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Goals

Goals. Define a conceptually and computationally compatible definition of flat one based on the perception of flat can be applied globally Test the feasibility of open source software for conducting large-scale geographic analysis Produce a ‘flat map’ for the continental US

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Goals

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  1. Goals • Define a conceptually and computationally compatible definition of flat • one based on the perception of flat • can be applied globally • Test the feasibility of open source software for conducting large-scale geographic analysis • Produce a ‘flat map’ for the continental US • Eerr…I mean Kansas The Flat Map:A Perception Approach To Modeling Flat Terrain Joshua S. Campbell PhD Candidate - Geography University of Kansas GIS Day – 18 Nov 2009

  2. Conceptual Flat • Based on the human perception of flat • a terrain geometry interpreted by human vision • can occur in association with any type of landform (plains, river valleys, plateaus, glacial outwash...) • is not tied to any specific geomorphic process, (erosion/sedimentation, aeolian/fluvial/glacial)

  3. When does flat stop being flat? Calculate visibility at sea: Visibility (in miles) = (1.17 x sqrt (height)) x 1.15 Height = 6 ft Visibility = 3.3 miles or 5,310 meters A model of flat

  4. 30 meter rise 5,310 meter view Computation Flat • Multi-neighborhood DEM analysis (90m SRTM) • View to the horizon (3.3 miles) • 8 directions (N, NE, E, SE, S, SW, W, NW) • Minimum threshold of 0.32 degrees • Local Slope (3 x 3 window: 270m) 0 - 3% slope = flat

  5. 64-bit processing

  6. GRASS Processing in QGIS • r.in.gdal (55 times) • r.patch (mosaic) • g.region (change extents - tricky) • r.mapcalc (conditional statements: subset) • r.slope • r.horizon (8 directions) • r.recode (produce index layers) • r.mapcalc (sum: produce index) • r.statistics (zonal stats) • r.out.gdal (export to geotiff)

  7. Thank You! Presentation, KML files, and upcoming paper will be available at my blog: http://www.disruptivegeo.com ~2% of Kansas is flat

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