Hi Shane, sorry for the delay, i had no access to the Internet for while.
here is a short definition of the term buffer from http://www.fws.gov/data/IMADS/glossary.htm : buffer - A zone of a specified distance around coverage features. Both constant- and variable-width buffers can be generated for a set of coverage features based on each feature's attribute values. The resulting buffer zones form polygons-areas that are either inside or outside the specified buffer distance from each feature. Buffers are useful for proximity analysis (e.g., find all stream segments within 300 feet of a proposed logging area). In this context you could create a buffer with a distance X and a buffer with a distance Y around the point, and then look for point wicht are in the in the area of (bufferX-bufferY). nico >Could you reply with a URL to what buffers are and how they would be >used in this context? I'm >totally unfamiliar. > > > On 9/9/07, Nico Mandery < nicomandery <at> googlemail.com> wrote: >> Hi Rainer, >> >> You could could use a buffer instead of bounding boxes. >> Just an idea >> >> Nico >> >> Am Sonntag 09 September 2007 schrieb postgis <at> jochem.name: >> > Hi, >> > >> > what I want to do is finding certain features in some distance around a >> > certain point. Those features should be located in some corridor between X >> > and Y km around this point. Currently I've solved this problem by >> > computing two bounding boxes of X and Y km around the point and taking the >> > difference of those. So far so good. >> > >> > But I don't want to have some quadratic box but a real circle - is there >> > any way to achieve this? >> > >> > Best regards, >> > Rainer >> > _______________________________________________ >> > postgis-users mailing list >> > postgis-users <at> postgis.refractions.net >> > http://postgis.refractions.net/mailman/listinfo/postgis-users >> _______________________________________________ >> postgis-users mailing list >> postgis-users <at> postgis.refractions.net >> http://pos _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
