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

We have multiple populations of patients spread out over geographic distances. For each population, we want users to easily define non-overlapping polygons. The outer borders are likely to be U.S County boundaries, if that makes any difference.

Essentially, I'd like for users to visually build groups of non-overlapping polygons and have the application provide us with sets of coordinates for each polygon. I would then be using the data in Google Maps. We currently have a method to identify patient's location by lat/long, using Google Maps API if the user needs to approximate the location.

Web-based software is preferred, but I'd consider a desktop package if the interface was easy enough for our users with minimal training.

share|improve this question
How do you currently store the patient data? It sounds like you need some type of spatial database. – djq Sep 11 '12 at 20:28
Are you talking about building something like a Voronoi diagram – RyanDalton Sep 11 '12 at 23:41
@celenius: updated the post to state that we're storing location by latitude/longitude. – Jeff Bauer Sep 12 '12 at 0:44
@RyanDalton: A Voronoi diagram may be a mathematical explanation of what I'm trying to achieve, but from a user/use case perspective I'm looking for a means of constructing non-overlapping polygons and capturing the data as lat/long points. – Jeff Bauer Sep 12 '12 at 0:52
up vote 1 down vote accepted

One approach could be to use OpenLayers to enable users to draw polygons onscreen, and then to store these polygons in a postgresql/postigs database, transferring the data using the WFS-T protocol. I would avoid using the Google API directly as it does not easily facilitate analysis.

I don't quite understand what you mean by 'non-overlapping polygons'; do you want users not to draw over existing polygons?

share|improve this answer
Correct, I want adjoining polygons (polygons where the edges join), but do not want them placed over existing polygons. – Jeff Bauer Sep 12 '12 at 15:45
That sounds like it might be easiest to check on the server side. A user can draw a polygon and then it could be submitted, then using PostGIS, the function ST_Intersect could see if there is any overlap. – djq Sep 12 '12 at 15:55
The 'drawing tool' is what I'm looking for. We're currently investigating OpenLayers to see if it can fit the bill. – Jeff Bauer Sep 13 '12 at 1:54
You've probably seen this: – djq Sep 13 '12 at 2:58

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.