Re: [FOSS-GPS] information
Francesco Mancino:
Well as a practical matter, you really do not to want to record
RINEX in the field, it is better (much smaller) to use the device's
native binary format or an RTCM3 format and post process that to
RINEX.
> I've not RINEX files of local observations taken by a rover
I am not sure I read this correctly but the above statement remains
true.
> So I'm thinking to use RINEX observation data of a network
station like rover static data and correct them with NRTK-VRS
technique.
Should work fine. For this you need to gather either live caster
data (use a free tool like SNIP and have it record whatever NTRIP
data stream you need, see: use-snip.com) or use after the fact FTP
data.
You may be able to use the FTP files provide by NGS and CORS. The
problem that many people have with those files is that after a week
the data is decimated for long term storage, so your 1Hz data
becomes 5/15 second data. So it is common to record the live data
when you can get it off NTRIP and make your own records. [Beside
SNIP, the BNC tool is also adept at this] Another issue is that NGS
is only interested in high grade base stations about 70km apart, and
many states in fact have sites with closer spacings. As matter of
current policy, NGS does not record those. Its worth the time and
trouble to learn about who has local stations you might want to get
data from. If you are limited to L1, you really need to find a
station that is <15km from your rovers to do RTK things.
The other advantage of post processing is you can use better orbital
and clock products which you can get from various places (and you
can also get live from many NTRIP sources).
On the whole your approach is quite sound IF (the big if) your L1
only rover devices can in fact give code (pseudorange) AND carrier
data. If it can only give you code, you are more or less screwed.
[If that is the case, try to send it RTCM2.x data because is
probably has some sort of primitive Hatch filter to do some carrier
smoothing and multipath rejection]
Good luck with this.
Regards, David Kelley
PS: the carrier field in any RINEX file is the "L" (L1 or L2 etc.),
if you do not see that field you do not have carrier data, here is a
fragment from a uBlox 6T (an L1 only device). You can see the
carrier for SV "G20" was missing in this data set (which was
dropping out of view as the high negative Doppler rate and low SNR
shows).
4 C1 L1 D1 S1 # /
TYPES OF OBSERV
2016 6 7 17 42 46.781 GPS
TIME OF FIRST OBS
2016 6 7 18 3 27.781 GPS
TIME OF LAST OBS
END OF HEADER
16 6 7 17 42 46.781 0 12G 7G
8G26G20G21G15G16G27G18G10S20G 4
24315075.481 127776517.3292 448.410
29.000
22629267.575 118917537.1101 2271.698
32.000
21895722.936 115062756.905 -3156.582
42.000
25179786.705 -3549.886
20.000
23308387.593 122486312.002 -2759.055
46.000
25514482.824 134079506.961 333.453
33.000
20601440.208 108261249.8101 -1454.798
43.000
20620768.706 108362926.6981 797.603
40.000
22056801.307 115909274.4371 -833.425
46.000
21617601.357 113601266.278 1698.172
47.000
37871568.996 199016439.7911 -286.053
29.000
23186586.975 121846252.716 -3871.296
40.000
On 10/10/2016 5:55 PM, Francesco
Mancino wrote:
David,
thanks for your suggestions. My main problem is the lack of a
specific HW ( receiver and antenna ), so I've decided to
operate in a Post Processing mode. Here, I have another
problem : I've not RINEX files of local observations taken
by a rover. So I'm thinking to use RINEX observation data of
a network station like rover static data and correct them with
NRTK-VRS technique. Please, give me a feedback about my idea.
Thanks in advance.
