id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
5399	Swissgrid CH1903 is off by up to 3 meters (does not use data set of local corrections )	bastiK	team	"To calculate CH1903, 2 steps are required:

 (1) WSG84 -> CH1903+  (using a formula)

 (2) CH1903+ -> CH1903  (using a grid / triangulation file)

Step (1) if fully implemented. However step (2) is missing. It introduces corrections of up to 3 meters (plus false easting/northing of 2000000/1000000) and accounts for the historical deviations from the modern system.

To fix this, we could:
 * Use the ""official"" triangulation file and FINELTRA algorithm.
 * Use the NTv2 grid file provided by swisstopo. This is an approximation, but should be in general good enough for osm use.

Link:
http://www.swisstopo.admin.ch/internet/swisstopo/en/home/products/software/products/chenyx06.html"	defect	closed	normal	17.03	Core	latest	fixed	projection swiss unit test ntv2 grid	sbrunner stoecker simon04 wiktorn Klumbumbus sebastic