[Proj] truble to translate coordinates from WGS84 to EPSG:31287

[Markus Hetzmannseder]

Hallo,

i have trubles to translate WGS84 coordinates to EPSG:31287. This is 
needed at the Openstreetmap Projekt for the correct projection of OSM-data 
to the austrian geoimage.at WMS-service. For the OSM-editor JOSM there is 
a plugin epsg31287, that should do the job and in its calculations it is 
based on proj. That plugin is based an proj is working, its not working 
really correct. It is producing a shift of about 30 metre and that shift 
is only local, in other regions of austria the shift has a different 
length and different direction.

For debugging that shift i started to use proj directly, and it is 
producing the same shift in its calculations like the JOSM-plugin.


The correct proj arguments for EPSG31287 should be:
+proj=lcc +lat_1=49 +lat_2=46 +lat_0=47.5 +lon_0=13.33333333333333 
+x_0=400000 +y_0=400000 +ellps=bessel 
+towgs84=577.326,90.129,463.919,5.137,1.474,5.297,2.4232 
+units=m +no_defs

For my reference i use the coordinate translation service of geoland.at 
(http://www.geoland.at/geolandcoord/eingabe.aspx)

The results are for some example points:

WGS84                    proj-EPSG31287               geoland.at-EPSG31287
14.2833092 48.3098392    470439.28	490437.40     470507.17  490503.03
16.371345 48.211996      625637.33	483542.58     625724.57  483601.75
9.747076 47.503042       130035.17	406569.01     130056.24  406637.26

The geoland.at projection is, as far i know, the real projection the 
WMS-service (http://wms.geoimage.at) is using.


Any hints where the difference could be come from?

thx a lot
Markus Hetzmannseder