[mkgmap-dev] Incorrect compilation of grid lines

Mon Jul 28 06:25:03 BST 2014

Hi Felix,

see 
http://gis.19327.n5.nabble.com/Patch-v1-detect-cases-where-Herons-formula-is-failing-in-3D-tp5812773.html

please let me know if the patched verrsion causes any problems.

The only expected effect of the patch is that fewer points are removed
from the original data. On normal OSM data, the effect is minimal.

I tried it with normal OSM data and some contourlines. For data
in Australia I see small changes at low resolutions (<=15) for shorelines,
but I can't say which result is worse, as both versions are a mess.

Gerd

> Date: Fri, 25 Jul 2014 11:24:44 +0200
> From: extremecarver at gmail.com
> To: mkgmap-dev at lists.mkgmap.org.uk
> Subject: Re: [mkgmap-dev] Incorrect compilation of grid lines
> 
> Hi Gerd,
> 
> the only thing I am afraid about is broken contourlines data (due to 
> errors or missing data). There you quite often end up with long straight 
> lines. So the patch shouldn't make such errors even worse - I long even 
> hoped that mkgmap could have a function/filter to delete all long lines 
> - say straight over 5km without intersection, because I don't think that 
> such long straight lines exist in OSM data (except ferry lines, power 
> lines, railways and highway=motorway/trunk)
> 
> 
> So maybe better not detect such a problem automatically, but add a 
> filter for the style-file where you could switch off douglas peucker 
> especially
> e.g.: gridlines=yes [0x* nodouglaspeucker]
> On 25.07.2014 11:15, Gerd Petermann wrote:
> > a simple patch that tries to detect that the formula doesn't work.
> > I just have to decide what to do in that case, typically it is better 
> > to keep the point, so
> > img size might increase.
> 
> -- 
> keep on biking and discovering new trails
> 
> Felix
> openmtbmap.org & www.velomap.org
> 
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