I am new to QGIS (in GIS actually).
I followed the tutorials on extracting contour lines from DEM (which I downloaded from cgiar.srtm) using QGIS. Everything went well except that there is no contour line with 0 elevation. The contour lines started with the elevation of 10. I checked the DEM file and the minimum value is 0.
How do I set the QGIS so that the resulting contour lines starts with 0 elevation (and that there is a contour line with 0 elevation)?