[mkgmap-dev] help neededFrom GerdP gpetermann_muenchen at hotmail.com on Fri Aug 1 15:12:38 BST 2014
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-formula-java/ >> >> >> http://geographiclib.sourceforge.net/html/java/ >> > > _______________________________________________ > mkgmap-dev mailing list > mkgmap-dev at .org > http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev -- View this message in context: http://gis.19327.n5.nabble.com/help-needed-tp5813164p5813404.html Sent from the Mkgmap Development mailing list archive at Nabble.com.
- Previous message: [mkgmap-dev] help needed
- Next message: [mkgmap-dev] help needed
- Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]
More information about the mkgmap-dev mailing list