Clipping Data w/ PostGIS continued
It finished, yay! A little Friday 5PM exuberance, I’m afraid. See previous post for explanation. Here is the clipped version: Continue reading Clipping Data w/ PostGIS continued
Category: PostGIS
Clipping Data
I loaded a set of contours into the database that are really nice, up-to-date LiDAR and breakline derived contours. The are engineering grade aerial contours, but they are a very big and complex dataset. So I’ve done what I had hoped was the hard part, using shp2pgsql, I’ve converted them to PostGIS insert statements and dumped them into the database only to find that some … Continue reading Clipping Data
LiDAR processing and analysis in PostGIS (I hope…).
Alright, so let’s begin again with some LiDAR processing in PostGIS. I really liked this discussion of multipoint conversions of LiDAR and other point datasets, but we won’t address making things more efficient here (yet). Besides, these aren’t just points– we do want to retain their attribution… . Now, any regular database user will recognize my nubeness reading this post. If you are that person, … Continue reading LiDAR processing and analysis in PostGIS (I hope…).
GDAL Contours (cont.)
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.)
COPY command psql– loading large LiDAR Point Dataset
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
Limitations to Trigger Based Unique Constraint
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
Rendering a vegetation surface model using PovRay (cont.)
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.)
Loading LiDAR data in PostGIS
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
Unique constraint on geometry continued
An actual example of using the hashed geometry to uniquely constrain geometry (nothing really new here, just an example of using what we learned in the last post with a new problem): I’ve got a contours dataset from the county where I work that is in 20 different shapefiles ranging in size from 500MB to 2GB. I want to put them into a PostGIS database … Continue reading Unique constraint on geometry continued
PostGIS Gripe—Limits to Postgre’s B-tree indexing—Followup
In an earlier post, I griped about the limits to Postgres B-tree indexing, in that for large PostGIS geometries, I couldn’t create a unique constraint for PostGIS geometry. Abe Gillespie (blame me not him for any mistakes in what follows), suggested that I hash the geometry and create an index on that. In a follow-up e-mail, he suggested a series of tests in a trigger … Continue reading PostGIS Gripe—Limits to Postgre’s B-tree indexing—Followup
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