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I am pretty new in QGis and I encounter the following problem.

I have 2 rasters, let's say, "cadaster" and "tranchot". The raster "tranchot" was georeferenced from the raster "cadaster" with QGis. After the georeferencing, QGis shows the 2 rasters perfectly superimposed and built on the same projection.

Today, I want again to superimpose this 2 rasters but "tranchot" looks like a thumbnail in the corner of "cadaster". From the metadata, the pixel makes 0.1143 meter for "cadaster" and 0.02831 meter for "tranchot".

Probably there is an handling to be done in QGIS to superimpose these two rasters, probably simple, yes, but which one ?

In the future, I'll need to compare vectors from "cadaster" with the raster "tranchot". Is there a mean to make rasters and vectors superimposable permanently ?

Many thanks in advance for your help

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1 Answer

Most probably you have not enabled on-the-fly-projection in Settings/Project Settings, Tab: CRS

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In Settings/Options/CRS Tab/, =Enable "on the fly" reprojection by default= is enabled. Despite this, I have a thumbnail instead of a surimposed raster. –  primavera49 Aug 21 '12 at 14:01
    
The two raster layers still have the same layer CRS? You can try to install Openlayers plugin from sourcepole repository, and look which of your rasters is too small, when overlayed on Openstreetmap or Google background. –  Andre Joost Aug 21 '12 at 14:41
    
The two rasters have the same CRS (from EPSG 28992). The two are historical maps. On the safe side, I had saved as project the surimposition given by QGis after georeferencing and as it, I can see correctly the two maps. –  primavera49 Aug 21 '12 at 15:43
    
I installed OpenLayers but it's probable not the problem because on its current state, QGis is able to show the 2 maps correctly. There is a big difference in the metadata, the meter/pixel value. Concerning OpenStreetMap and Google Background, I know nothing about it... –  primavera49 Aug 21 '12 at 15:53
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