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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 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. The latest version of BNS 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 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 plain ASCII 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 file 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>upload the clock and orbit corrections as a stream to an NTRIP Broadcaster.</li>
47<li>log the Broadcast Ephemeris clock corrections as files in Clock RINEX files.</li>
48<li>log the Broadcast Ephemeris orbit corrections as files in SP3 files.</li>
49</ul>
50</p>
51<p>
52Note that BNS currently only generates the tentative RTCM Version 3.x message types 4056 for Combined GPS and GLONASS orbit corrections and 4057 for Combined GPS and GLONASS clock corrections to Broadcast Ephemeris.
53</p>
54
55<p><a name="function"><h3>2. Functioning</h3></p>
56<p>
57The procedures taken by BNS to generate clock and orbit corrections to Broadcast Ephemeris in radial, along-track and cross-track components are as follow:
58</p>
59<p>
60<ul>
61<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>
62</ul>
63</p>
64<p>
65Then, epoch by epoch:
66<ul>
67<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 a plain ASCII format as provided by a real-time GNSS engine such as RTNet.</li>
68<li>Calculate X,Y,Z coordinates from Broadcast Ephemeris orbits.</li>
69<li>Calculate differences dX,dY,dZ between Broadcast Ephemeris orbits and IGS05 orbits.</li>
70<li>Model orbit differences through low degree polynomial.</li>
71<li>Derive model-based estimation of corrections to Broadcast Ephemeris orbits.
72<li>Tranform model-based orbit corrections into radial, along-track and cross-track components.</li>
73<li>Calculate differences dC between clocks from Broadcast Ephemeris and IGS05 clocks.</li>
74<li>Model clock differences through low degree polynomial.</li>
75<li>Derive model-based estimation of corrections to Broadcast Ephemeris clocks.</li>
76<li>Encode Broadcast Ephemeris clock and orbit corrections in RTCM Version 3.x format.</li>
77<li>Upload corrections in RTCM Verion 3 format to NTRIP Broadcaster.</li>
78</ul>
79</p>
80<p>
81Although 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.
82</p>
83
84<p><a name="resources"><h3>3. Resources</h3></p>
85<p>
86The size of the real-time stream produced by BNS is in the order 2 to 3 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.
87</p>
88<p>
89Running BNS requires the clock of the host computer to be properly synchronized.
90</p>
91
92<p><a name="options"><h3>4. Options</h3></p>
93<p>
944.1. <a href=#file>File</a><br>
954.2. <a href=#help>Help</a><br>
964.3. <a href=#proxy>Proxy</a><br>
974.4. <a href=#general>General</a><br>
98&nbsp; &nbsp; &nbsp; 4.4.1. <a href=#logfile>Logfile</a><br>
99&nbsp; &nbsp; &nbsp; 4.4.2. <a href=#appfile>Append Files</a><br>
1004.5. <a href=#eph>RINEX Ephemeris</a><br>
101&nbsp; &nbsp; &nbsp; 4.5.1. <a href=#ephserver>Host & Port</a><br>
102&nbsp; &nbsp; &nbsp; 4.5.2. <a href=#ephsave>Save</a><br>
1034.6. <a href=#co>Clocks & Orbits</a><br>
104&nbsp; &nbsp; &nbsp; 4.6.1. <a href=#coport>Listening Port</a><br>
105&nbsp; &nbsp; &nbsp; 4.6.2. <a href=#cosave>Save</a><br>
1064.7. <a href=#ephc>Ephemeris Corrections</a><br>
107&nbsp; &nbsp; &nbsp; 4.7.1. <a href=#ephcserver>Host & Port, Password</a><br>
108&nbsp; &nbsp; &nbsp; 4.7.2. <a href=#ephcmount>Mountpoint</a><br>
109&nbsp; &nbsp; &nbsp; 4.7.3. <a href=#ephcsys>System</a><br>
110&nbsp; &nbsp; &nbsp; 4.7.4. <a href=#ephcsave>Save</a><br>
1114.8. <a href=#clkrnx>RINEX Clocks</a><br>
112&nbsp; &nbsp; &nbsp; 4.8.1. <a href=#clkdir>Directory</a><br>
113&nbsp; &nbsp; &nbsp; 4.8.2. <a href=#clkint>Interval & Sampling</a><br>
1144.9. <a href=#orb>SP3 Orbits</a><br>
115&nbsp; &nbsp; &nbsp; 4.9.1. <a href=#orbdir>Directory</a><br>
116&nbsp; &nbsp; &nbsp; 4.9.2. <a href=#orbint>Interval & Sampling</a><br>
1174.10. <a href=#start>Start</a><br>
1184.11. <a href=#stop>Stop</a><br>
1194.12. <a href=#nw>No Window</a>
120</p>
121
122<p><a name="file"><h4>4.1. File</h4></p>
123
124<p>
125The 'File' button lets you
126<ul>
127<li>
128select an appropriate font.<br>
129Use smaller font size if the BNS main window extends beyond the size of your screen.
