Ships and AIS data


I am currently generating an AIS data correlation algorithm with the detections made on Sentinel 1 GRD products.
I am finding that in areas near the coast the positions coincide but in offshore areas the distance between the AIS tracking and the detections they go up to 600 meters or more.

I have tried different terrain correction models using the GPT command line and the results between them are very similar. I have also used different DEMs such as SRTM 1Sec HGT or ASTER 1sec GDEM but the results are more or less the same, especially in the coastal zone.

I know that normally for water areas, DEMs usually have heights of 0 or nodata, and take different elevations depending on the geoid, ellipsoid or distances between them.

Can I assume that it is normal for this to occur in deep sea?

Thanks :slight_smile: