You can either use the profile plot to investigate the backscatter along a digitized line or the histogram tool to investigate the mean backscatter values within a digitized polygon (select ROI mask).
We tried Time-series analysis. We could extract back-scatter co-efficient values in csv formats.
Few of the challenges we are facing is
Time series analysis takes only point data as pins. As co-efficient values are to that point, We are unable to get back-scatter values for polygon data. - Is it possible to import polygons directly and extract mean back-scatter value of the plots?
How good it is to do work with SNAP software when we are dealing with thousands of polygon data?
Actually we are dealing with Agriculture project, where we are suppose to give plot wise health status of the crop from SAR data. We have crop grown information available with us. - What is the right way to analyse and give crop health status?
Kindly suggest on these lines and help us to work towards it.
Yes, you simply import them as described here: Removing land by masking
I don’t know the performance limits of SNAP if you have large amounts of polygons. Do you want to have a plot for each of these thousands of polygons? Can you aggregate them by crop type (dissolve in a GIS)?
I would say, pin points are enough to get an information on vegetation health (NDVI) over a couple of growing seasons. If you can include polygons, even better.
When we tried to extract back- scatter value in time-series analysis its not reading any data imported in as vector layer. I have attached the screenshot below.
Ok… If I have to put the question in different way…
I have export back-scatter co-efficient as csv option available only in Time series analysis. Time series analysis takes inputs from Pin manager. Pin manager has only option to import/create point data.
Is there any other way to give input as polygon to time-series analysis as i need to export co-efficient values? or any other tool is used to export back-scatter values (not as a graph, actual values) .
@ABraun We got zonal statistics - (Mean) using QGIS but the values are in decimals like 0.0210, 0.0328… whereas we used to get -20, -15 back-scatter values form SNAP software. Why is this difference? We used Sigma0VH image. Are we missing anything?
db images are probably virtual only. You see this indicated by the v in the symbol of each band. Right-click your db images > convert band. Then File > Save product. They will then be physically written in your data folder as well and are available for use in QGIS.
this is caused by resampling because both rasters need to be aligned to a common pixel spacing. Use Nearest Neighbor resampling instead of Bilinear if you want to maintain the original pixel values.
resampling always slightly changes the values, unless you select nearest neighbor.
Your graph looks fine but I wonder why you reproject the image while you can define a coordinate reference system in the terrain correction step already.