I have created a displacement map from two pairs of Descending SAR images for an AOI. I have single pixel gives the amount of displacement with minus or plus sign.
I do not have any stable reference point from GNSS instrument in the AOI at present time, but I only know some areas have not been moved or displaced. I chose a point from that area and subtracted from the whole phase map.
In this case, without visiting the site, how I know the area of subsidence from uplift?
Many thanks in advance
Thanks for your swift reply, I have read this post before, but how I know the displacement going towards the sensor or getting far from it ? If I know that I know how to judge but in my case firstly, I don’t have any ground observation from GNSS device and I have not been to the AOT. Secondly, I only have displacement value with sign (+ or -). for example, the phase pixel reads (-0.05 m) and in another pixel reads (+0.07m)…
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.
Dear Fakhri, Thanks for your reply back on me.
Does your first way apply on my case or not as I am almost lost to judge on my LOS displacement map. I have attached a screenshot of my AOI with LOS displacement map and I put the a small area in a red circle with its value on the left hand side of the screenshot.
The engineering staff claims a subsidence of 60 cm by GNSS techniques, however, the SAR interferometry shows only a few cm(s) downlift (in my opinion). I am so confused, I think it is subsidence but not sure in the meantime!
The important thing to you from my point of view is, this area is subjected to the subsidence in ultimately this sign - refers to subsidence, the second thing is, I don’t know what kind of approach do you follow? and what is the goal of your study?
So identify the approach and the goal of your study and therefore, choose the technique you’d like to implement.
The differences of tools and date and method could give a different in the measurement results, that is all what I could say, because I haven’t clue to the details of your study.