How Is Altitude Calculated From Earth's Radius and Satellite Distance?

[aeromat]

The Problem:
Why is it that r = r_rE + h?

r = distance from Earth's centre to satellite
r_rE = Earth's radius
h = altitude

Why is it that you find altitude by subtracting Earth's radius from radius? How does that make sense..

 

[gneill]

The Problem:
Why is it that r = r_rE + h?

r = distance from Earth's centre to satellite
r_rE = Earth's radius
h = altitude

Why is it that you find altitude by subtracting Earth's radius from radius? How does that make sense..

What is your definition of altitude?