130</li>
131<li> save selected options.<br>
132Note that on Windows systems options are saved in register BKG_NTRIP_Server. On Unix/Linux systems options are saved in file ${HOME}/.config/BKG/BKG_NTRIP_Server.conf.
133</li>
134<li>
135quit the BNS program.
136</li>
137</ul>
138</p>
139
140<p><a name="help"><h4>4.2. Help</h4></p>
141
142<p>
143The 'Help' button provides access to
144<ul>
145<li>
146help contents.<br>
147You may keep the 'Help Contents' window open while configuring BNS.
148</li>
149<li>
150a 'Flow Chart' showing BNS linked to tools like BNC and a real-time GNSS engine such as RTNet.
151</li>
152<li>
153general information about BNS.<br>
154Close the 'About BNS' window to continue working with BNS.
155</li>
156</ul>
157</p>
158<p>
159BNS 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.
160</p>
161
162<p><a name="proxy"><h4>4.3. Proxy - for usage in a protected LAN</h4></p>
163
164<p>
165If 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.
166</p>
167<p>
168Note 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.
169</p>
170<p><a name="general"><h4>4.4. General Options</h4></p>
171
172<p><a name="logfile"><h4>4.4.1 Logfile - optional</h4></p>
173<p>
174Records 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.
175</p>
176
177<p><a name="appfile"><h4>4.4.2 Append Files</h4></p>
178<p>
179When 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.
180</p>
181
182<p><a name="eph"><h4>4.5. RINEX Ephemeris</h4></p>
183<p>
184BNS 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.
185</p>
186
187<p><a name="ephserver"><h4>4.5.1 Host & Port - mandatory</h4></p>
188<p>
189Enter 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.
190</p>
191
192<p><a name="ephsave"><h4>4.5.2 Save - optional</h4></p>
193</p>
194Specify the full path to a file where received Broadcast Ephemeris will logged. Beware that the size of this file can rapidly increase. Default is an empty option field meaning that logging is disabled.
