Angle of Elevation in Earth Coordinate Systems Does a calculated angle of elevation differ between earth centered earth fixed (ECEF) coordinates and geodetic coordinates? I've computed an angle of elevation from one object to another in 3D space in ECEF using $s = (x_1, y_1, z_1)$ $r = (x_2, y_2, z_2)$ Now, take $rx = r \cdot r = |r|^2$ $ry = s \cdot s = |s|^2$ $v = \frac{r \cdot s}{\sqrt{rx \cdot ry}}$ So $v = cos(\theta)$ The angle of elevation from $r$ to $s$ is then $90 - arccos(\theta)$. Is this correct? I'm getting a different result from the accepted answer. The interpretation of $r$ and $s$ are an observer and a satellite orbiting the earth so the desired elevation is the angle above the horizon.

Of course the angle of elevation is different. Computing the angle of elevation requires a local up vector since not every point on earth has the same up direction.