[OSM-dev] Eurasian Coastline and the 180 meridian

Dirk-Lüder Kreie osm-list at deelkar.net
Tue Nov 13 07:18:12 GMT 2007


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If we want to have the coastlines as closed entities we need to
implement some sort of support for crossing the +-180° meridian,
otherwise areas crossing over this meridian will "wrap" around the other
side of the world and not close up correctly.
Maybe one can define a maximum "segment" length (not the former segment,
but the part of a way between 2 consecutive nodes) in *degrees*, as
opposed to meters/kilometers, that would ensure the way is continued on
the "shortest" way on the earth, e.g. make it so that you can't put two
nodes more than e.g. 90° or 179.99° apart lest it become ambiguous which
way the connection runs around the world, and have this independently
for longitude and latitude.
Apart from implementing said limit, the api and/or the tools managing
the data must be made aware that -180 is the same as 180, maybe by
"cheating" (allowing numbers like 185°, automatically mapping to -175°
or somesuch).

- --

Dirk-Lüder "Deelkar" Kreie
Bremen - 53.0952°N 8.8652°E

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