I am new to QGIS and working with QGIS 1.7.3 version, I have my all layers in WGS 84 CRS but even though they are not overlapping to each other, What should I do ?
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My first guess would be that the spatial references are not correct or may be missing. If you have a layer that you know is correct (i.e. other layers overlap) then take an incorrect layer and try to reproject using the coordinate system from a correct layer. This walk-through may be of some use to you.