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
Author: smathermather
My primary interest is in understanding ecological processes in a synoptic fashion. This has led me down a long study with Geographic Information Systems and Remote Sensing as they relate to ecology and biological processes.
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
Viewshed Analyses in Povray– Final Image
I completed this project a long time ago and have not blogged on it in over a year. None-the-less, I realized that I hadn’t posted any final images for the viewshed analysis with Povray. So here is the summer viewshed analysis. This is rendered with about (I think) 150,000 trees, each with 100,000+ leaves. The cell tower here is in red. The landscape colored in … Continue reading Viewshed Analyses in Povray– Final Image
IMCORR– using image correlation to georeference an image
IMCORR is a package distributed by the National Snow and Ice Data Center (did you know we have one of those?), or NSIDC, that performs image cross correlation between two images using a comparison between a moving image chip in each image. It measures the displacement (in pixels) between the objects found in the two images, and writes that out to a text file. It … Continue reading IMCORR– using image correlation to georeference an image
Digital Surface Model– a whole forest and more part Deux
Just another shot of our digital surface model of the forest. This time, I rendered it with all of the trees at base elevation 0 (zero), placed the orthographic camera at height 150, so our 16-bit range we’re rendering to should scale 0-150 feet to 0-65535 values, giving us a precision of 0.002 feet. The original LiDAR data has a precision of 0.01 feet, so … Continue reading Digital Surface Model– a whole forest and more part Deux
Digital Surface Model– a whole forest and then some
Let’s start putting some of the pieces together. Earlier, I presented a method for deriving a digital surface model from LiDAR data of a forest canopy, using a tree-shaped interpolator that scales the individual tree canopy shapes according to the height of the LiDAR return from the ground. Now I present the whole project, forest and all. I wanted to render my DSM at a … Continue reading Digital Surface Model– a whole forest and then some
Topographic Position Index and Ecological Land Type (warning completely unrefined not quite Geologic dribble– with bad maps :) …)
Warning. What follows is somewhat informed, but I’m no geologist. I just play one on wordpress. Understanding the basic underlying geology and associated topography plus site history helps us achieve a basic understanding of a sites ecological potential. At the most basic level, we expect different wildlife and vegetation dynamics in a floodplain vs. a mountain ridge. Classification of digital elevation models can be done … Continue reading Topographic Position Index and Ecological Land Type (warning completely unrefined not quite Geologic dribble– with bad maps 🙂 …)
Modeling (relative) Sub-Canopy Biophysical Variables with PovRay
One of my goals in modeling canopy height is to estimate sub-canopy biophysical variables that give indications of habitat suitability. For example, suppose we have a rare plant that is canopy gap dependent. How do we model it’s distribution? With a statewide LiDAR dataset from which we can derive canopy location and height, we can identify canopy gaps. While I haven’t gotten to the modeling … Continue reading Modeling (relative) Sub-Canopy Biophysical Variables with PovRay
Optimizing Pov-Ray include files– smaller trees with the same effect
One limitation I’ve run into in rendering large scenes of trees in PovRay, whether for fun for work is memory usage. I’ve found that about a half million trees is about as many as I can place on a 32-bit system before running out of memory. Sometime this year I’ll switch to 64-bits, but in the mean time, I hacked together a solution for reducing … Continue reading Optimizing Pov-Ray include files– smaller trees with the same effect
Batch processing resampling of DEMs
Yet again, working with that Ohio DEM dataset, I need some reduced resolution versions of the 2.5 foot DEMs. At a grand total of ~600 DEMs for a given county, it was time to batch, this time in Windows Command prompt. The neat thing is the variable substitution in the for-in-do command in the command prompt, where, e.g. for a file variable %f, the file … Continue reading Batch processing resampling of DEMs
Smathermather's Weblog 