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Geo-Referenced Raster

Geo-Referenced Raster. Known Projection and Datum. (X1,Y1). (X4,Y4). (X2,Y2). (X3,Y3). Geo-Referenced Raster. Known Projection and Datum Width and height of a pixel in map units. (X1,Y1). Height in pixels. Width in Pixels. Geo-Referenced Raster. Known Projection and Datum. (X1,Y1).

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Geo-Referenced Raster

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  1. Geo-Referenced Raster • Known Projection and Datum (X1,Y1) (X4,Y4) (X2,Y2) (X3,Y3)

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

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

  4. 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

  5. Categorical vs. Continuous

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

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

  8. 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

  9. 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!)

  10. JPEG • Joint Photographic Experts Group • Widest used photo format • JPEG2000 • Completely new format! • Can be georeferenced

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

  12. IMG – ERDAS Imagine • Esri’s new default • Internal geo-referencing • Recommended over Grids

  13. ASCII format (asc) • 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.

  14. 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!

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

  16. Digital Raster Graphic

  17. Hill-shade

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