What causes an enemy pilot to appear on the minimap?

While playing Titanfall, one can often gets periodic updates on the positions of enemy pilots by their appearance on the minimap as thick red dots.

Under what conditions can a pilot appear on the minimap?

Does shooting at non-pilot enemies cause an enemy pilot to appear? or is it from a friendly pilot using a radar pulse?

Some levels have spy drones occasionally flying around, do those expose the player's position to the enemy?