LiDAR Shootout!

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!

PostGIS and LiDAR, the saga completes?

I have to thank this post for the code that follows http://postgis.refractions.net/pipermail/postgis-users/2009-June/023660.html: I’ve been putting at this nearest neighbor for points problem for a few months now, never dedicating enough time to think in through, nor expending enough energy to be really great at SQL, let alone how it can be applied in spatial operations with an OGC compliant database like PostGIS.  But here’s my … Continue reading PostGIS and LiDAR, the saga completes?

PostGIS and LiDAR– oops!

I won’t offer much prelude.  Read this post, and this post first… . Inadvertently I demonstrated the value of spatial indices, i.e. I meant to use them and didn’t.  In attempting to sort my tables by their spatial index I got the following errors: ALTER TABLE lidar_ground CLUSTER ON lidar_ground_the_geom_idx; ERROR:  “lidar_ground_the_geom_idx” is not an index for table “lidar_ground” ALTER TABLE lidar_veg CLUSTER ON lidar_veg_the_geom_idx; … Continue reading PostGIS and LiDAR– oops!

Rethinking PostGIS Analyses– Remembering to CLUSTER

Something’s been nagging at me as far as the level of optimization (or lack there-of) that I did to my database before my other posts of using PostGIS to analyze LiDAR data (e.g. this post).  It seemed my results were remarkably slow, but I couldn’t put my finger on why that was problematic. Then, as I was testing a smaller lidar dataset in order to … Continue reading Rethinking PostGIS Analyses– Remembering to CLUSTER