Hi all, I have been using http://www.malsingmaps.com/ routable map for my Garmin C330, for about a month now. And it work great!
I am not active in the MalSingMaps community. But from what I know, they have been using consumer grade GPS to map all the roads network. On 8/6/07, Simon Garton <[EMAIL PROTECTED]> wrote: > > > Hi all, > > I have tried that approach with a pair of cheap GPSs and wrote the > software > to automatically do the add/subtract. Got absolutely rubbish results - > even > with two of the same model of GPS. I guess it is something to do with them > not choosing the same set of satellites to use - certainly on inspection > they were tracking different sets. At one point I had three GPSs on the > table, reasonably clear location, and all three were drifting in different > directions from the true location. > > A mate also found this quote : > > "Q. Can I post-process the data collected with my Garmin GPS unit to > obtain > greater accuracy? A. Unfortunately not. Garmin GPS units and other > handheld > consumer-grade units do not internally store the raw pseudorange data from > the satellites required to post-process differential corrections. This > type > of capability is only found in survey-grade GPS equipment." > > Would be very interested in at least an algorithm for doing this > correction > ... > > Simon > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Ben Discoe > Sent: Monday, 6 August 2007 1:44 p.m. > To: [email protected] > Subject: [Geowanking] Cheap post-process DGPS - why not? > > Hi list, > > Like a great many people, i can afford consumer GPS units (~$100) but not > a > 'professional' unit (~$4000-8000). Of course, the well-known lack of > accuracy in consumer units (~10m) is nowhere near usable for many > applications. > > The solution that springs to mind would be a cheap differential: > 1. Buy a second consumer GPS unit. > 2. Tie it to a post or other fixed object. > 3. Walk around, gathering data with the first GPS. > 4. Download data from both units. > 5. Using the timecode to correlate, subtract the second unit's drift from > the first unit's coordinates. > > >From everything i've read, it seems to me that would bring the 5-10m > error > down to 1-2m. However, i didn't find any software to do this simple > operation. > > There is plenty of information out there about fancier DGPS using WAAS or > other things which are not widespread and/or not reliable > (http://www.gpsinformation.org/dale/dgps.htm) > > There is high-end proprietary software like GrafNav > (http://www.novatel.com/products/waypoint_grafnav.htm) which apparently > costs thousands of dollars. > > But it should be a really simple operation to subtract one track's offset > from another. Is there some reason this simple approach wouldn't > work? Is > there some FOSS which will do it? > > Thanks, > Ben > http://vterrain.org/ > > > _______________________________________________ > Geowanking mailing list > [email protected] > http://lists.burri.to/mailman/listinfo/geowanking > > _______________________________________________ > Geowanking mailing list > [email protected] > http://lists.burri.to/mailman/listinfo/geowanking > > >
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