## gpsbabel-code

 [Gpsbabel-code] KML Average Speed Calculation From: Thomas J. Baker - 2008-06-15 15:31:19 ```With gpsbabel 1.3.5, the kml writer now outputs an average speed which appears to be a simple total distance / total time calculation. My question is how useful is that simple of a calculation given that many typical GPS tracks contain stops/pauses of one type or another. I know with the myriad of GPS receivers supported, they all do things differently and these stops are probably not articulated in the data, nor might it be possible to articulate it. Maybe I'm just a victim of such a GPS. In my experience with 20 to 100 mile bike rides with my Garmin 305 set to auto-pause, the average of all the speeds at each point has proven to be pretty accurate. I guess you could call this the moving average. I know this too has inherent inaccuracies. Given a reasonable sampling rate, it at least seems like a potentially useful piece of data given how poor the simple calculation can be in these situations. What are people's thoughts on this? Is this worth pursuing? FWIW, I've submitted patches to the kml writer before. Thanks, tjb -- ======================================================================= | Thomas Baker email: tjb@... | | Systems Programmer | | Research Computing Center voice: (603) 862-4490 | | University of New Hampshire fax: (603) 862-1761 | | 332 Morse Hall | | Durham, NH 03824 USA http://wintermute.sr.unh.edu/~tjb | ======================================================================= ```
 Re: [Gpsbabel-code] KML Average Speed Calculation From: Robert Lipe - 2008-06-16 19:21:30 Attachments: Message as HTML ```On Sun, Jun 15, 2008 at 10:31 AM, Thomas J. Baker wrote: > With gpsbabel 1.3.5, the kml writer now outputs an average speed which > appears to be a simple total distance / total time calculation. My > question is how useful is that simple of a calculation given that many > typical GPS tracks contain stops/pauses of one type or another. I know It's a no-win. Runners and bicyclists tend to care about moving averages and other activities want start/end averages. We could provide an option to provide either, I suppose; GPSBabel really needs some more options. :-) Most GPSes don't really put a mark in the data when you're not moving; you'd have to calculate it on a per-trackpoint basis based on the speed or something. So you'd need to pass in a threshold of how fast is "not moving". A car driving at 3mph probably isn't sensible to consider "moving", while 3mph is a reasonably spritely walk. > In my experience with 20 to 100 mile bike rides with my Garmin 305 set > to auto-pause, the average of all the speeds at each point has proven to > be pretty accurate. I guess you could call this the moving average. I > Edge and Forerunner have this in their firmware, but I don't think they push it out to the tracks. ```