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drøn, there is a "neoretro" photo thread on the french forum pignonfixe.fr about that, maybe you'll find some examples you like:
http://www.pignonfixe.com/showthread.php?tid=97557 -
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There is also Track Navigator on Android, I haven't used it yet but it seems good for navigation from a gpx file
https://play.google.com/store/apps/details?id=com.thunkmonkey.tracknav&hl=en -
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I can't agree with this. GPS receivers in devices receive a signal which is transmitted by satellites. Satellites transmit location data (of the satellite at time of transmission), you receiver receives this information and calculates the position based on a minimum of 3 satellites worth of data (technically 4 is the minimum but the fourth is required for time delay on the data rather than position information). The location of the satellite, and the time taken for the data to reach the receiver allows the device to calculate the distance. This distance is the distance you are from the satellite in any direction. Although the satellite is pointing towards Earth, the data packet doesn't have the direction in which the satellite is pointing, so the receiving device assumes your position in relation to the satellite is any possible direction at the calculated distance. So where the 3 spheres of possible locations intersect is where you are. It's not the intersection of 3 circles but 3 spheres. You think it's 3 circles because maps are 2D, not 3D with elevation, but your device is always calculating a 3D position. There are always multiple possible positions because the spheres intersect at more than once altitude. Your device usually ignores the higher altitude as it is deemed to be too high.
To say that a GPS device is more accurate in 2 of the 3 axes makes no sense whatsoever. The breakdown is applying the calculated 3D position to a 2D map.
I thought the angle between satellites would affect the precision of the intersection calculation, hensc the worst Z direction error:
http://www.gpsinformation.net/main/altitude.htmbut further reading agree with you that it's not the case:
http://www.gpspassion.com/forumsen/topic.asp?TOPIC_ID=147960I'll try to sort things out, it's always interesting to know how things work. Thanks for pointing this out !
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Also, Strava import doesn't ignore altitude coordinates if they are from a Garmin GPS that have a barometric altimeter (such as the Edge 500 and up), but will strip the altitude and replace it with mapped altitude from NASA elevation maps for all other devices. I would be really interested by a side-by-side comparison of these Garmin vs pressure-sensor-equipped phones with a good software.




Could maybe have something like pointy screws to keep people from sitting on it?