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.
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Writing Your Name Big Enough to be Seen from Space

Every now and then I delve into tag surfer and find something new and interesting.  This time, it led me to a post on writing your name large enough to be seen from space: http://andrewlainton.wordpress.com/2011/07/23/writing-your-name-in-the-sand-big-enough-to-be-seen-from-space/ Sometimes though, what you write is not about you personally, but a larger obsession.  In the same venue, but less personal: I should note, I’m not a Cavs fan, being … Continue reading Writing Your Name Big Enough to be Seen from Space

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Database, Database Optimization, LiDAR Shootout, PostGIS, SQL

LiDAR Shootout! — New Chart, Final Results

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

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Database, Database Optimization, LiDAR Shootout, PostGIS, SQL

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!

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Other

HTML Tags for code pre & code tags

I’ve spent little time looking at the formatting on my blog.  As the code has gotten longer, it’s gotten unacceptable that tabs and other formatting don’t show up correctly.  A little google-fu and thanks to this blog post: http://www.sohtanaka.com/web-design/styling-pre-tags-with-css-code-block/ I’ve reformated 25+ of my posts with more readable code with tabs and the whole bit.  I could go through and reformat everything, but I probably … Continue reading HTML Tags for code pre & code tags

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Database, Database Optimization, GeoServer, PostGIS

Contours– Symbolized from a single table

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

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Ecology, Image Processing, ImageMagick, Landscape Position

Landscape Position Continued– Median and ImageMagick

Highlighting ridges with 250ft buffer (on 2.5ft DEM) with just ImageMagick: convert lscape_posit.png -median 100 median100.png composite -compose difference lscape_posit.png median100.png difference_median100.png Input: Output: BTW, median calculations of this size are slow, even in ImageMagick. Continue reading Landscape Position Continued– Median and ImageMagick

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Ecology, Image Processing, ImageMagick, Landscape Position, POV-Ray

Landscape Position Continued– absolutely relative position calculation

I apologize in advance– this first post will be heavy on code, short on explanation. Landscape position, e.g. previous posts, can be trivial to calculate, but to make the calculations scalable to a large area, some batching is necessary. In this case, instead of a McNab index, we’re calculating the traditional GIS landscape position. Enter my favorite non-geographic tool, PovRay… . To the difference between, … Continue reading Landscape Position Continued– absolutely relative position calculation

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GeoServer, GeoWebCache

WMS vs. WMTS and GetFeatureInfo Requests

How to get GetFeatureInfo requests to perform against GeoWebCache?  Just don’t.  I’m unclear as to whether it is problematic to do this because of a known bug or known implementation differences between the (unofficial) WMTS standard as implemented by OpenLayers and GeoServer, but in Googling for answers to how to perform a GetFeatureInfo request against GeoWebCache, I discovered a workaround (logged here for example).  The … Continue reading WMS vs. WMTS and GetFeatureInfo Requests

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