I can't figure out how to make areal calculations (eg. in km2). I have tried the 'field calculator', I have tried the 'measure area' function on the "attributes" toolbar, and i have tried fTools in the "Vector"-menu.
How I do:
- Open Qgis
- Add Google Hybrid Layer (OpenLayers Plugin)
- Find tenniscourt (should be 200-260m2)
- attribute toolbar->measure area - result: 65.060 m² hmm?
- layer->new shapefile layer->polygon, save, "add feature" and drawing polygon. Then field calculator $area - result: 118.48828125
- repeat with new shapefile - result: 4.05503328693158e-08
- vector->geometric tools->export/add geometric columns = another random result
I can't figure out what I am doing wrong! For me it seems like there is some error in the program? I have tried saving the shapefile and opening it again in a "blank" project - same result - and new result every time?