From teljeurc@tcd.ie Thu May 6 12:22:43 1999 Received: from mxu1.u.washington.edu (mxu1.u.washington.edu [140.142.32.8]) by lists.u.washington.edu (8.9.3+UW99.02/8.9.3+UW99.01) with ESMTP id MAA33816 for ; Thu, 6 May 1999 12:22:42 -0700 Received: from dux4.tcd.ie (dux4.tcd.ie [134.226.1.194]) by mxu1.u.washington.edu (8.9.3+UW99.02/8.9.3+UW99.01) with ESMTP id MAA30208 for ; Thu, 6 May 1999 12:22:41 -0700 Received: from [134.226.184.50] (smd050.smd.tcd.ie [134.226.184.50]) by dux4.tcd.ie (8.9.3/8.9.3) with ESMTP id UAA22085 for ; Thu, 6 May 1999 20:22:40 +0100 (BST) X-Sender: teljeurc@mail.tcd.ie Message-Id: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Date: Thu, 6 May 1999 20:26:18 +0000 To: waphgis@u.washington.edu From: Conor Teljeur Subject: hospital catchments Hi all, About the problem of defining hospital catchment area. I've been doing a lot of reading and investigation into this topic. Having said that I'm still somewhat in the dark exactly how to go about it. One thing is for sure though, and that is that Thiessen polygons are, as far as I can tell, quite meaningless. They merely provide areas using simple geometric calculations. They completely ignore all underlying demographic information and ignore transport networks. The only reason I can see for using them is to give an immediate idea of the possible scale of the catchment area. A very good description of how you might go about defining a hospital catchment is at http://www.un.org/Depts/unsd/demotss/gisrep/gis4/gis4.htm It's well worth a look and might give some good pointers. It also shows the difference between catchments calculated using Theissen polygons and those calculated by more sophisticated methods. [It's all done using IDRISI, by the way.] I hope that's of use, Conor .