How does GPS on android get the altitude?

Question

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.

Answer 1

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

Answer 2

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.