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I want to know:

1) How gps receiver on android get the altitude from the satellites?

2) How many satellites which it use ?

3) How many way to get the altitude ? As I found on the Internet, there are 2 kinds such as SensorManager and LocationManager. In this case, I might be wrong. Please correct me.

4) What altitude data are represented ? elevating ? degree? distance from what to what ?

I tried to search these questions, but the information is pretty hard to find. So, please explain to me, all experts.

Appreciate all helps.

Yoo
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    Kind of a duplicate question with an answer: http://stackoverflow.com/questions/2791927/how-does-getaltitude-of-android-gps-location-works – Donn Felker Oct 11 '12 at 02:58

2 Answers2

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  1. Each GPS satellite knows its position and time very precisely, and transmits this information continuously. The signal takes time to travel to earth, and the receiver uses the differences in the delay of the signal arrival time to calculate the three position variables (lat, long, alt) and the current time.
  2. A minimum of 4 satellite signals is needed for a full solution. In most cases 6 to 12 satellites are visible to the receiver.
colechristensen
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4) Altitude will be in meters above the WGS 84 reference ellipsoid. This measurement is difficult to get precisely due to the Earth's shape. The LocationManager is not to be trusted with regards to altitude, you will probably get a 0 outside, but an 8 if you go inside a building

sea cat
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  • This answer doesn't seem to answer the question. – nadavvadan Sep 07 '17 at 14:23
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    As @nadavvadan already stated this doesnt really answer the question, consider adding this information as a comment on the question tho. – Fabian S. Sep 07 '17 at 14:37
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    @FabianSchöner users with less than 50 reputation cannot comment if I recall correctly. – nadavvadan Sep 07 '17 at 14:45
  • @nadavvadan thats a true, my bad. – Fabian S. Sep 07 '17 at 14:47
  • @nadavvadan I lack the reputation to do that. And how does that not answer the question? "What does the altitude value represent?" -> "**Meters above the WGS 84 reference ellipsoid**". Granted it only answers one of the questions, but it's still an answer. Why is the other one, only hitting 2 points, not voted down? – sea cat Sep 08 '17 at 09:34