Opened 16 years ago
Last modified 8 years ago
#5399 closed defect
Swissgrild CH1903 is off by up to 3 meters (does not use data set of local corrections ) — at Initial Version
| Reported by: | bastiK | Owned by: | team |
|---|---|---|---|
| Priority: | normal | Milestone: | 17.03 |
| Component: | Core | Version: | latest |
| Keywords: | projection swiss unit test ntv2 grid | Cc: | sbrunner, stoecker, simon04, wiktorn, Klumbumbus, sebastic |
Description
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/topics/survey/lv03-lv95/chenyx06.html
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