SNAP Projection accuracy vs. optical

I have a technical question regarding the projection alignment and accuracy. I used Lidar DEM for orthorectifying Radarsat-2 registered in WGS84, UTM projection in SNAP. Meanwhile, I have also SPOT optical images for the same area (already ortorectified in in PCI Geomatica in the same projection above) .

Now I see that there is an offset about 50 m (10 pixels of 5m) which is significant between SAR and optical. Now I wonder what did go wrong! For the SAR processing all was done in SNAP TC. Even SAR image still has some offset on Google Earth which is less than that of optical though.

Any comment is appreciated!


How accurate is the LIDAR you are using as a DEM in terms of both it’s georeferencing and height? It’s all about the geometry. How far will the SAR penetrate and where is the actual return compared to where the LIDAR surface return is.

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