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.
Analysis, Optics, Other, POV-Ray

Fast Calculation of Voronoi Polygons in PovRay

Yet further abuse to follow in the application of PovRay for spatial analyses– be forwarned… . Calculating Voronoi polygons is a useful tool for calculating the initial approximation of a medial axis. We densify the vertices on the polygon for which we want a medial axis, and then calculate Voronoi polygons on said vertices. I’ll confess– I’ve been using ArcGIS for this step. There. I … Continue reading Fast Calculation of Voronoi Polygons in PovRay

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Analysis, Database, PostGIS, PostgreSQL, SQL

What is the center line of a complex polygon? (cont. again!)

I didn’t remember that I had 4 previous post on this topic, but I’ve gotten a little obsessed with this problem– how to (with relatively little computational cost) kind the centerline of complex polygons, so we can extract flow lines from streams, label long complex polygons, easily generate the centerline parcel boundary line for river bound parcels, etc..  FYI, here are my 4 previous posts … Continue reading What is the center line of a complex polygon? (cont. again!)

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Analysis, Cartography, Database, PostGIS, PostgreSQL, SQL, Trail Curation, Trails

PostGIS Cartographic Effects– Cartoonify Nearly Coincident Lines

In my previous post, a long 24-hours ago, I proposed some automatic modification of line for cartographic reasons. I had some flaws in my code. The points were over-rotated by 45 degrees. Can you spot why? Tip: it’s a basic trigonometric mistake. Here’s the corrected code (though there may be a better way): An alternate approach is to only move those points that are too … Continue reading PostGIS Cartographic Effects– Cartoonify Nearly Coincident Lines

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Analysis, Cartography, Database, PostGIS, PostgreSQL, SQL, Trail Curation, Trails

PostGIS Cartographic Effects– Cartoonify Nearly Coincident Lines

I’m still working on this query, but I thought I’d post what I’ve done so far. My intent is to produce scale-dependent exaggeration of the distances between quasi-parallel lines. The reason for this is so that lines such as street lines which are nearly coincident at a particular viewing scale can be spread from each other, much in the same way great cartography lies a … Continue reading PostGIS Cartographic Effects– Cartoonify Nearly Coincident Lines

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Other

There’s an App for That, Alternate

codinggeekette, or Sarah Dutkiewicz and her husband introduced me to Linux and Open Source many years ago.  Running counter-culture is the genius that is @sadukie, so now she’s a Microsoft MVP.  We’ll forgive her that, since she does crazy stuff like setting up .net environments on Linux and other fun stuff.  Anyway, Sarah has a post on phone apps she likes and has proposed in … Continue reading There’s an App for That, Alternate

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Other

2011 in review — Laziest post possible

Happy New Year everyone!  In a beautifully global fashion, the first New Year wishes I received this year were out of Africa from two folks I follow on twitter.  In that same vein, my blog is comfortably global, with readers on all the continents, Antarctica notwithstanding.  As I used to do polar research, I suppose I should change that 6 out of 7 to 7 … Continue reading 2011 in review — Laziest post possible

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GDAL

gdal_warp, cutlines, and cwhere– simple tip for use on Linux

Mini GDAL tip of the day: gdalwarp, especially in combination with gdal_merge, is a powerful tool for doing all sorts on nice aggregation (read: mosaic’ing) of spatial raster data.  Unfortunately, at least with a google search, there’s very little to be found on demonstrating the use of queries in conjunction with cutlines, probably because in general these queries are not difficult to figure out. In … Continue reading gdal_warp, cutlines, and cwhere– simple tip for use on Linux

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Analysis, Ecology, GDAL

GDAL Slopes– Local Hydrologic Slope vs. the Standard Approach

Open Source software is not, of course just about warm and fuzzies, great support, rapid development cycles, shared costs, etc., it’s also about getting your hands dirty with someone else’s code and implementing stuff more quickly and more intelligently because of it, and hopefully learning something in the process.  You don’t have to poke under the hood to drive the car, but sometimes it’s nice … Continue reading GDAL Slopes– Local Hydrologic Slope vs. the Standard Approach

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Analysis, Ecology, Landscape Position, Other, POV-Ray

Landscape Position: Conclusion? (part 2)

From earlier post: “I’ve managed to pilot most of a fast high resolution landscape position workflow with PovRay as my magic tool. The final steps I hope to pipe through PostGIS Raster. In the meantime a screenshot and description: blues are riparian, raw ocre, etc upland categories, grey is mostly flat lake plain and mid slopes, all derived from just a high res DEM input … Continue reading Landscape Position: Conclusion? (part 2)

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