John,
Thanks for the great info below (forwarded as requested).
Do you happen to know which Garmins are based on the Sirf
III chips (so I can avoid them)?
Here are a few other GPS data processing software sites
I've found (but haven't used the software):
Teqc
http://facility.unavco.org/software/teqc/teqc.html
http://www.ngs.noaa.gov/gps-toolbox/
http://mywebpages.comcast.net/dmilbert/softs/
http://home-2.worldonline.nl/~samsvl/software.htm
A low-cost system:
https://shop.delorme.com/OA_HTML/DELibeCCtdItemDetail.jsp?item=18902§ion=10059
Brent Fraser
GeoAnalytic Inc.
Calgary, Alberta
----- Original Message -----
From: "John Morris" <[EMAIL PROTECTED]>
Cc: <[EMAIL PROTECTED]>
Sent: Wednesday, August 08, 2007 12:29 AM
Subject: RE: [Geowanking] Cheap post-process DGPS - why not?
> Brent - I posted earlier, but the message never made it to
the list. Perhaps
> you could forward this?
>
> Thanks,
> John Morris
>
> ----------------------------------------------------------
------------------
> ---------------------------------
>
> There are several inexpensive GPS receivers which can be
used with
> post-processing. The trick is finding good software which
doesn't break the
> budget.
>
> Some free software possibilities I've heard of:
> o The Gps Toolkit has a "DDBase" program for
postprocessing.
> o Canadian Precise Positioning Service (Brent
mentioned it as well)
> o PPro2 demo version. (www.kinematicgps.com). Free
demo mode for
> pre-2006 Rinex data.
> o My own non-working software at
www.precision-gps.org.
> o The OPUS service. (I didn't realize it supported
single frequency
> receivers)
> o ...
>
> (Please respond and help fill in the list!)
>
> The older Garmins were the first widespread consumer
receivers to produce
> raw measurements. Garmin didn't officially support raw
measurements until
> the GPS16 and GPS18 came out, at which point they
documented the protocols.
> The latest Garmins are based on the Sirf III chip which is
completely
> different. Sirf III produces "smoothed" pseudoranges and
no carrier phase.
> Sirf III receivers might work for static measurements,
assuming "smoothing"
> doesn't get in the way.
>
> (BTW - I have a pair of GPS18's if somebody wants to
experiment with them.)
>
> If you are serious about postprocessing, you may want to
look at OEM boards.
> The Thales AC12 and u-blox 4T both give high quality
carrier phase at
> relatively low prices ($150-$200). The problem is, you
have to do a bit of
> soldering to make them work.
>
> I absolutely agree with Brent about starting simple.
Static processing is
> much easier than carrier phase kinematic processing. If
you have a good
> receiver and a base station within 10 miles, you can often
get submeter
> static positions within 30 seconds. It is a
straightforward (?) application
> of least squares. I added the "?" because GPS is never
straightforward by
> the time you're done with it.
>
> I've been fantasizing about creating a web service for
static
> postprocessing. The idea would be to use a cell phone with
a Bluetooth Sirf
> III GPS. The service would let you upload a 30 second
batch of pseudoranges
> and give back an immediate position.
>
> - John Morris
> (with more good intentions than time to execute them)
>
>
>
>
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