# How Can we figure out the amount of area of the subsidence and upliftment?

Q1: After generating the displacement map, I want to figure out that, how much area is showing subsidence rate of specific range. How can I calculate it?

Q2: And how is it possible to cut the area out of one or two bursts, because I don’t want area of complete burst?

you can use the mask manager to identify the pixels above a certain threshold
e.g. displacement > 0.4
then you determine the area of the mask. Examples are given here: Landcover classification with Sentinel-1 GRD (page 28 onwards)

I don’t get the second question, please give an example.

1 Like

Q1 is in the wheelhouse of GIS software, so in general you are better off loading the data in your favorite GIS tool (or the freely available QGIS). If you have a large number of files to process, most GIS systems support scripting. Some care is needed to get accurate results with mapped data due to the different surface area of mapped pixels. If you use an equal area projection you only need to determine the area of one pixel. For small regions the difference in areas may be small enough to ignore, but using a GIS package makes it easy for others to closely reproduce your results.

Thank you @ABraun.
If we look at one bursts, sometimes, we want to study smaller region than the region covered by one burst. I want to know how can I cut or crop that portion?

Can you provide me some links which shows the processing of the image in QGIS or any other GIS software?

you can create a spatial subset after debursting the interferogram, explained on page 14 of this tutorial: Sentinel-1 TOPS interferometry

The link provided by @ABraun gives examples for QGIS.

If you aren’t already GIS user you should start with the QGIS tutorials. Two common approaches to measuring areas are: 1) using a raster with a small number of discrete values and an equal-area projection, QGIS has raster tools to give you the total number of pixels for each discrete value, 2) QGIS can convert a raster mask to a shapefile and compute the area of the shapefile.

1 Like