I am a very definite QGIS newbie. I have been creating a map using files that had been used in ArcGis. Each time I wanted to add a new vector layer I opened an .shp file and specified CRS as WGS 84. The resulting layers look fine but when I try to use the "measuring tool" to measure line length I get an error message as follows:
This map is defined with a geographic coordinate system (latitude/longitude) but the map extents suggests that it is actually a projected coordinate system (e.g., Mercator). If so, the results from line or area measurements will be incorrect. To fix this, explicitly set an appropriate map coordinate system using the Settings:Project Properties menu.
any advice on how I might determine what might be an "appropriate map coordinate system" ?
I am also wondering if I should have also opened the corresponding .shx, .sbx, .dbf, .sbn and .qix files also ?