Hi Lambertus, thanks again. I want to solve this problem: In mkgmap we have to calculate the great-circle distance very often, as well as the cross track error. We need the values for all kinds of algos (nearest point, DP-Filter, WrongAngleFixer etc.), not just for the img itself. Up to now we use those formulas which are fastest, but as we saw they do not always work. So I want to find a simple algo to decide whether the fast formula is good enough. Always using the highest precision would slow down mkgmap by ~30 %. Gerd Lambertus wrote
I'm not sure if it is of any help, but with http://yournavigation.org (which also uses OSM) you can specify which distance algorithm to use. It uses this PHP class for the calculations: https://github.com/treffynnon/Geographic-Calculations-in-PHP
Available methods: Vincenty Simplified great circle Haversine Cosine
Add a &v= parameter to the request to choose the algorithm: http://wiki.openstreetmap.org/wiki/YOURS#Parameters
/offtopic: I see YOURS should be upgraded with the new class...
On 31/07/2014 18:21, Andrzej Popowski wrote:
Hi Gerd,
I have looked at your example file in QGIS and Global Mapper and they show distance like JOSM. I don't know why there is so big difference. My guess is that it could be caused by spherical versus ellipsoidal model of the Earth. Maybe you could test algorithms based on Vincenty's formulae? See for example:
http://www.gavaghan.org/blog/free-source-code/geodesy-library-vincentys-form...
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