Hello,

I need to get altitude differences between two products of different dates. Is there any way ? It can be done with GRD products?

Thanks

Hello,

I need to get altitude differences between two products of different dates. Is there any way ? It can be done with GRD products?

Thanks

Do you mean elevation difference at a point on the ground? This should be done with SLCs using InSAR.

Or do you mean the altitude of the satellite? This is in the metadata.

I was referring to elevations difference at a point on the ground.

Thanks

GRD stands for Ground Range Detected product.

The Slant to Ground Range projection is made in the ESA SAR processor (ERS, ASAR and S-1) using a flat earth (ellipsoid) model. There is no DEM used in this step.

There is an extra subtility for S-1 where the processor is using the WGS84 ellipsoid inflated by the mean scene height in range regularly updated in azimuth. The height used can be found in the geolocation grid for example. You can perform bi-linear interpolation to find the height of your point (used in SAR processing) and repeat for the 2nd image

In the case you need the exact height it is more complex.

In order to find the precise height of a point for a data you need to perform a geocoding step using a DEM (e.g. SRTM). You need starting from the timing of a point (azimuth, range) and the orbit state vector to use geocoding based on range-Doppler to find the intersection with the DEM (which then gives the height).

Applying that for two images will give you what you want.