[Qgis-user] On the fly projection

[Richard Duivenvoorde]

Siki Zoltan wrote:
> I have trouble with on the fly projection from epsg:4326 to epsg:23700.
> When I create a custom projection and test it in QGIS custom projection
> window I get the correct values
> E.g 47d 19d -> 183979.50 646390.96
> parameters: +proj=somerc +lat_0=47.14439372222222
> +lon_0=19.04857177777778 +k_0=0.99993 +x_0=650000 +y_0=200000
> +ellps=GRS67 +towgs84=52.17,-71.82,-14.9,0,0,0,0 +units=m +no_defs
> 
> But when I have the same point in a shape file and turning on on the fly
> reprojection with EPSG:23700,
> I get 646306.05 183949.62, and it is the same if I ommit the towgs84
> parameters, more than 90 meters difference.
> Where can I change the projection definition permanently in QGIS?
> I changed the epsg file of proj but it doesn't help.
> 
> Trying it on QGIS 1.6 Linux and XP, I get the same result.

Hi,

the projection information / proj4-strings for qgis are stored in srs.db
(<QGIS>/share/qgis/resources/srs.db in my setup) which is a sqlite
database (viewable/editable with eg a firefox plugin:
https://addons.mozilla.org/en-US/firefox/addon/sqlite-manager/)
You could edit the record there for the epsg:23700 record. But this
means that with a new install you loose your proj-string edits.

The preferred way is actually to add a 'Custom CRS' (file menu Edit) and
add your definition of the proj-string and name it 'My23700' crs or
something like that.
Then the definition ends up in qgis.db (the user settings sqlite db) in
your .qgis home. And it will survive new projects and your qgis-updates
in the future.

Regards,

Richard Duivenvoorde