I'll take a stab at precision vs accuracy. High precision: Osmand reports the same value within a very small range for a reference elevation every time. If reference is 292 feet, I would consider repeated indications of 262 feet to be very precise, though not correct. High accuracy: Osmand shows the correct value for the 292 ft reference elevation. If Osmand reports 292 feet exactly I'd consider that highly accurate. If an hour later Osmand then shows 414 feet at the same position, that report is not accurate. If it later shows 210 feet that too is not accurate. If more readings showed continued variation despite being spot on occasionally, I'd conclude that the device has low precision.
<https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=icon> Virus-free. www.avast.com <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=link> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> On Sun, Feb 18, 2018 at 3:44 PM, Isaac <[email protected]> wrote: > The discrepancy between devices was my fault - I just realized that I had > uninstall the world altitude correction map but the altitude corrections > did not revert at that point. Seems a little strange to me, but the higher > value only reverted after rebooting the device. It now matches the already > corrected value that is output from the Garmin. > > The "Bluetooth GPS" app that I use also allows for geoid correction, so it > theoretically can be applied as many as three times if that box is checked > in addition to the osmand and Garmin corrections. > > On Sunday, February 18, 2018 at 1:36:12 PM UTC-5, Greg Troxel wrote: > >> >> Poutnik <[email protected]> writes: >> >> > For me, it looks like both internal GPS units, in agreement with my >> > experience, do not provide geoid correction to the amplitude. Therefore >> > is is about 120' lower than the reference, what is about the correction >> > value for US region. >> >> The Android specification is to return ellipsoidal height: >> >> https://developer.android.com/reference/android/location/Location.html >> >> and one can get the NMEA also and use either geoid height or GPGGA >> (orthometric) height: >> >> https://stackoverflow.com/questions/2791927/how-does-getalti >> tude-of-android-gps-location-works#2797026 >> https://stackoverflow.com/questions/9361870/android-how-to- >> get-accurate-altitude >> >> The real question is what's up with the external unit and how that >> works. If it's being connected in to replace the internal GPS and >> accessed via the same interface, it needs to report ellipsoidal height. >> But the fact that it shows the higher (presumably close to correct for >> orthometric height) value in satstat on both phones leads me to believe >> that the android location/altitude (misnamed) interface is being used to >> get the orthometric height from the bluetooth unit. That's the big >> mystery. >> >> The other mystery is that one of your phones seems to have the elevation >> correction map in OsmAnd and the other does not. >> >> Probably OsmAnd should change the symbol to something other than >> mountain, perhaps "EH", to indicate that it's showing ellipsoidal >> height, or make it red. >> >> -- > You received this message because you are subscribed to the Google Groups > "Osmand" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- Robert Grant -- You received this message because you are subscribed to the Google Groups "Osmand" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
