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[mkgmap-dev] mapnik TYP, forest and wetland

From Ticker Berkin rwb-mkgmap at jagit.co.uk on Mon Nov 2 17:18:11 GMT 2020


I understand that many users prefer a fixed order of rendering based on
the polygon type, and this is part of the definition of mapnik.txt and
seems to be the 'Garmin' way of doing things.

If there is a consensus that the draworder should be different, then
make it so. I'd think that wetland and forest should be the same as the
other large-area landuse polygons, with priority 2

Option --order-by-decreasing-area removes the need to make any of these
fixed rendering choices but at the cost of an increase in map size and,
possibly, mkgmap execution time. It works for MapSource and BaseCamp
and Garmin devices I've encountered, but not for GPSMapEdit.
If used, it is best to set the draworder for all real polygons to the
same value.

It is a shame that the TYP.txt file has to contain everything
(draworder, translations and object colour/icons). It would be
beneficial it they could separated and the wanted variants of
components supplied to mkgmap.


On Mon, 2020-11-02 at 16:55 +0100, 7770 wrote:
> Hi.
> In the example mapnik.txt TYP file, the draworder of the polygons for
> woods/
> forest 0x50 and wetland 0x51 are given like this:
> [_drawOrder]
> ..
> Type=0x050,3
> ..
> Type=0x051,2
> ..
> [End]
> When compiling a map, this means that wetlands in forests are not
> visible if 
> this TYP is used.
> I tried makling a map using the same draworder
> Type=0x050,2
> Type=0x051,2
> plus using the option --order-by-decreasing-area
> This makes the wetland visible in forests.
> I could not see any negative impacts of this in the areas which i
> checked (a 
> few in Sweden and Norway). Wetlands over other areas seems to work
> fine as 
> well.
> Do you think such a change would be of help or is there a great risk
> that this 
> type of change would impact negatively on the drawing of the maps?
> Regards
> Karl
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