Re: GPS measured elapsed distance
- From: Robbie <robbiex@xxxxxxxxxxxxx>
- Date: Fri, 15 Apr 2005 18:57:17 -0400
Chris Malcolm wrote:
Robbie <robbiex@xxxxxxxxxxxxx> writes:
I would like to share programming experience with those who have worked on public domain software for GPS measurement of elapsed distance.
There are two basic approaches: one using rate x time and the other adding the distances between frequently obtained coordinates along a track. It is not a trivial problem due to position variability when the GPS is not in motion, limitations of the (PDA) programming languages regarding date-time data, and difficulties obtaining a regular "time tick" that is synchronized with the transmission of the GPS motion data.
Why do you need special software? I find that the trip distance total on my GPS matches to the distance recorded by my bicycle computer (based on wheel revolutions) to within 2%. On the few times when it goes from less than 2% to more than 2% but less than 5% the reason is obvious and easily discovered by inspection or by software: loss of satellite reception for some time. And once in a few hundred trips I got an error of a few thousand per cent, but again the reason was obvious: a spurious position fix which had me travelling hundreds miles at near the speed of light.
BTW, you shouldn't even be working with such a crap programming language that you actually have "limitations with regard to date-time data"! -- Chris Malcolm cam@xxxxxxxxxxxxxxxxxxxx +44 (0)131 651 3445 DoD #205 IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK [http://www.dai.ed.ac.uk/homes/cam/]
Hi Chris,
GPS data are displayed on a PDA. We need to be able to control the content, size and position of window displayed navigation variables. The GPS mapping program does not have this capability. Johan Franson's GPSTools provides easy access to speed, heading, coordinates and other data. The 2.20 version released today, 4/15/2005, has a Position.Distance function that computes distance between coordinates by either the great circle or Pythagoras theorem methods. It is obviously important to screen the input data, but sampling at 1 sample/second should provide fairly good track data.
I agree about the poor programming tools, but also know that the PDA hardware imposes some limitations on "real time" computations.
Robbie
Robbie
.
- References:
- GPS measured elapsed distance
- From: Robbie
- Re: GPS measured elapsed distance
- From: Chris Malcolm
- GPS measured elapsed distance
- Prev by Date: Re: Low cost GPS data logger -- map features not needed
- Next by Date: Re: How do I find acreage?
- Previous by thread: Re: GPS measured elapsed distance
- Next by thread: Re: GPS measured elapsed distance
- Index(es):
Relevant Pages
|
