[mkgmap-dev] length () in relations file

Thu Feb 14 17:46:43 GMT 2013

Hi Minko,

I assume the polygon is cut into smaller pieces because it has inner
polygons. The length() function
sees only the parts after cutting.

Gerd

Minko-2 wrote
> 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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> 
> lenght10km.jpg (72K)
> &lt;http://gis.19327.n5.nabble.com/attachment/5749426/0/lenght10km.jpg&gt;
> length5km.jpg (71K)
> &lt;http://gis.19327.n5.nabble.com/attachment/5749426/1/length5km.jpg&gt;

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