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NR 422: Raster Analysis

NR 422: Raster Analysis. Jim Graham Spring 2010. Continuous vs. Categorized. Continuous: Like photographs Satellite and aerial photos Best for analysis Categorized or discrete Land Cover Eco-regions Limited analysis Careful on precision and accuracy. Categorical vs. Continuous.

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NR 422: Raster Analysis

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  1. NR 422: Raster Analysis Jim Graham Spring 2010

  2. Continuous vs. Categorized • Continuous: • Like photographs • Satellite and aerial photos • Best for analysis • Categorized or discrete • Land Cover • Eco-regions • Limited analysis • Careful on precision and accuracy

  3. Categorical vs. Continuous

  4. “No-Data” or NULL Values • Rasters are always rectangular • No-Data values are “transparent” and are not used for calculations

  5. Geo-Referenced Raster • Known Projection and Datum • Width and height of a pixel in map units (X1,Y1) Height in pixels Width in Pixels

  6. Geo-Referenced Raster • Known Projection and Datum (X1,Y1) (X3,Y3)

  7. Types of Rasters • Digital Elevation Model (DEM) • Digital Raster Graphic (Topos) • Satellite and Aerial Photos • Land Cover & other natural characteristics • Cost Distance & other economic • Population, taxes, etc. • Your own!

  8. Digital Raster Graphic

  9. Digital Elevation Model (DEM)

  10. Hill-shade

  11. Contours

  12. Contours 2200m 2100m 2000m 1900m DEM Cross Section

  13. Slope

  14. Calculating Slope DEM Cross Section

  15. Aspect – Direction of the slope Aspect (Direction) Slope Rise Angle Run Slope = (Rise/Run) * 100%

  16. Aspect

  17. Hill-shade

  18. Creating a Hillshade • Obtain a DEM • Crop to Desired Area • Create Hillshade • Apply color ? To DEM • Add DEM over Hillshade with Transparency

  19. Screen shots: • Hillshade dialog • Colorizing dems • Transparency

  20. Spatial Analyst Extension • Make sure “Spatial Analyst” is Checked

  21. Tool Bar • Right-click in the menu area • Select “Spatial Analyst”

  22. Hill-shading • Azimuth: “Direction” of the sun relative to the ground. 0 is north. • Altitude: Angle from the horizon to the sun. North Azimuth Altitude Horizon

  23. “Colorize” the DEM

  24. Make the Hillshade Transparent

  25. Continuous vs. Categorized • Continuous: • Like photographs • Satellite and aerial photos • Best for analysis • Categorized or discrete • Land Cover • Eco-regions • Limited analysis • Careful on precision and accuracy

  26. “GeoReferenced” File Formats • GRID: ESRI’s format • GeoTIFF: Excellent support • MrSID: LizardTech • IMG: ERDAS • ECW: ERMapper • BIL, BIP, BSQ: See header (w/prj) • “ASCII” or “GRID ASCII” (w/prj)

  27. World Files • Contains: • X-dimention Pixel size in map units • Y-axis rotation • X-axis rotation • Y- dimension Pixel size in map units (negative) • X-coordinate of upper-left pixel • Y-coordinate of upper-left pixel • Image file contains width and height

  28. Not Geo-Referenced • BMP • PNG • GIF • JPEG • Maybe with a world file and prj file?

  29. JPEG • Joint Photographic Experts Group • Widest used photo format • Not for use with vectors • JPEG2000 • Completely new format! • Can be georeferenced Edge of Rocky Mountain National Park Boundary with high JPEG compression

  30. Tagged Image File Format • TIFF • Can be georeferenced (GeoTIFF) • Can tell in ArcCatalog or ArcMap • TIFF w/world file • Also need Projection and Datum (prj?) • Can be compressed • Run-length – Categorical data • LZW – Categorical data • Huffman encoding – Categorical data • JPEG- Continuous data (don’t used on Categorical data!)

  31. GRIDS • ESRI’s native raster format • Pyramids • Not an exchange format!

  32. ASCII format • NCOLS 10 • NROWS 9 • XLLCORNER 1000 • YLLCORNER 1000 • CELLSIZE 1 • NODATA_VALUE -9 • -9 -9 1 1 0 1 0 1 -9 -9 • -9 -9 1 1 2 2 2 1 1 -9 • -9 1 1 1 2 2 2 2 3 3 • Etc. • See example

  33. Types of Rasters • Land Cover: forest, grass, water, roads, urban • Digital Elevation Model: DEM • Aerial Photos • Satellite Photos • Scanned: DRG, 24k Topos • Derived rasters: lots!

  34. Derived Rasters • Land Cover from satellite and aerial • Topography: Slope, aspect, hillshade • Ecoregions • Suitable Habitat • Flood plains • Geological Regions

  35. Raster To Vector • Satellite & Aerial • Land Cover: roads, forests, etc. • Buildings • DEMs • Contours • Peaks & Valleys • Stream Networks • Watersheds

  36. Vector To Raster • Drawing! • Points of interest • Roads • Water bodies • Contours

  37. GIS Analysis Raster to Vector Vector to Raster Analysis Results

  38. Raster Analysis • Topography: Slope, aspect, contours • Raster Math • Statistics: min, max, mean, std. dev. • Distance • Density • Interpolation • Classification • Raster / Vector Conversions

  39. Raster Math • A matrix of pixels Columns Rows

  40. Spatial Analyist

  41. Analysis Environment • Spatial Reference (Coordinate System) • Make them the same • Extent • Area of interest • All rasters should overlap • Cell Size • Largest of all rasters or larger

  42. Spatial Analyst: General

  43. Spatial Analyst: Extent

  44. Spatial Analyst: Cell Size

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