Geographic Information Systems Stack Exchange is a question and answer site for cartographers, geographers and GIS professionals. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I've been playing around with the Random Points tool in QGIS to realize stratified random sampling, but I'm running into a problem where I want my strata to be based on a polygon ID, not each individual polygon. In other words: I may have multiple non-contiguous polygons that all represent a single strata, where I want a TOTAL of (e.g.) 10 points randomly distributed among the disconnected polygons, not 10 per polygon. Is there any way to do this? Would a multi-part polygon work, for this?

share|improve this question
Did you tried points in polygon option>? – Arun Sep 6 '13 at 7:28

Using a multi-part polygon does work. Below, a multi-part (blue) and single polygon: Multi-part polygon (blue) and single (white)

Using the random points tool and 20 points per polygon, 20 points are distributed amongst all three blue parts of the first polygon: enter image description here

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.