[mkgmap-dev] length () in relations file

Thu Feb 14 17:10:01 GMT 2013

I'm experimenting a bit with the length() function in the polygons file,
but the results are a bit unexpected.

In my polygon style rule I have 
natural=water & length()>10000 [0x3e resolution 16]

I would expect that mkgmap draws the whole relation of the Wolderwijd: http://www.openstreetmap.org/browse/relation/1204374
The total length of the relation is 33,79 km, see http://ra.osmsurround.org/analyzeRelation?relationId=1204374&_noCache=on
The outer way is only one big way, http://www.openstreetmap.org/browse/way/80129565

But mkgmap draws only half of the lake, see length10km.jpg
If I make natural=water & length()>5000 [0x3e resolution 16] it is a bit better, but still incomplete.

Now this isnt a big issue, because I can use continue for higher zoomlevels, like
natural=water & length()>10000 [0x3e resolution 16-17 continue]
natural=water & length()>5000 [0x3e resolution 18-19 continue]
etc

Just wondering why the polygon isn't rendered completely (if I zoom in, the polygon is still the same edgy looking)

Wanmil wrote:
> It might be possible. The problem to be solved is that the garmin map
> geometry is not rectangular. So at the moment I don't know how the
> area
> size of a polygon can be calculated in a metric unit.
> 
> WanMil
> 
> > Can something like the length function also be implemented for
> > polygons to render big lakes earlier?
> > For example
> > natural=water & area() > 10 [0x3c resolution 16]
> > natural=water [0x3c resolution 18]
> >
> > (gmaptool shows this area in sq km)
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