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[mkgmap-dev] DEM format Questions

From Gerd Petermann gpetermann_muenchen at hotmail.com on Mon Nov 13 09:40:03 GMT 2017

Hi Frank,

found a copy+paste bug in the copy constructor for CodingType:
            HunitValue = ct.HunitValue;
            HunitExponent = ct.HunitValue;

Seems to have no effect?


Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Frank Stinner <frank.stinner at leipzig.de>
Gesendet: Freitag, 10. November 2017 13:20:21
An: mkgmap-dev at lists.mkgmap.org.uk
Betreff: Re: [mkgmap-dev] DEM format Questions

Hi Gerd,

we have ever 2 problems: how to calculate the next value and how we have to encoding this value.

#1: If we have not a plateau, then we have a "Standardwert". For the calculation of a "Standardwert" we have to 3 differend cases depend on the value hdiff(n, m-1) = h(n, m) - h(n-1, m) (horizontal difference, see at the end of "Datenberechnung"). max is highest possible value in this 64x64-subtile.

#2: We have to decide, is it "Längencodierung", "Hybride Codierung" or if they are not possible, "Binärcodierung für große Zahlen". But we have no choice, we have to use that kind, that the algorithms say (see "Umschaltung der Codierart"). That do in TileEncoder.cs the class CodingType and the derived classes.

I'm sorry, but TileEncoder.cs is not written for speed or good understanding. It is only for exploring DEM and, in Input2, for showing, what's going on. There is much place for optimizing. ;)


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