From my viewings, if an aircraft 'hits' the polar diagram on the side, it very often will not move it. More often than not, the aircraft will have to 'hit' the polar diagram on the actual tip of the spike in order to extend it. Also, if an aircraft is at low altitude it will be picked up on the map but will not cause any movement on the polar diagram by, most likely, timing out before it reaches it. Therefore the higher altitude of the aircraft flight level plus a direct 'hit' on the polar diagram the better.