[morcheeba]

Two issues to consider:

- GPS positioning is more accurate if the satellites it sees come from a variety of angles (GDOP), so the satellites near the horizon are valuable.

- Aircraft pitch and roll, so a fixed antenna like this would lose precision as it turns to make an approach - just about the worst possible time.

It's difficult to make an antenna with a sharp cutoff to limit the ground vs. above-ground. So, most anti-jammers will use beamforming to cancel out interference in one or more specific directions. So, the null in the antenna moves to follow the interference.

GDOP: https://en.wikipedia.org/wiki/Dilution_of_precision_(navigat...