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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

Raster Data: Elevation & Land Cover

Biodiversity Informatics Training Workshop

June 2013

outline
Outline
  • Digital Elevation Models
    • Derived surfaces
    • SRTM
  • Imagery & Land Cover
    • GLCC
  • QGIS Demo
    • Import, project, extract
raster digital elevation model
Raster - Digital Elevation Model
  • DEMs
    • digital representations of terrain elevation based upon measures from regular intervals
  • Vary in area covered
    • 30 x 30 meters
slide4

National Elevation Dataset

3, 10, 30 resolution

Seamless

raster digital elevation model1
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
raster digital elevation model2
Raster - Digital Elevation Model
  • SRTM (Shuttle Radar Topography Mission)
  • Radar interferometry
    • Two radar images from 2 different locations
    • Difference between images
      • 60 meters apart
raster digital elevation model3
Raster - Digital Elevation Model
  • Format
    • .bil
    • .tif (GeoTIFF)
  • Projection information
    • Geographic
    • WGS84
surface analysis
Surface Analysis
  • Slope
    • steepness of a unit of terrain
  • Aspect
    • direction a unit of terrain faces
slope
Slope
  • Measurements
    • Degree
    • Percent
surface analysis1
Surface Analysis
  • Slope
    • steepness of a unit of terrain
  • Aspect
    • direction a unit of terrain faces
aspect
Aspect
  • Aspect
    • