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Vector File Formats
• E00: Coverage exchange format– Decompress to get a coverage file
• KML: Keyhole Markup Language– Not georeferenced– Maybe with a prj file?
• STDS: US Government’s new vector format
Geo-Referenced Raster
• Known Projection and Datum
(X1,Y1)
(X2,Y2)
(X4,Y4)
(X3,Y3)
Geo-Referenced Raster
• Known Projection and Datum
• Width and height of a pixel in map units
(X1,Y1)
Width in Pixels
Height in pixels
Geo-Referenced Raster
• Known Projection and Datum
(X1,Y1)
(X3,Y3)
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
“No-Data” or NULL Values
• Rasters are always rectangular
• No-Data values are “transparent” and are not used for calcualations
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”
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
Not Geo-Referenced
• BMP
• PNG
• GIF
• Maybe with a world file and prj?
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!)
JPEG
• Joint Photographic Experts Group
• Widest used photo format
• JPEG2000– Completely new format!– Can be georeferenced
GRIDS
• ESRI’s native raster format
• Pyramids
• Not an exchange format!
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
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!
Digital Raster Graphic
Digital Elevation Model (DEM)
Hill-shade
Calculating SlopeDEM Cross Section
Aspect – Direction of the slope
Slope
Aspect (Direction)
Angle
Rise
Run
Slope = (Rise/Run) * 100%
Hill-shade
This weeks lab
• Download DEM
• Create slope, aspect, hill-shade maps
• Make a map showing all 4 types
• How many scale bars do you need?
• How many legends to you need?