195</p>
196<p>
197The following is an example log of Broadcast Ephemeris records in RINEX Version 3 Navigation file format for satellite GPS PRN32 and GLONASS PRN04:
198</p>
199
200<p>
201<pre>
202G32 2008 07 22 12 00 00 3.08818183839e-04 2.72848410532e-12 0.00000000000e+00
203 1.10000000000e+01 -4.00312500000e+01 4.63269297026e-09 9.74027926504e-01
204 -2.19419598579e-06 1.39143558918e-02 8.25151801109e-06 5.15381674576e+03
205 2.16000000000e+05 -8.56816768646e-08 -3.26801342873e-02 -2.94297933578e-07
206 9.68688494953e-01 2.30468750000e+02 -1.30607654294e+00 -8.26105839196e-09
207 -3.62872257943e-10 1.00000000000e+00 1.48900000000e+03 0.00000000000e+00
208 2.00000000000e+00 0.00000000000e+00 -2.79396772385e-09 1.10000000000e+01
209 0.00000000000e+00 0.00000000000e+00
210R04 2008 07 22 08 15 14 4.76110726595e-05 0.00000000000e+00 2.88600000000e+04
211 -1.76267827148e+04 -4.64202880859e-01 1.86264514923e-09 0.00000000000e+00
212 -1.79631489258e+04 -3.41343879700e-01 -2.79396772385e-09 6.00000000000e+00
213 -4.20270556641e+03 3.50097942352e+00 0.00000000000e+00 0.00000000000e+00
214</pre>
215</p>
216
217<p><a name="co"><h4>4.6. Clocks & Orbits</h4></p>
218<p>
219BNS requires GNSS clocks and orbits in the IGS Earth-Centered-Earth-Fixed (ECEF) reference system. They can be provided by a real-time GNSS engine such as RTNet and are expected to refer to the IGS Earth-Centered-Earth-Fixed (ECEF) reference system.
220</p>
221
222<p><a name="coport"><h4>4.6.1 Listening Port - mandatory</h4></p>
223<p>
224BNS is listening at an IP port for incoming GNSS clocks and orbits in a plain ASCII 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.
225</p>
226
227<p><a name="cosave"><h4>4.6.2 Save - optional</h4></p>
228<p>
229Specify the full path to a file where received clocks and orbits from a real-time engine will logged. Beware that the size of this file can rapidly increase. Default is an empty option field meaning that logging is disabled.
230</p>
231
232<p>
233Below you find an example of precise clocks and orbits coming in plain ASCII 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:
234</p>
235
236<p>
237<ul>
238<li>GNSS Indicator and Satellite Vehicle Pseudo Random Number</li>
239<li>X,Y,Z coordinates in Earth-Centered-Earth-Fixed system [m]</li>
240<li>Satellite clock error [ns]</li>
241<li>Standard deviation of satellite clock error [ns]</li>
242</ul>
243</p>
244
245</p>
246<p>
247<pre>
248* 1489 218527.000000 13
249G08 -76413.307 24866966.637 8527190.979 -162.790607 0.375
250G09 13547198.314 -14993483.355 16521052.798 6.462891 -0.335
251G12 23546505.279 -11419650.825 -4126405.941 -356.488306 -0.103
252G15 20671877.676 1926153.017 16592944.847 -147.015776 -0.216
253G17 14584397.556 20610108.909 8557082.997 38.709284 -0.081
254G18 8169428.184 -16862693.369 18872507.835 -153.553965 -0.149
255G22 -6624646.069 -14262545.420 21565075.194 211.479778 -0.089
256G26 21424721.760 7905958.802 13511083.183 296.893434 0.413
257G28 5220247.539 14404808.121 22087340.167 -21.263655 0.184
258R04 14087836.321 -12766880.844 16904727.671 47.601404 -0.302
259R13 9968458.843 4774687.770 22964489.920 -205.604626 0.526
260R14 11765674.558 -13533158.122 18154217.335 -142.409508 0.093
261R23 15142315.506 19152857.044 7329580.240 -111.465205 -0.316
262* 1489 218528.000000 13
263G08 -76893.521 24867989.053 8524186.937 -162.790606 0.376
264G09 13547066.674 -14991254.946 16523118.186 6.462896 -0.334
265G12 23547101.712 -11419571.961 -4123272.866 -356.488305 -0.102
266G15 20673380.091 1927636.846 16590899.052 -147.015776 -0.215
267G17 14583421.795 20609591.381 8559990.870 38.709276 -0.083
268G18 8171742.449 -16863250.285 18870956.178 -153.553959 -0.148
269G22 -6622069.142 -14263374.211 21565314.170 211.479771 -0.091
270G26 21425938.906 7907253.545 13508540.885 296.893448 0.415
271G28 5217668.842 14405642.686 22087373.519 -21.263659 0.183
272R04 14090047.809 -12767642.452 16902327.088 47.601401 -0.303
273R13 9967725.004 4777752.821 22964170.268 -205.604617 0.529
274R14 11764988.257 -13530761.727 18156438.374 -142.409512 0.091
275R23 15141704.650 19152042.802 7332976.247 -111.465201 -0.316
276</pre>
277</p>
278
279<p><a name="ephc"><h4>4.7. Ephemeris Corrections</h4></p>
280<p>
281BNS 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 GPS and GLONASS clock and orbit corrections.
