Calibration for multiple sensors

Hello everyone,

I’ve been working on a project that visualizes earth features across time (2000-Present Day), requiring imagery from multiple sensors: Radarsat-1, ENVISAT, and Sentinel-1. I was cautioned that analyzing change using imagery from multiple sensors may not be accurate unless I properly calibrate them to ensure that, for example, Radarsat-1’s imagery won’t be different enough from ENVISAT’s imagery to complicate change analysis from 2000-2010.

I understand that processing data in SNAP entails an essential first step: Radiometric Calibration. Does this step make all the imagery I process from the three sensors comparable? Or is there an additional step in SNAP (or methods used outside of snap) to make these images comparable?

Sorry if this question has a really simple answer. I’m new to working with SAR data. Thank you for your time and any advice you can offer!

If by comparable you mean the pixels values of all three images are in the same range, then yes, calibration will make them comparable.

Thank you for your reply. Indeed I haven’t found any papers using multiple sensors that detail any sort of calibration between sensors beyond the run-of-the-mill SAR processing. I just want to make sure that when I use ENVISAT to detect study features, they won’t be different enough from Radarsat-1 to make my change analysis inaccurate or misleading. My committee member (I’m a grad student) was pretty adamant about ensuring that the sensors are comparable, so I wanted to make absolutely sure that SNAP’s calibration tool does this.

You may want to run Single Product Speckle Filter operator to filter the speckle noise in the images after calibration.