Don't forget, Google Navigation is vector based. It can easily perform a "snap to road" trick to make you think it is more accurate. The Maps API only has raster maps and thus is unable to cheat on the position accuracy.
On Friday, August 3, 2012 4:36:01 PM UTC-4, bob wrote: > > It may use extrapolation but not necessarily based on the route. > > I would think it could easily be based on the estimated velocity of the > vehicle, the last known position and the time since the last known position. > > > > On Friday, August 3, 2012 1:47:15 PM UTC-5, Nadeem Hasan wrote: >> >> That would be extrapolation. And that is actually the exact reason why >> the GPS lags on exits if they are off-route because it has extrapolated >> your position based on your route till the next actual GPS location update >> arrives. I have seen this behaviour with my Garmin device too when I decide >> not to follow the route. >> >> On Friday, August 3, 2012 11:46:45 AM UTC-4, Nobu Games wrote: >> >>> I'd go for interpolation and take the current average speed and the >>> "structure" of the streets into account. That of course only works when you >>> have something like a graph / vector representation of the streets and know >>> how they are connected and what orientation they have. >>> >>> It is also pretty common that even Google Navigation is off, especially >>> on highways with exits. Sometimes the navigation draws the car following >>> the highway even though you are already leaving on an exit. >>> >>> >>> On Wednesday, August 1, 2012 9:18:33 AM UTC-5, bushido wrote: >>>> >>>> Hi all, >>>> >>>> I'm writing an application for android for which I need good position >>>> accuracy, I use a Galaxy Nexus as test device. >>>> >>>> My test application subscribes to location updates and draws a car >>>> symbol in a map, the map is centered to the location of the car & >>>> rotates according to the bearing of the location (exactly like google >>>> maps on android does). I noticed that when up to speed, the positions >>>> don't match with reality, they lag behind considerably. >>>> When I cross a street at 90km/h for example, it will take a few >>>> seconds before the car on the map is also crossing that street. It >>>> isn't an error in the map data, because when I'm standing still, the >>>> car gets drawn on the correct location. Google maps for android shows >>>> exactly the same behavior. >>>> >>>> The position of the car in Google Navigate on the other hand matches >>>> reality rather closely. I've noticed that the position updates are a >>>> lot smoother as well. (10Hz rather than the 1Hz updates which you get >>>> from GPS) >>>> >>>> My question is: how do they do it? What I can think of is: >>>> - using the phone's sensors (gyro & accelero) together with a kalman >>>> filter or similar. But I can't see how you could make that work for >>>> every phone, since not all phones have these sensors. >>>> - interpolating, but in that case I would expect overshooting when >>>> there is a sudden stop or a sharp corner >>>> >>>> Thanks in advance. >>>> Bushido >>>> >>> -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
