I wonder how SD calculates the "minimum safe altitude". I know that I change in settings "vertical terrain clearance" and "abeam terrain clearance" (+ same for obsructions).

If you like, check this example:
- assuming a flight from the northwest to the southwest of "Millstätter See" (http://en.wikipedia.org/wiki/Millst%C3%A4tter_See)
- surface elevation of the lake is 1929ft
- even if I select for all four above values "0", the calculated MSA is 4300 ft
- with more realistic seetings (1000ft/1nm) I end up with 5000ft MSA to fly over a lake with 1900ft elevation

Why?

I noticed this when planning different transalpine routes: SD's MSA was always minimum 2000-3000ft higher than the MSA on the Swiss ICAO map (e.g. Swiss "skyguide" recommend 7500ft for GAFOR Route No 83 from Bad Ragatz to Biasca - the highest point on this route is 6285ft)

Can anybody explain?

regards
Georg