I've a csv file that includes weather stations locations (x,y,z) and precipitation values. I loaded the file by using add delimited text and then converted it into a point shapefile WS84. By using the interpolation plugin I managed to create the different rainfall zones using pseudocolor and later I extracted the contour. However, as I have z values for elevation I'd like to take this into consideration. The interpolation plugin includes the option to select z-Coordinate to load elevation points but I cannot select it. When I open the plugin without any layer loaded the check box works fine, but when the layer is present is not possible to select the check box. The values of elevation column (z) are in mm. Am I missing anything ?
Qgis 1.8.0, interpolation plugin loaded from the repository, running Windows Vista.
Addition: I believe the answer is below. z data must be within the shapefile not as a feature. Thanks Bernd V!
"Also note that you can use the z-coordinate for the interpolation. This is the elevation of your data that is stored within the geometry itself and not in an attribute column. This is only possible if your GIS data is in 3 dimensions." in gistutor.com/quantum-gis/20-intermediate-quantum-gis-tutorials/… . So it seems you need to generate "real" 3D-data first, but this is a blank spot for me, sorry. – Bernd V