[mkgmap-dev] r4006: 1st alpha version to write DEM data

Thu Dec 21 08:51:29 GMT 2017

Hi Henning,

yes, that matches my findings. So far I found a small difference in the encoding of plateau lenghts
but even when I changed my code to match that of BuildDEMFile I did not see an improvement.
I am now trying to find out why BuildDEMFile sometimes interpolates a different height value.
The values differ by a few cm and thus sometimes mkgmap rounds down while BuildDEMFile rounds up
(or vice versa). I am pretty sure that this is not a problem but it makes it nearly impossible to compare the
resulting bit streams.
Just a matter of time ...

Gerd

________________________________________
Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Henning Scholland <osm at hscholland.de>
Gesendet: Donnerstag, 21. Dezember 2017 00:59:38
An: mkgmap-dev at lists.mkgmap.org.uk
Betreff: Re: [mkgmap-dev] r4006: 1st alpha version to write DEM data

Hi Gerd,
just a brief feedback: Overall it seems to be fine. In MapSource and
Basecamp most of the DEM-Data is displayed. But there a many squares
completely empty (I guess not read at all by Garmin). Of these tiles a
lot are along the coast and nearby lake-area. Maybe this is related to
large areas with no changing elevation. But also there are some
coast-tiles working well. If you need additional information, please let
me know.

Bye Henning

On 21.12.2017 00:36, Gerd Petermann wrote:
> Hi Henning,
>
> please try with r4008 which implements that and also interpolation of hgt values. There seems to be a major bug somewhere in the encoder, sometimes MapSource displays only
> parts of the map and relief looks wrong. I did not yet find out where exactly the problem is. I tried to compare the results from mkgmp with those from BuildDEMFile.
> It seems that mkgmap sometimes calculates different positions because of rounding differences. I tried to do most calculations with integers while
> BuildDEMFile uses doubles. Will try again tomorrow.
>
> Gerd
>
> ________________________________________
> Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Henning Scholland <osm at hscholland.de>
> Gesendet: Mittwoch, 20. Dezember 2017 17:06:25
> An: mkgmap-dev at lists.mkgmap.org.uk
> Betreff: Re: [mkgmap-dev] r4006: 1st alpha version to write DEM data
>
> Hi Gerd,
> it's a great news. I wanted to try it on my map of China. But
> unfortunately failed because of missing files in the sea area between
> Korea and Japan. Maybe it's a good 1st approach to interpret a missing
> file as an area with 0 elevation.
>
> Anyway, thanks for all the research work on DEM!!!
>
> Bye,
> Henning
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