Sometimes I think a blog post on this is a bit silly – BUT – given the number of people popping up as of late asking about QGIS let’s do it.
QGIS has a field calculator. You can update fields with text or numbers. In my case (since I’m in the US and we love feet) I do a lot of things in Acres or Square Miles. 
Easy? Yes. It’s pretty easy. With my move into PostGIS, triggers have been my friend for a lot of distance/area measurements. This morning I had some data I was building outside of postgis and decided to jump in and calculate the area. I did. It was wrong. Way wrong. I forgot something!
There was a problem a while back with area. It was fixed. Part of the fix allows you to set up your preferred units going into a project. As part of a test I had just wiped my install of QGIS and reloaded – and I never set it back up again. So – if you are new to QGIS and are getting funny lengths or areas and have no idea why here is what you can do to relieve some pain and suffering.
- If you want to set up Preferred Units for specific project, Click on Project -> Project Properties.
- Set your Measurements. I usually go with None for Ellipsoid and Feet and Square Feet for units.
BUT I WANT IT TO BE PERMANENT and not just for one project.
- Open Settings -> Options
- Go to Map Tools
Of course there you have slightly different options as the ellipsoid isn’t mentioned. Except once I set it for none under project properties it always stays none.
Anyway – I know it’s not that exciting. Except for the number of people starting to look for alternatives to their current commercial software. It’s very exciting. So hopefully you find this out on the internet and it helps you out.
Enjoy calculating your area on this earth.
