But this is not the case, despite of the master image, generally suppose that the ground on the zero level any movement towards S. It is uplif and away it is subsidence, this is closest to the fact as well,
It could be calculated in to two ways,
The first way as I explained, So - means subsidence and + means uplif,
The opposite way is , the ground movement calculates according of it distance from satellite, in this case away from satellite it is subsidence and it has + sign , towards satellites it is uplif and it has - sign.