What is most correct? Warping the DEM before TC or warping the final Sigma0?

Hi guys,

I was wondering what would be most correct for calculating Sigma0 from GRD products. In my opinion, there’s two options that differ in their terrain correction step. Using SRTM 1sec HGT, which is delivered in WGS84, you can:

  • specify map projection in the terrain correction tool; if I want the final result in UTM31, I can specify it here and I guess the tool then warps the DEM to UTM31 using bilinear resampling, and then the terrain correction is applied based on the warped DEM
  • You can also keep the map projection in the terrain correction to the default WGS84, so no DEM warping is taking place. The Sigma0 is terrain corrected based on WGS84 coordinates. The final result can be reprojected to UTM31, so you’re effectively warping Sigma0

My question is, what is most correct here? Or do I see differences which do not exist?