Well, I made some mistakes in the last post, not the least of which is I used the wrong flag for creating an attribute field with elevation. What follows is a little more sophisticated. It takes us from a series of DEM tiles from which I want 2-foot and 5-foot contours (using gdal_contour), and then dumps those shapefiles into PostgreSQL using shp2pgsql. First we prep … Continue reading GDAL Contours (cont.)
Just another quick vignette. From the Ohio Statewide Imagery Program (OSIP) there is a 1-meter DEM for all of Ohio. To get contours from this dataset, one approach is to use GDAL tools, i.e. gdal_contours. As I’m working on a Mac today, I used Kyng Chaos pre-compiled Frameworks: http://www.kyngchaos.com/software:frameworks Then I needed to update my path variable in the BASH shell: export PATH=/Library/Frameworks/GDAL.framework/Programs:$PATH Now we … Continue reading GDAL Contours
At home, I work on a Mac, so when I want to do work here, my scripting language changes. In this case, I prefer BASH as my control script. I downloaded libLAS and did the standard Unix ./configure, make, sudo make install dance in the decompressed libLAS directory ./configure make sudo make install Now I have some tools to manipulate LiDAR las files at home. … Continue reading LiDAR data in BASH using libLAS
Ok, so the INSERT statements were too numerous for inputing the LiDAR point dataset (about a billion points… .) They kept crashing the postgres daemon. So, I used copy from a CSV file: COPY base.cuy_lidar_all FROM ‘c:/path/cuy_lidar_ground_veg.insert’ WITH CSV Keep your fingers crossed… . Continue reading COPY command psql– loading large LiDAR Point Dataset
A unique constraint implemented as a trigger checking hashed geometry seems like a good idea, that is until I applied it to a multi-10GB dataset. Not surprisingly, it starts off fast on inserts, and slows down a lot as time goes on. So, I thought I’d approach duplicates another way, by deleting them once they exist. So for my table: base.cuy_contours_2 I have hashed my … Continue reading Limitations to Trigger Based Unique Constraint
Below is my metacode for iterating through a grid of images to render the vegetation surface model from povray. The real code will be implemented in BASH and AWK, although this would be a perfect use of Python, if I knew how to use it… . PostGIS Tables: cuy_veg_points: Load veg points into database and make 2D geometry cuy_terrain_points: Load terrain points into … Continue reading Rendering a vegetation surface model using PovRay (cont.)
Early on, I was working on the problem of rendering a virtual forest based on real LiDAR data in order to do things like a detailed, vegetation included, viewshed. There are other things we can do with this data, including discovering the boundary of the canopy (and thus find canopy gaps) and rendering a vegetation surface model. Let’s start with a single tree. If we … Continue reading Rendering a vegetation surface model using PovRay
For a variety of reasons, I want to load my whole LiDAR vegetation dataset into PostGIS. I have it in raw, unclassified LAS files, and broken into classified, space delimited text files as well. The unclassified LAS is nice, if I ever want to hone the data, but for now, we’ll assume the classified data are correctly classified by someone smarter than I am (a … Continue reading Loading LiDAR data in PostGIS
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