Thank-you for the help. I defined the problem a little better and took your advice and asked in postgis users: http://www.postgis.org/pipermail/postgis-users/2012-January/032056.html
Dave On Wed, Jan 11, 2012 at 11:20 PM, Andy Colson <a...@squeakycode.net> wrote: > On 01/11/2012 07:14 PM, David Waddy wrote: > >> If I have a table of the following form: >> >> id (integer) event_time (timestamp) lat_lon (polygon) >> 3497 1977-01-01 00:00:00 >> ((-64.997,45.975),(,(-64.9981,**45.975),(-64.8981,45.875),(-** >> 64.9978,45.9751)) >> 3431 2007-06-06 01:00:00 >> ((-64.971,45.982),(-64.921,45.**982),(-64.972,45.982),(-64.** >> 973,45.98209),(-64.97,45.**98237)) >> 3498 1977-01-01 00:00:00 >> ((-64.97838,45.9778),(-64.**9783,45.97767),(-64.978,45.** >> 977),(-64.9781,45.97728),(-64.**9781,45.97714),(-64.977,45.**976)) >> ... >> >> How would I return a list of the latest events for a particular >> lat/lon region? More precisely, how would a return a result set with >> the greatest event times with polygons that don't intersect any other >> polygon in the result set? >> >> Any help would be greatly appreciated, >> Dave >> >> > Are you using PostGIS? Assuming yes, try something like: > > select * from theTable a cross join theTable b on not (a.lat_lon && > b.lat_lon) order by event_time > > Also try the postgis news group, there are people there with more > experience with the postGIS functions. > > Your two questions dont seem to be asking the same thing, though. One > asks for a particular region. The second for a region that doesn't > intersect with any other's. I went for the second, cross joining the table > to itself, so every record with be compared to every other record, which is > gonna be a huge number of comparisons. So it'll be slow. > > -Andy > -- David Waddy Waddy & Colpitts Ltd. 99 Milky Way Colpitts Settlement, NB E4J 0B6 Canada tel: 506-372-4564 http://www.littleriver.ca
