[FOSS-GPS] RTKLIB: How to use it to develop a cheap DGPS basestation?

[John Morris]

Reading the raw receiver data and generating RTCM messages is pretty
straightforward.  If you have suggestions for setting up a  Kalman filter
for generating the correction data, that would be very helpful - my linear
algebra is not strong.  Better yet, if you know of any code for generating
the corrections, even if in Matlab, I could package it into a GPL package
for a base station.

-----Original Message-----
From: foss-gps-bounces at lists.osgeo.org
[mailto:foss-gps-bounces at lists.osgeo.org] On Behalf Of Tomoji Takasu
Sent: Saturday, November 13, 2010 6:44 AM
To: Open Source GPS-related discussion and support
Subject: Re: [FOSS-GPS] RTKLIB: How to use it to develop a cheap DGPS
basestation?

Dear Mauro

> I was trying to follow your code, looking for the step where the 
> PseudoRange Correction and the Rate Range Correction (PRC[m] + 
> RRC[m/s]) are generated for each satellite (based on the raw data from 
> the device used as base and the fixed position of it) before being 
> feed to the solution computation for the rover position (when using 
> DGPS mode), but I couldn't find it.

Current version (2.4.0) does not include RTCM output for DGPS or RTK base
station. Please use receiver raw proprietary messages for this purpose at
this moment.

I will add RTCM output function in the future version for raw pseudorange
and carrier-phase. I have not decided whether to support RTCM 2 PRC-type
DGPS correction for many existing receivers. If many requests, I will
consider it.

regards,

********
Tomoji TAKASU
WWW: http://gpspp.sakura.ne.jp


--------------------------------------------------
From: "Mauro Ugarte Avilés" <mauro.ugarte at cefop.udec.cl>
Sent: Friday, November 12, 2010 5:17 AM
To: <foss-gps at lists.osgeo.org>
Subject: [FOSS-GPS] RTKLIB: How to use it to develop a cheap DGPS
basestation?

> Dear Tomoji,
>
> DGPS base stations are much more expensive than some well known 
> receivers that can output raw data, and considering that RTKLIB can 
> use that data and correct the pseudoranges of a rover, I was thinking 
> if it is possible to use those corrections to output them as RTCM 
> SC-104 messages, thus developing a cheap DGPS base station using, for 
> example, some decent antenna, an u-blox 5T and RTKLIB with some addition.
>
> I was trying to follow your code, looking for the step where the 
> PseudoRange Correction and the Rate Range Correction (PRC[m] + 
> RRC[m/s]) are generated for each satellite (based on the raw data from 
> the device used as base and the fixed position of it) before being 
> feed to the solution computation for the rover position (when using 
> DGPS mode), but I couldn't find it.
>
> Can you please give me some advice at where to look on RTKLIB code for 
> that computation step? Any other suggestion, tip or comment about what 
> I'm trying to do will be more than welcome.
>
> Best regards to you and all list members,
>
> Mauro Ugarte A.
>
> PS.: For those of you wondering why do I want to use DGPS in the first 
> place, is because here in Chile there is nothing like WAAS, and I need 
> to increase accuracy on pedestrian rovers on rural areas, where the 
> ammount and quality of the data required for RTK are unachievable with 
> small GPS antennas and variable RF links.
> --
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