Getting projection from vector layer in QGIS

Question

I am trying to set the projection on a raster to match that of a vector point layer. Thus I need to find out what is the projection of a given layer, to use it in the GDAL.Dataset.SetProjection() so that I can create the GeoTIFF with the appropriate projection.

How do I do that in QGIS using Python?

Another way to put it is: How to get the EPSG for the Layer? — fccoelho, Sep 25 '12 at 11:55
Do you want to reproject the raster to the vector's CRS using Python? Please try to clarify. — underdark, Sep 25 '12 at 12:01
@fccoelho In the python console: iface.activeLayer().crs().postgisSrid() returns only the EPSG code as an integer. — Stefan, Jun 20 '18 at 14:36

score 21 · Accepted Answer · answered Sep 25 '12 at 23:48

Short answer

qgis.utils.iface.activeLayer().crs().authid()
# returns: PyQt4.QtCore.QString(u'EPSG:26913')

Explanation

qgis.utils.iface.activeLayer() returns a reference to the active QgsMapLayer.

QgsMapLayer.crs() returns the crs or QgsCoordinateReferenceSystem for the layer.

QgsCoordinateReferenceSystem.authid() returns the Authority identifier for the crs as a QString.

However, this is assuming there is an active layer, it is of a vector type, and it has a valid crs. You will want to test for validity of those items before committing to reprojecting a raster.

If you are reprojecting, using GDAL.Dataset.SetProjection() will not suffice, since it will only assign a projection and not reproject (warp) the raster to the same as your vector layer.

I ended up using: layer.srs() to get the layer and then srs.epsg to get the EPSG code for the layer. Then, to generate the geotiff: see here: https://github.com/fccoelho/spatialKDE/blob/master/kernel.py in the to_geotiff method. — fccoelho, Sep 29 '12 at 16:23

score 2 · Answer 2 · edited Apr 14 '22 at 05:38

2

You can get the active layer's CRS with:

layer = iface.activeLayer()
lyrCRS = layer.crs().authid() # returns a reference to the active QgsMapLayer
print(lyrCRS)

edited Apr 14 '22 at 05:38

Taras

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answered Oct 18 '17 at 12:25

user107473

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Getting projection from vector layer in QGIS

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