FM
Da:
FOSS-GPS per
conto di David Kelley
Inviato: mercoledì 21 settembre 2016 01.00
A: foss-gps@lists.osgeo.org
Oggetto: Re: [FOSS-GPS] information
Re: [FOSS-GPS] information
David, thanks for your suggestions. My main problem is the lack of a specific HW ( receiver and antenna ), so I've decided to operate in a Post Processing mode. Here, I have another problem : I've not RINEX files of local observations taken by a rover. So I'm thinking to use RINEX observation data of a network station like rover static data and correct them with NRTK-VRS technique. Please, give me a feedback about my idea. Thanks in advance. FM Da: FOSS-GPS per conto di David Kelley Inviato: mercoledì 21 settembre 2016 01.00 A: foss-gps@lists.osgeo.org Oggetto: Re: [FOSS-GPS] information Francesco Mancino: You do not need to send NMEA from it, you probably need to send RTCM to it. You probably can not do classical RTK with it. If you are planning to use a DGPS corrections (not RTK), then it is likely the GNSS chip itself will do the navigation filter for you (in other words it is not externally done with RTKLIB and RTKnavi). If that is your chosen path, seek for a local RTCM2.x data stream (local meaning <50km or so) and figure out how to send that data directly to you GNSS. I am not familiar with the "Emtac BT GPS receiver" but a quick web search tells me that is uses the older SiRF Star II LP chip set and therefore it seems to use only WAAS/EGNOS corrections. You need to research that point first and foremost to be sure that it can accept DGPS from other sources. As far as I am aware you will not get code and carrier from it, so there is not means to do an RTK style navigation solution. RTKLIB can do a DGPS navigation solution, if you can get raw code from it. Regards DC Kelley On 9/18/2016 5:34 PM, Francesco Mancino wrote: Hi, I'm using an Emtac BT GPS receiver to acquire gps signals but RTKNAVI does not support NMEA0183 format as Rover input stream. Please can you give me any suggestions to realize an input stream ( for a DGPS application ) without changing the receiver? ___ This message is sent to you from FOSS-GPS@lists.osgeo.org mailing list. Visit http://lists.osgeo.org/mailman/listinfo/foss-gps to manage your subscription For more information, check http://wiki.osgeo.org/wiki/FOSS-GPS
Re: [FOSS-GPS] information
Francesco Mancino: You do not need to send NMEA from it, you probably need to send RTCM to it. You probably can not do classical RTK with it. If you are planning to use a DGPS corrections (not RTK), then it is likely the GNSS chip itself will do the navigation filter for you (in other words it is not externally done with RTKLIB and RTKnavi). If that is your chosen path, seek for a local RTCM2.x data stream (local meaning <50km or so) and figure out how to send that data directly to you GNSS. I am not familiar with the "Emtac BT GPS receiver" but a quick web search tells me that is uses the older SiRF Star II LP chip set and therefore it seems to use only WAAS/EGNOS corrections. You need to research that point first and foremost to be sure that it can accept DGPS from other sources. As far as I am aware you will not get code and carrier from it, so there is not means to do an RTK style navigation solution. RTKLIB can do a DGPS navigation solution, if you can get raw code from it. Regards DC Kelley On 9/18/2016 5:34 PM, Francesco Mancino wrote: Hi, I'm using an Emtac BT GPS receiver to acquire gps signals but RTKNAVI does not support NMEA0183 format as Rover input stream. Please can you give me any suggestions to realize an input stream ( for a DGPS application ) without changing the receiver? ___ This message is sent to you from FOSS-GPS@lists.osgeo.org mailing list. Visit http://lists.osgeo.org/mailman/listinfo/foss-gps to manage your subscription For more information, check http://wiki.osgeo.org/wiki/FOSS-GPS
[FOSS-GPS] information
Hi, I'm using an Emtac BT GPS receiver to acquire gps signals but RTKNAVI does not support NMEA0183 format as Rover input stream. Please can you give me any suggestions to realize an input stream ( for a DGPS application ) without changing the receiver? ___ This message is sent to you from FOSS-GPS@lists.osgeo.org mailing list. Visit http://lists.osgeo.org/mailman/listinfo/foss-gps to manage your subscription For more information, check http://wiki.osgeo.org/wiki/FOSS-GPS