282</p>
283
284<p><a name="ephcserver"><h4>4.7.1 Host & Port, Password - optional</h4></p>
285<p>
286Enter the NTRIP Caster's 'Host' IP name or number for stream upload.
287</p>
288<p>
289Enter 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).
290</p>
291</p>
292In 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).
293</p>
294
295<p><a name="ephcmount"><h4>4.7.2 Mountpoint - mandatory if 'Host' is set</h4></p>
296<p>
297Each 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.
298<p>
299
300<p><a name="ephcsys"><h4>4.7.3 System - mandatory if 'Host' is set</h4></p>
301<p>
302BNS refers its final clock and orbit corrections to a specific reference system. Available options are
303<p>
304<ul>
305<li>IGS05 which stands for the GNSS-based IGS realization of the International Terrestrial Reference Frame (ITRF2005), and</li>
306<li>ETRS89 which stands for the European Terrestrial Reference System 1989 adopted by EUREF.</li>
307</ul>
308</p>
309
310<p>
311<u>IGS05:</u>
312As 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.
313</p>
314<p>
315<u>ETRS89:</u>
316From 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:
317</p>
318<p>
319<pre>
320Translation in X: 0.054 m
321Translation in Y: 0.051 m
322Translation in Z: -0.048 m
323Rotation in X: 0.081 mas/y
324Rotation in Y: 0.490 mas/y
325Rotation in Z: -0.792 mas/y
326</pre>
327</p>
328<p>
329Note that the neglect of transformations 'IGS05->ITRF2005->ITRF2000' in BNS may cause discrepancies up to a maximum of 2 centimenters.
330<p>
331
332
333<p><a name="ephcsave"><h4>4.7.4 Save - optional</h4></p>
334<p>
335The 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.
336</p>
337<p>
338The file is in plain ASCII format comprising records containing the following set of parameters:
339</p>
340
341<p>
342<ul>
343<li>GPS Week</li>
344<li>Second in GPS Week</li>
345<li>GNSS Indicator and Satellite Vehicle Pseudo Random Number</li>
346<li>IOD referring to Broadcast Ephemeris set</li>
347<li>Clock Correction to Broadcast Ephemeris [m]</li>
348<li>Radial Component of Orbit Correction to Broadcast Ephemeris [m]</li>
349<li>Along-track Component of Orbit Correction to Broadcast Ephemeris [m]</li>
350<li>Cross-track Component of Orbit Correction to Broadcast Ephemeris [m]</li>
351</ul>
352</p>
353<p>
354The following is an example file contents based on combined GPS and GLONASS clock and orbit corrections carried in RTCM Version 3.x message Type 4056 and 4057:
355</p>
356<p>
357<pre>
3581489 325606.0 G31 18 -1.021 0.110 -1.308 -0.120
3591489 412006.0 R10 18 7.342 1.393 4.858 -2.634
3601489 412006.0 R19 18 4.696 2.358 1.707 -2.907
361...
3621489 325607.0 G30 80 6.022 0.591 -0.318 0.022
3631489 325607.0 G31 18 -1.022 0.110 -1.308 -0.120
3641489 412007.0 R10 18 7.341 1.390 4.860 -2.636
3651489 412007.0 R19 18 4.698 2.356 1.706 -2.906
366...
367</pre>
368</p>
369
370<p><a name="clkrnx"><h4>4.8. RINEX Clocks</h4></p>
371<p>
372The clock corrections generated by BNS can be logged separately in Clock RINEX format. The file naming follows the RINEX convention.
