Re: [Qgis-user] Projecting a Vector layer into another CRS

Thu, 01 Mar 2012 11:58:58 -0800

On 01/03/2012 14:09, [email protected] wrote:

Hello,

I have worked with  ArcGIS before as a part of my course. In ArcGIS we used to carry out Projection of vector layer in WGS 84 to Polyconic projection with a custom central meridian using the Project Tool from the ArcToolbox. And that is saved as a seperate feature in the mdb.

I have been trying to redo all my ArcGIS experiments in QGIS to test the functionality. But I couldn't find out how to do this re-projection. I am using Spatialite in place of the mdb. So It would be better if the resultant is also within the spatialite DB. But the CRS of the entire DB has been preset as WGS 84 during creation. So, how can this be done? 


In QGIS you use the "Save As..."  option (right click on the layer in the TOC) then choose a different CRS. You can save the new, reprojected, layer as a shapefile, or several other formats.

But if you're using spatialite, why not reproject right in the database, using the ST_Transform() function?

I'd create a new table, duplicating the columns from the original (except the Geometry- that you do with AddGeometryColumn(). Then:

SELECT AddGeometryColumn(

    'new_table', 'Geometry', <new epsg code>,<feature type>,'XY');

INSERT INTO new_table (column1, column2,..., Geometry)

    SELECT column1, column2,...,ST_Transform(Geometry, <new epsg code>)

    FROM old_table;


HTH,

Micha

--
Regards
Arunmozhi
Twitter: @tecoholic
Website: http://arunmozhi.in
IRC Nick: teco


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