Fulcrum by Spatial Networks is an interesting and very useful hosted service for collecting geo data in the field with whatever smartphone or tablet you already own. It works well, so long as you just want to collect points, and the field building capabilities are quite extraordinary. Also, for many applications, it’s cheaper than custom solutions, so it hits that sweet spot well. If you’ve … Continue reading Normalizing tables in PostgreSQL: experiments with Fulcrum
In a previous couple of posts (this one, and this one), we dealt with point rotations, first with bounding box searches, and then with nominal use of operators. First we create a function to do our angle calculations, then use select to loop through all the records and do the calculations. Within our function, first we find our first (in this case) five nearest streets … Continue reading Cartography and USGS — Fake Building Footprints in PostGIS now with distance operator (part 2)
Normally, my blog is a bit of a monologue. It’s not a bad thing, but can be a little lonely. Every now and then I get a great (and often doubtful) comments, which enhances things considerably. What follows is some dialog about the LiDAR shootout series, largely between Etienne and Pierre, posted with their permission: Pierre: “Etienne, Stephen, “I really appreciate the benchmark work you … Continue reading Dialog– What qualifies as a benchmark? Part 1
In reviewing the final numbers and charts from Etienne and Pierre, above are the results we see. The only revision is a moderate increase in speed for the PG Raster query. Final results in speed for lastools– ~350,000 points per second. In other words– off-the-charts fast. And the initial RMSE of ~25 feet was a mistake– it is probably closer to 0.2 feet. Stay tuned … Continue reading LiDAR Shootout! — New Chart, Final Results
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
Naively structured data is my bane– the desire (and need) to get stuff done so often overtakes the time needed to do things the better way. So, we bootstrap. A long time ago, we managed to load in a few tens of gigs of contour data into PostGIS, partitioned it into 2ft, 10ft, 20ft, 50ft, 100ft and 250ft tables using select queries with a modulus … Continue reading Contours– Structuring PostGIS data for viewing with GeoServer
There’s much to be said for knowing your data in order to best optimize the analysis of it. Beyond all other bits of cleverness, having a functional understanding of your problem is the first step toward conceiving an intelligent and efficient solution. One thing that I didn’t do two posts ago was to spend any time deciding how far out the search for nearby points … Continue reading Further optimization of the PostGIS LiDAR Vegetation Height Query
I have completed 4 out of 6 of my triggers for maintaining boundary data in PostGIS. This is a follow-up to this post. If you haven’t read my PostGIS trigger post, follow this link and come back. I’ll wait. Go on. Back? OK. So I’ve implemented my property boundary triggers. I need about 6-7 different versions of our boundary for cartographic reasons– some which are … Continue reading Trigger Speeeeed, or triggers and data maintenance in PostGIS
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?