373</p>
374
375<p><a name="clkdir"><h4>4.8.1 Directory - optional</h4></p>
376<p>
377Here 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.
378</p>
379
380<p><a name="clkint"><h4>4.8.2 Interval & Sampling - mandatory if 'Directory' is set</h4></p>
381<p>
382Select the length of the Clock RINEX file generated. The default value is 1 day.
383</p>
384
385<p>
386Select 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.
387</p>
388
389<p><a name="orb"><h4>4.9. SP3 Orbits</h4></p>
390<p>
391The orbit corrections generated by BNS can be logged separately in SP3 Orbit files. The file naming follows the IGS convention.
392</p>
393
394<p><a name="orbdir"><h4>4.9.1 Directory - optional</h4></p>
395<p>
396Here 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.
397</p>
398
399<p><a name="orbint"><h4>4.9.2 Interval & Sampling - mandatory if 'Directory' is set</h4></p>
400<p>
401Select the length of the SP3 Orbit file generated. The default value is 1 day.
402</p>
403<p>
404Select 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.
405</p>
406
407<p><a name="start"><h4>4.10. Start</h4></p>
408<p>
409Hit '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.
410</p>
411
412<p><a name="stop"><h4>4.11. Stop</h4></p>
413<p>
414Hit the 'Stop' button in order to stop BNS.
415</p>
416
417<p><a name="nw"><h4>4.12. No Window - optional</h4></p>
418<p>
419On 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, see Config File example in the Annex) or from the register BKG_NTRIP_Server (Windows).
420</p>
421<p>
422The 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.
423</p>
424<p><a name="limits"><h3>5. Limitations</h3></p>
425<ul>
426<li>
427In Qt-based desktop environments (such as KDE) on Unix/Linux 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.
428</li>
429<li>
430Currently BNS can only generate the tentative RTCM Version 3.x message Type 4056 and 4057 for combined GPS and GLONASS orbit and clock corrections.
431</li>
432<li>
433We 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.
434</li>
435<li>
436Once BNS has been started, its configuration can not be changed unless without a restart. An on-the-fly reconfiguration is not implemented.
437</li>
438<br>
439</ul>
440<p><a name="authors"><h3>6. Authors</h3></p>
441<p>
442The 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.
443</p>
444<p>
445Georg Weber<br>
446Federal Agency for Cartography and Geodesy (BKG)<br>
447Frankfurt, Germany<br>
448[euref-ip@bkg.bund.de] or [igs-ip@bkg.bund.de]
449</p>
450
451<p><a name="annex"><h3>7. Annex</h3></p>
452<p>
4537.1. <a href=#history>History</a><br>
4547.2. <a href=#rtcm>RTCM</a><br>
455&nbsp; &nbsp; &nbsp; 7.2.1 RTCM <a href=#ntrip>NTRIP</a><br>
456&nbsp; &nbsp; &nbsp; 7.2.2 RTCM <a href=#rtcm3>Version 3.x</a><br>
4577.3. <a href=#config>Config File</a><br>
4587.4. <a href=#links>Links</a><br>
459</p>
460
461<p><a name=history><h4>7.1 History</h4></p>
462</p>
463<table>
464<tr></tr>
465<tr><td>August 2008 &nbsp;</td><td>Version 1.0 &nbsp;</td><td>[Add] Beta Binaries published.</td></tr>
466</table>
467</p>
468
469<p><a name="rtcm"><h4>7.2. RTCM</h4></p>
470
471<p>
472The 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.
473</p>
474<p>
475Personal copies of RTCM Recommended Standards can be ordered through <u>http://www.rtcm.org/orderinfo.php</u>.
476</p>
477
478<p><a name="ntrip"><h4>7.2.1 NTRIP</h4></p>
479
480<p>
481'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.
482</p>
483
484<p>
485NTRIP 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.
486</p>
487
488<p>
489NTRIP 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.
