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Raster Data: Elevation & Land Cover

Raster Data: Elevation & Land Cover. Biodiversity Informatics Training Workshop June 2013. Outline. Digital Elevation Models Derived surfaces SRTM Imagery & Land Cover GLCC QGIS Demo Import, project, extract. Raster - Digital Elevation Model. DEMs

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Raster Data: Elevation & Land Cover

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  1. Raster Data: Elevation & Land Cover Biodiversity Informatics Training Workshop June 2013

  2. Outline • Digital Elevation Models • Derived surfaces • SRTM • Imagery & Land Cover • GLCC • QGIS Demo • Import, project, extract

  3. Raster - Digital Elevation Model • DEMs • digital representations of terrain elevation based upon measures from regular intervals • Vary in area covered • 30 x 30 meters

  4. National Elevation Dataset 3, 10, 30 resolution Seamless

  5. Raster - Digital Elevation Model • SRTM (Shuttle Radar Topography Mission) • Space shuttle Endeavour on February 11 - 22, 2000 • 16 times a day (176) • 80% of earth • Radar signal to elevation • 1 arc-second (~30-meter) U.S. only • 3 arc-second (~90-meter) Global

  6. Raster - Digital Elevation Model • SRTM (Shuttle Radar Topography Mission) • Radar interferometry • Two radar images from 2 different locations • Difference between images • 60 meters apart

  7. Raster - Digital Elevation Model • Format • .bil • .tif (GeoTIFF) • Projection information • Geographic • WGS84

  8. Surface Analysis • Slope • steepness of a unit of terrain • Aspect • direction a unit of terrain faces

  9. Slope • Measurements • Degree • Percent

  10. Surface Analysis • Slope • steepness of a unit of terrain • Aspect • direction a unit of terrain faces

  11. Aspect • Aspect • Direction a unit of terrain faces • degrees from north

  12. Aspect • Further processing • NorthEastNess – SouthWestNess • sin(( [Aspect] + 45 ) * 3.14159/180)) • Careful of flat area (-1) • Circle data sometimes requires special processing

  13. Raster – Satellite Imagery 10 x 10

  14. Imagery • Aerial photography • Satellite

  15. Imagery • Aerial photography • Photo taken from above • Typically an aircraft • Satellite imagery • Orbital

  16. Great Plains 1962 Moffett Airfield

  17. Imagery • Aerial photography • Satellite

  18. Imagery • Satellite • Collects data from different wavelength • Bands • Landsat 7 collects from 0.5 – 1.1

  19. First images: 1946 65 miles (105 km) above earth

  20. Landsat ETM – Tahiti July 11 2001

  21. Imagery • Satellites (instrument) • MODIS • AVHRR • SPOT • LandSat • Considerations • Temporal • Resolution • Spectrum measured (bands)

  22. Imagery • Land Cover • Earth surface characteristics • Land Use • Land utilization • Derived from satellite data classification • Supervised • Unsupervised • Categorical data

  23. Imagery • Supervised • Provide reference (field or image sample) • Classify all pixels • Unsupervised • Compute clusters • Identify groups

  24. Imagery • Global Land Cover Characterization (GLCC) • Unsupervised classification of AVHRR

  25. Imagery • Global Land Cover Characterization (GLCC) • Temporal • 1992-1993 • Resolution • 1 km • Format • .bil • .tif (GeoTIFF) • Projection • Lambert

  26. Imagery • Considerations for data extraction • Format • GDAL (Geospatial Data Abstraction Library) • 1.9.0 supports 120 raster formats • Match projections

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