Differential GPS via mobile Internet

[Bob Hall]

I have a unique problem that hopefully someone here has some experience with. I am responsible for the site design and lay out for a fairly large festival (Tulsa OktoberFest). We have over 100,000 square feet of tent that go up on a site that because of undulations and curves does not have a grid or straight lines. To keep the Fire Marshal happy we have to maintain very specific distances between the tent rope stake lines. Generally I have to locate and mark the tent installations to within at most 5 feet of tolerance. I have been doing this specific task for 12 years and have developed measurements from fixed landmarks with respect to angle and distance.

The problem is after the 2011 everything gets bull dozed and rebuilt. This five hour task will become a 25-30 hour one. I had my Garmin along today and with between 9 and 11 satellites visible, the best I could see was +/- 15 feet. No where precise enough.

My Sprint wireless card doesn’t get much use this time of year, and surely someone is doing DGPS corrections over the Internet in real time. Five or six hours of Google searches have led me to mostly dead links and commercial services.

Any help would be greatly appreciated.

 

[David Wolfson]

I think unprocessed DGPS, now aka WAAS, can marginally get you the +-1m if your receiver is actually giving you the DGPS fix. Log the observations over 30 seconds or so and average to reduce the RMS error.

But I'd try the administrative solution first. Get in touch with the Tulsa Public Works Department. Their survey section surely has higher level equipment that can get you +-3" or so. Explain the situation, i.e. the FD needs this for the Oktoberfest, and I'll bet you a large Weissbier they'll spot you the reference points you need at no charge.