blender gis produced mesh not smooth (not expected)

[sugizo]

steps

• web geodata > basemap (mount everest nepal)
• web geodata > get elevatoin > srtm
• file > export > stl
• convert to *.off to make it smaller size
• open *.off with openscad

marine_geo_gmrt

opentopography_srtm_90

expected result
here is comparison mesh what saga gis produced
steps

• open geo tiff (mount everest nepal) as grid
• create tin from grid
• export tin to stl
• convert to *.off
• open with openscad
  

question
how to make smooth mesh elevation using blender gis

best regards