[mkgmap-dev] Contour lines with "Artefacts" near a vertical line situated at W0° 00' 00"

Fri Mar 11 16:22:30 GMT 2022

Hi Gerard,
you can check the elevation contour lines by opening the file generated
by your tool in e.g. JOSM (my take some time when the file is large).
Strange distortions are expected at the borders of the whole set of
input files, but not where input files are adjacent to each other.
Your description seems to hint to a bug when crossing the 0°-meridian. I
do not know how srtm2osm reacts there, it might be worth to try it.

Kind regards,
Bernhard

Am 10.03.2022 um 14:15 schrieb Gerard CATTIAUX:
>
> Hello,
>
> After many hours of time to get a correct knowledge of the most
> important tools needed to produce Garmin map, like mkmap, Splitter..
> and plenty of hours to develop my own Styles files for mkgmap, I am
> now able to produce local maps mainly for Fenix 6x or Garmin 66,
> specifically for Trail Running.
>
> That help me also to have a mean to verify immediately all my
> contributions to OSM database.
>
> To have the best results for my personal maps, I use altitude data
> from Sonny.
>
> https://data.europa.eu/data/datasets/dtm-europe?locale=en
>
> For flat part of the country, I generally generate contour lines with
> a 5m space, in lieu of a 10m or 20m space between contours lines.
>
> That choice seems for me a very good choice for as an example "Ile de
> France" (Extended Region around Paris), where max altitude are between
> 150 to 200m.
>
> I recently generate contourlines near La Rochelle in France for a
> local zone called "Poitou-Charentes",
>
> http://download.geofabrik.de/europe/france/poitou-charentes.html
>
> but unfortunately, I have artefacts, that I don't have for example in
> many other regions of France.
>
> These artefacts are also visible for 5m, 10m and 20m space between
> contours lines.
>
> These "artefacts" are described in the pdf files given at this link:
>
> https://drive.google.com/file/d/1uiA51R4Kd_WYsdeTrEtevu2jJ_8aPinH/view?usp=sharing
>
> To generate my contour lines, I use mainly hgt2osm, with hgt files
> from Sonny.
>
> Hgt files in the example :
>
> N46W002.zip
>
> N46W001.zip
>
> N46E000.zip
>
> N45W002.zip
>
> N45W001.zip
>
> N45E000.zip
>
> Command line
>
> hgt2osm -g HGT-AFAIRE --MinorDistance=10
>
> Hgt2Osm, 13.11.2017, FSofT
>
> 64 Bit-OS: ja
>
> Programmodus 64 Bit: ja
>
> MinorDistance: 10
>
> MediumFactor: 5
>
> MajorFactor: 5
>
> HGT-Verzeichnis:         HGT-AFAIRE
>
> Mergefile:
>
> OutputOverwrite: False
>
> Höhenkorrektur: -0.5
>
> MinVerticePoints: 3
>
> MinBoundingbox: 0.0005
>
> Douglas-Peucker: 0.04
>
> 1. OSM-ID: -1
>
> mit OSMBound: False
>
> mit OSMBounds: True
>
> mit OSMTimestamp: True
>
> mit OSMVersion:          1
>
> mit OSMVisible:          False
>
> max. Punktanzahl je Weg: 500
>
> mit 'contour_ext'-Tag: True
>
> At first sight, it seems that all these artefacts begin just near a
> vertical line situated at W0° 00' 00" / E0° 00' 00"
>
> Any ideas to helps me to solve the problem?
>
> Many thanks
>
> Regards
>
> Gerard Cattiaux
>

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