artemp/trac2github — Issue #840: custom wgs84 -> merc proj_transform
Author: artemp
Created: 2011-10-09 20:52:49+00:00
State: open
Labels: Core_Library

We could write native, fast transforms for very common source/dest projection transformations not requiring datum shifting.

Artem and I have discussed having special keywords for projections like `mapnik::sphericalmercator` and `mapnik::wgs84`, that could make it quite easy to detect or trigger these built in transforms. Native transforms would avoid using proj4 (and incurring proj4's file i/o (for epsg lookups) and potential mutexes (in <= proj 4.7)). In addition special builds of applications using mapnik (like on mobile devices) that do not need fancy projections support could even then allow proj4 to be dropped as a dependency.