[gdal-dev] GDAL / PROJ.4 Transformation (cs2cs) - several results by PROJ.4-Versions (DHDN/GK2 => ETRS89/UTM32)

[Gregor Fikoczek]

Hi list,

i am using the PROJ.4 (cs2cs, GDAL/OGR, UMN MapServer) for transformation
from CS to CS.

start-point (DHDN / GK 2 => epsg:31466)
5216100002;2552401,862;5616707,524

correct destination-point (ETRS89 / UTM 32 => epsg:25832)
32340408.033  5617072.487


example:
cs2cs +init=epsg:31466 +to +init=epsg:25832
 2552401.862 5616707.524

-----------------
Result with PROJ.4 version 4.5.0:
340411,268580576754175;5617068,431440304964781
=> difference to the correct destination point in ETRS89: ~ 5 m
=> fine

Result with PROJ.4 version 4.6 and 4.6.1:
340463.83       5617207.67
=> not so fine / wrong
=> difference to the correct destination point in ETRS89: > 100m
----------------

====> Why the difference in PROJ.4 Version 4.6 and 4.6.1 is the much?

epsg-FILE:
---
# ETRS89 / UTM zone 32N
<25832> +proj=utm +zone=32 +ellps=GRS80 +units=m +no_defs  <>
# DHDN / Gauss-Kruger zone 2
<31466> +proj=tmerc +lat_0=0 +lon_0=6 +k=1 +x_0=2500000 +y_0=0
+ellps=bessel +datum=potsdam +units=m +no_defs  <>
---


###############

When i modified the epsg file like this (add parameter +datum=WGS84 to
EPSG:25832):

from
# ETRS89 / UTM zone 32N
<25832> +proj=utm +zone=32 +ellps=GRS80 +units=m +no_defs  <>

to
# ETRS89 / UTM zone 32N
<25832> +proj=utm +zone=32 +ellps=GRS80 +datum=WGS84 +units=m +no_defs  <>

... the result is as expected and equal like by the PROJ.4 Version 4.5.0.

---
cs2cs +init=epsg:31466 +to +init=epsg:25832
2552401.862 5616707.524
Result:
 340411.27      5617068.43
==> fine
---

So is there a difference between PROJ.4-Versions (Version > 4.5 needs
+datum-Parameter?) or am i doing something wrong?


Best Regards,
Greg


-- 
Mit freundlichen Grüßen / Kind regards

Gregor Fikoczek



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