For a couple of months now I’ve been corresponding with Etienne Racine and Pierre Racine out of Montreal Laval University in Quebec City. They decided to take on the problem of finding the speed and accuracy of a number of different techniques for extracting canopy height from LiDAR data. They have been kind enough to allow me to post the results here. This will be … Continue reading LiDAR Shootout!
In a previous post, I restructured the contour data for display in GeoServer, e.g.: UPDATE base.contours_2 SET div_10 = CAST( contours_2.elevation % 10 AS BOOLEAN ), div_20 = CAST( contours_2.elevation % 20 AS BOOLEAN ), div_50 = CAST( contours_2.elevation % 50 AS BOOLEAN ), div_100 = CAST( contours_2.elevation % 100 AS BOOLEAN ), div_250 = CAST( contours_2.elevation % 250 AS BOOLEAN ); The SLD styling … Continue reading Contours– Symbolized from a single table
In an earlier post, I was frustrated with the intersection of a polygon and line datasets coming out as a geometry collection instead of a simple line dataset as expected. Nicklas Avén was kind enough to point out that this is a natural consequence of the logic of an intersection, the definition of ST_Intersects is: Returns TRUE if the Geometries/Geography “spatially intersect” – (share any … Continue reading The PostGIS learning Curve: ST_Within and ST_Crosses
So, loading was easy, and all worked well. Viewing was fine. What is my gripe? B-tree Indexing. What if I wanted to ensure I had only unique geometric records in my database? Continue reading PostGIS Gripe—Limits to Postgre’s B-tree indexing
Smathermather's Weblog 