Hello All - Looking for a US layer that breaks the country into 3 distinct contours; urban, suburban and rural. Vector preferred, but recommendations for raster good as well. I have found several urban layers from various sources, but at am a loss as how to approximate suburban and rural areas without some generic buffer distance assumptions. Raster imagery of land use, given the need for a US layer, seem cumbersome to join tiles and then contour. But been wrong before. Any and all ideas welcome. Thanks in advance for the support past and present. -----Original Message----- From: Dyan Catamaran [mailto:[EMAIL PROTECTED]] Sent: Friday, January 19, 2001 1:28 PM To: [EMAIL PROTECTED] Subject: MI-L Progressive buffers Hi Users Here is my spatial challenge. Suppose I have a mapsheet with X polygons and I want to buffer one at the time using incremental distance and to perform an "intersect" SQL query on the buffer object. Let me explain: I have two layers: One with infestation polygons. Usually with small polygons. Other with base polygons. The base polygons cover the entire landscape and the infestation polygons are very small in size if compared with base ones. The idea is to associate indexes to the base polygons that depend of the distance of each polygon to the infestation and size of the infestation. EX: if a base polygon "A" is at distance "D" of an infestation "I" of size "S", the base polygon would get and index "X". I thought on to create a progressive or incremental distance buffer around the base polygon and at each buffer increment do a test to check if the buffer intersects any infestation. If doesn't intersect then do another buffer increment and proceed testing until the distance of 4 Km. If there is no intersection, the index is Zero. This procedure has to be performed on one polygon at the time and I have hundreds of polygons. After this incremental buffer plus test is done, the buffer should be discarded and the "pointer" moves to another base polygon. This way after exhausted the base map, all the landscape would be indexed based on the distance and intensity of the infestation. I see some trouble before hand. The buffer can be generated in the same layer or in the cosmetic layer. But the SQL intersects works on all the objects if I generate in the same layer. If I save the cosmetic layer to consider only one buffer on the selected base polygon I would have thousands of single buffer layers. Out the fact I have to open each one new single buffer layer, perform the SQL/Intersects and close it ...and do it again. It seems way too convolute for me. Can anyone shed some light here? I would appreciate any help or questions for further explanations. Dyan C. Catamaran GIS/RS Coordinator --------------------------------- Phero Tech Inc. www.pherotech.com [EMAIL PROTECTED] P:604-940-9944 F:604-940-9433 _______________________________________________________________________ List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, send e-mail to [EMAIL PROTECTED] and put "unsubscribe MapInfo-L" in the message body. _______________________________________________________________________ List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, send e-mail to [EMAIL PROTECTED] and put "unsubscribe MapInfo-L" in the message body.
