Originally Posted by
Looigi
It is possible for a GPS receiver determine velocity via doppler shift of the satellite signals, which doesn't need two positions and times. It's a bit complicated but that is why I said speed was determined is "possibly based on the time between successive positions". Here's a good writeup on it:
http://www.aprs.net/vm/gps_cs.htm
Yes, there's the doppler shift stuff (forgot about that).
http://www.kowoma.de/en/gps/positioning.htm
It's not clear which method is used.
http://nujournal.net/HighAccuracySpeed.pdf
http://continuouswave.com/ubb/Forum6/HTML/002179.html
I suspect that "consumer grade" GPS don't use doppler.
Originally Posted by
Looigi
Agree, the hard part is done, position/time points are determined. But Glympse only provides a website with a map showing the current location being reported. It only shows the current position, not any previous positions, so no track. The spatial and time coordinates are not there, just a graphic map. You would have to write software of some sort to interpret the map and figure out the coordinates. Sounds pretty hard to me. Or maybe you could get the author to provide coordinates in some way.
It shows the current position on a map, doesn't it? A track is just a list of multiple "current" positions (connected by line segments). If you can show one position on a map, it's easy to show any number of them. Dealing with just one point simplifies things like data storage.
Originally Posted by
Looigi
Of course the easy way to do this is to use and app like Strava or MMR, etc, which do record tracks and data.
I'd guess that Glympse is choosing to keep things simple so they don't have to pursue these established "big guns" and match features. That is, they are occupying the niche of providing simple location (a niche that doesn't have a lot of competition).