[FOSS-GPS] introduction and first help request

[Eugenio Realini]

Hi Mauro,

2010/5/27 Mauro Ugarte A <mauro.ugarte at cefop.udec.cl>:
> 1- First of all, in Chile there is nothing like a GPS reference station
> network providing corrections on NRTK/NTRIP, which we could rely on. There
> is an IGS station, though. It is near our lab (about 3 km), codenamed CONZ
> and labeled "highrate_permanent" under GNSS/files > Data Archive > File
> Browser at GNSS Data Center website (http://igs.bkg.bund.de/index/index) and
> provides RINEX files that should help at post-processing but not for real
> time aplications (please correct me if i'm wrong).

I checked here http://www.igs-ip.net/home and it seems that CONZ
station data can be accessed via NTRIP:

IP: www.igs-ip.net
Port: 2101
User & pass: you have to register here http://igs.bkg.bund.de/ntrip/registeruser

This is the source table line for CONZ:

STR;CONZ0;Concepcion-TIGO;RTCM
3.0;1004(1),1006(15),1008(15),1012(1),1019,1020,1033(15);2;GPS+GLO;IGS;CHL;-36.84;286.98;0;0;LEICA
GRX1200GGPRO;none;B;N;3600;BKG

It already has all the messages you could want, and if it is not
located where you need it to be, at least you can use it for some
initial testing!

> 1- Should we buy a RTK capable reference station module, that outputs
> RTCM-RTK messages to use them as an input to rtklib/gogps? (example:
> magellan DG-14), or could we use another low cost module that outputs raw
> data measurements and "convert" that raw data into the corresponding
> RTCM-RTK messages to feed rtklib/gogps?. I ask this because it seems to me
> that RTCM V3.1 messages broadcasted by RTK reference stations (1001-1002 for
> precision GPS L1 only, 1003-1004 for precision GPS L1 & L2) could be
> "constructed" by raw data output, and messages 1005-1006 too, using the
> station position. Is all this possible or am i missing something?

That is right, you can do it either ways: buy a module with RTCM
output or construct RTCM once you got raw data. Obviously the second
option requires much more work and trial&error.

> 2- Do you know alternatives to LEA-4T, at low cost, that seems to you that
> should stay around at least a couple of years and output raw data which we
> can feed (or convert to feed) to rtklib/gogps?. We know that there are the
> u-blox LEA-5T and LEA-6T, but those output raw data at 2 Hz and 5 Hz
> respectively, and the last one is just born so firmware bugs could happen as
> they happened to LEA-5T, so if you know another faster and cheaper, please
> let me know.

Do you really need 10Hz for pedestrian rovers? If you mean for
broadcasting RTCM, permanent stations I know about broadcast at 1 Hz.
As for firmware bugs, they can happen with everything... let's hope
u-blox people learned from 5T mistakes and that 6T will be better ;)

Interesting project, anyway! Please keep us updated.

Eugenio