The Problem We have to filter out the roads and ditches without removing streams that cross roads or follow them closely. I’m going to use PostGIS to find the intersection of the streams lines data with a buffered roads polygon. If the intersected line is less than 50% of the length of the stream line, […] via Filtering Roads from Extracted Streams Data — GeoKota Continue reading Using PostGIS for Hydrologic Modeling (reblog)
Ok, I’m not the first to come up with that name, but I like it so it’s staying for now. The problem space is this: Your web development team is good with forms. They build forms like diurnal animals wake — daily: day in, day out, day in, day out. They want to build a form for a mobile web app and it just happens to use … Continue reading Leaflet Crosshairs
Back in 2011 I wrote a post about GDAL, translating MrSID files and trimming off the artifacts so mosaics work. I’m revisiting some similar work this week and realized I had lost my copy of FWTools that can deal with MrSIDs. The Internet Archive came to the rescue. At some point LizardTech licensed a DLL that allowed for compilation compatible with FWTools licensing so we could … Continue reading GDAL tools of the trade: GDAL, MrSid, and nearblack revisited
More landscape position pictures — just showing riparianess. See also https://smathermather.wordpress.com/2014/11/22/landscape-position-using-gdal/ and https://smathermather.wordpress.com/2014/11/24/landscape-position-using-gdal-pt-2/ Map tiles by Stamen Design, under CC BY 3.0. Data by OpenStreetMap, under ODbL Continue reading Landscape Position using GDAL — PT 3
Just pretty pics today of estimated riparianess. If you prefer a bit of code, see previous post https://smathermather.wordpress.com/2014/11/22/landscape-position-using-gdal/ Continue reading Landscape Position using GDAL — PT 2
Hat tip again to Seth Fitzsimmons. I’ve been looking for a good, easy to use smoothing algorithm for rasters. Preferably something so easy, I don’t even need to write a little python, and so efficient I can run it on 30GB+ datasets and have it complete before I get distracted again by the next shiny project (a few hours). Seth’s solution? Downsample to a low … Continue reading Landscape Position using GDAL
The series and one additional example: Continue reading What is the center line of a complex polygon? Routing Stream and Rivers Part Two
Continuing my posts on the centerline of a complex polygon (you can work your way backward from here), here’s it’s application to a riverine system (legend: light blue river, black centerline derived from routing through the skeleton of voronoi polygons from a densified stream bank set + the skipped skeleton bits in pink– read through the series if you if you don’t grok that explaination): Continue reading What is the center line of a complex polygon? Routing Stream and Rivers
Anyone who has been following along at home knows I don’t think much like a DBA. Sometimes that’s good; mostly it’s probably bad. In this post, I hope it will be interesting. The problem of the day is how to take engineering contours derived from breaklines, a lidar point cloud, and all the lot, and do a good job interpolating that to a DEM. This … Continue reading Proper (ab)use of a database, contour interpolation using #postgresql #postgis #arcgis
I’ve had a series of posts (including this one) on finding the center line of a complex polygon– especially with an interest in finding the center line of streams and river bodies. We have to give credit to my colleague Tom Kraft for solving the polygon centerline problem. Tom struck upon the very elegant solution– derive the medial axis, and then use a few end … Continue reading What is the center line of a complex polygon? Routing as the solution
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