improve performance for areas where no srtm data is available
improve performance for areas where no srtm data is available

probonopd/marble,oberluz/marble,tucnak/marble,AndreiDuma/marble,David-Gil/marble-dev,tzapzoor/marble,rku/marble,quannt24/marble,quannt24/marble,rku/marble,tzapzoor/marble,David-Gil/marble-dev,tzapzoor/marble,Earthwings/marble,utkuaydin/marble,quannt24/marble,Earthwings/marble,oberluz/marble,David-Gil/marble-dev,David-Gil/marble-dev,AndreiDuma/marble,David-Gil/marble-dev,tzapzoor/marble,tzapzoor/marble,utkuaydin/marble,quannt24/marble,utkuaydin/marble,probonopd/marble,tucnak/marble,Earthwings/marble,adraghici/marble,rku/marble,Earthwings/marble,probonopd/marble,oberluz/marble,rku/marble,tucnak/marble,AndreiDuma/marble,utkuaydin/marble,AndreiDuma/marble,AndreiDuma/marble,quannt24/marble,tucnak/marble,probonopd/marble,tucnak/marble,rku/marble,tzapzoor/marble,oberluz/marble,Earthwings/marble,tucnak/marble,tucnak/marble,adraghici/marble,utkuaydin/marble,AndreiDuma/marble,Earthwings/marble,adraghici/marble,adraghici/marble,probonopd/marble,quannt24/marble,rku/marble,tzapzoor/marble,utkuaydin/marble,probonopd/marble,probonopd/marble,oberluz/marble,adraghici/marble,adraghici/marble,David-Gil/marble-dev,tzapzoor/marble,quannt24/marble,oberluz/marble