[OSM-dev] Earth radius

Stadin, Benjamin Benjamin.Stadin at heidelberg-mobil.com
Sat Jun 18 09:39:54 UTC 2016


I indeed need to express distances in meters. This is a sinusoidal grid
with 
Varying cell resolutions, matching the length of web mercator tiles at the
equator. 
I could use any value greater or equal to the defined sphere radius, but
not smaller. 
To be consistent, it should be equal.

Ben



Am 18.06.16, 02:50 schrieb "Dirk-Lüder Kreie" unter <osm-list at deelkar.net>:

>Am 17.06.2016 um 21:39 schrieb Stadin, Benjamin:
>> Hi,
>> 
>> I want to double check the earth radius used by OSM and zoom levels is
>> exactly 6372.7982 as said here:
>> http://wiki.openstreetmap.org/wiki/Zoom_levels.
>> 
>> I couldn¹t find this as constant in the sources yet. I¹m creating a new
>> storage system for vector tiles, independent of a projection.
>
>This constand is completely unnecessary for the projection itself unless
>you want to express distances in meters (or any other unit of length),
>since lat and lon are angles from the equator and meridian respectively.
>As long as you don't need a scale you can ignore the radius or set it to
>any arbitrary number (although 6372.7982 km is not a bad choice)
>
>-- 
>
>Dirk-Lüder "Deelkar" Kreie
>Bremen - 53.0901°N 8.7868°E




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