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[mkgmap-dev] [Patch v1] detect cases where Herons formula is failing in 3D

From Roger Calvert roger at rogercalvert.me.uk on Sat Jul 26 13:51:14 BST 2014


This patched binary for 3316 seems to have solved the problem - thank 
you very much!

As regards the exponent format, I did not know it was there - must be 
something to do with the rounding to 7 figures. There are 9 occurrences 
- all 'E-05'. I will modify the file generator to get rid of them.

Thanks again,


On 26/07/2014 11:15, Gerd Petermann wrote:
> Hi all,
> attached is a patch that addresses the problem described be Roger Calvert:
> http://gis.19327.n5.nabble.com/Incorrect-compilation-of-grid-lines-tp5809502.html
> The problem is caused by the fact that we use a 2D formula for objects 
> which are on
> a spherical surface. In most cases the error is very small and can be 
> ignored, but
> sometimes it isn't. We use the formula to decide whether a point is 
> important or
> not, so I decided that to keep all points where the error is big.
> A better way would be to use a correct formula in that cases, but I am 
> not clever
> enough to code the correct formula  in Java :-(
> @Roger: Please check if the results are ok for you.
> BTW: osmconvert seems to have a problem with some coordinates, e.g.
> <node id='90053000500' lat='54.3788936' lon='1.67E-05' version='1'/>
> is interpreted as
> <node id="90053000500" lat="54.3788936" lon="1.67" version="1"/>
> Don't know if the OSM api allows the exponent format?
> A compiled patched binary for mkgmap can be found here:
> |http://files.mkgmap.org.uk/download/217/mkgmap.jar|
> Gerd
> _______________________________________________
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> mkgmap-dev at lists.mkgmap.org.uk
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Roger Calvert
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