QGIS » QGIS Application

My point of view, after giving many training courses, is that the default option should be changed to "prompt for CRS", eventually adding a checkbox in the dialog windows that pops up, to avoid being asked over and over for the reminder of the session.

Why?

a few reasons:

*) common/new qgis users tend to not go and configure "options -> CRS -> coordinate reference system of new layers" to match their needs

*) common/new gis users do have and hard time understand how/when a layer do not have a explicit CRS, examples: a TIFF with worldfile or a Shapefile with no .prj file

*) a few tools, both core and 3rd party plugins, do produce output layers (in memory layers or file based layers) that are usually added to the canvas and given (in their properties) the CRS defined in "use default CRS displayed below" (of the "options -> CRS -> coordinate reference system of new layers" option). If the user do not change this option, it is by default WGS84 and in many cases is obviously wrong, leading to a number of problems (reprojections in the wrong place, layers saved with the wrong CRS, etc.). Exemples: the "cad tools" plugin and the "raster terrain analysis" plugin.