490</p>
491
492<p>
493NTRIP is an open none-proprietary protocol. Major characteristics of NTRIP's dissemination technique are:
494<ul>
495<li>Based on the popular HTTP streaming standard; comparatively easy to implement when having limited client and server platform resources available.</li>
496<li>Application not limited to one particular plain or coded stream content; ability to distribute any kind of GNSS data.</li>
497<li>Potential to support mass usage; disseminating hundreds of streams simultaneously for thousands of users possible when applying modified Internet Radio broadcasting software.</li>
498<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>
499<li>Enables streaming over mobile IP networks because of using TCP/IP.</li>
500</ul>
501</p>
502
503<p><a name="rtcm3"><h4>7.2.2 RTCM Version 3.x</h4></p>
504<p>
505RTCM 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.
506</p>
507RTCM 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 tentative messages currently under discussion of relevance to BNS are listed here:
508<p>
509<ul>
510<li>Message type 4050: GPS orbit corrections to Broadcast Ephemeris</li>
511<li>Message type 4051: GPS clock corrections to Broadcast Ephemeris</li>
512<li>Message type 4052: GPS code biases</li>
513<li>Message type 4053: GLONASS orbit corrections to Broadcast Ephemeris</li>
514<li>Message type 4054: GLONASS clock corrections to Broadcast Ephemeris</li>
515<li>Message type 4055: GLONASS code biases</li>
516<li>Message type 4056: Combined GPS and GLONASS orbit corrections to Broadcast Ephemeris</li>
517<li>Message type 4057: Combined GPS and GLONASS clock corrections to Broadcast Ephemeris</li>
518</ul>
519</p>
520<p>
521RTCM 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.
522</p>
523
524<p><a name="config"><h4>7.3. Config File</h4></p>
525<p>
526The following is an example of the contents of a Unix/Linux 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 :
527</p>
528<p>
529<pre>
530[General]
531clkPort=7000
532ephEcho=/home/weber/rinex/eph.rnx
533ephHost=clock-ip.bkg.bund.de
534ephPort=6000
535fileAppend=0
536font="Helvetica [Adobe],8,-1,5,75,0,0,0,0,0"
537inpEcho=/home/weber/rinex/ClocksOrbits.dat
538logFile=/home/weber/rinex/bns.log
539mountpoint_1=CLCK1
540mountpoint_2=CLCK2
541outFile_1=/home/weber/rinex/CLCK1
542outFile_2=/home/weber/rinex/CLCK2
543outHost=www.igs-ip.net
544outPort=2101
545password=serverPass
546proxyHost=
547proxyPort=
548refSys_1=IGS05
549refSys_2=ETRS89
550rnxIntr=1 day
551rnxPath=/home/weber/rinex
552rnxSampl=30
553sp3Intr=1 day
554sp3Path=/home/weber/rinex
555sp3Sampl=300
556</pre>
557</p>
558
559<p><a name="links"><h4>7.4 Links</h4></p>
560<table>
561<tr></tr>
562<tr><td>NTRIP &nbsp;</td><td><u>http://igs.bkg.bund.de/index_ntrip.htm</u></td></tr>
563<tr><td>EUREF-IP NTRIP broadcaster &nbsp;</td><td><u>http://www.euref-ip.net/home</u></td></tr>
564<tr><td>IGS-IP NTRIP broadcaster &nbsp;</td><td><u>http://www.igs-ip.net/home</u></td></tr>
565<tr><td>NTRIP broadcaster overview &nbsp;</td><td><u>http://www.rtcm-ntrip.org/home</u></td></tr>
566<tr><td>EUREF-IP Project &nbsp;</td><td><u>http://www.epncb.oma.be/euref_IP</u></td></tr>
567<tr><td>Real-time IGS Pilot Project &nbsp;</td><td><u>http://www.rtigs.net/pilot</u></td></tr>
568<tr><td>Radio Technical Commission<br>for Maritime Services &nbsp;</td><td><u>http://www.rtcm.org</u>
569</table>
570
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