[mkgmap-dev] Draw Order, Precompiled sea and Mapsource

Sun Dec 30 10:21:24 GMT 2012

WanMil,

On 29/12/2012 21:06, WanMil wrote:
> That's ok. Options are ordered and are valid only for the subsequent 
> input file. So if you define the precomp-sea last it is not used for 
> any of the tiles and does not show any sea. I think that's also the 
> explanation for the other variants. 
Understood.
> Mmh, I think I don't understand what you mean with "but not the 
> other". Do you mean ways are shown only for the geographical tile 
> (which I think is the 60923011.osm.pbf) but not for the grid tile? 
> Does the grid tile have ways? 
Yes, it has two perpendicular sets of ways (north-south and east-west), 
with nodes at some of the crossing points.

I think I now understand what is happening:

1. Mapsource loads tiles in ascending order of mapname;
2. Only tiles listed after the pre-compiled sea option have the sea 
incorporated;
3. If a tile having pre-compiled sea is loaded after another tile, it 
will hide features which are in/over the sea on the first tile.

These three rules accurately explain all my results. So the problem is 
with the Mapsource loader, and I can now see how to work round it.

The reason for the difference in compile times is that the GBGrid.osm 
covers a much bigger geographical area than 60923011.osm.pbf, so 
processing the sea takes longer when applied to this tile.

This effect will only be seen when an overlay with features in the sea 
is used. Since the only other common use for overlays of this type that 
I can think of is contours, and contours don't appear over the sea, this 
will not often be a problem.

Thank you very much for your comments, which have helped me to work out 
what is going on.

Regards,

Roger

>> mapname:60000002
>> description: Grid-File
>> input-file: GBGrid.osm
>> precomp-sea=..\resources\sea
>> mapname: 60000001
>> description: GB-Carlisle
>> input-file: 60923011.osm.pbf
>>
>> input-file: ..\resources\style.txt

-- 
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Roger Calvert
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