www.euref-ip.net/home</u></td></tr>
565<tr><td>IGS-IP NTRIP broadcaster &nbsp;</td><td><u>http://www.igs-ip.net/home</u></td></tr>
566<tr><td>NTRIP broadcaster overview &nbsp;</td><td><u>http://www.rtcm-ntrip.org/home</u></td></tr>
567<tr><td>EUREF-IP Project &nbsp;</td><td><u>http://www.epncb.oma.be/euref_IP</u></td></tr>
568<tr><td>Real-time IGS Pilot Project &nbsp;</td><td><u>http://www.rtigs.net/pilot</u></td></tr>
569<tr><td>Radio Technical Commission<br>for Maritime Services &nbsp;</td><td><u>http://www.rtcm.org</u>
570</table>
571
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