Note on void filling method in SEAMCAT
- Zeljko Tabakovic
Global SRTM 1-Aec Sec data are not void filled in regions outside the United States. In that respect some tiles contain voids where height data is not defined1.
According to the US Geological Society2,
“SRTM Void Filled elevation data are the result of additional processing to address areas of missing data or voids in the SRTM Non-Void Filled collection. The voids occur in areas where the initial processing did not meet quality specifications. Since SRTM data are one of the most widely used elevation data sources, the NGA filled the voids using interpolation algorithms in conjunction with other sources of elevation data. The resolution for SRTM Void Filled data is 1 arc-second for the United States and 3 arc-seconds for global coverage.”
Voids shown with red colour in one tile
To avoid presenting voids in the extracted profile, SEAMCAT uses method to fill the void data in the profile with the last “valid height”. Note is added to the Terrain profile tool and PMP explaining this method.
1 It is observed that voids in general occurs in mountainous areas where there are big changes in height in short distance or water surfaces.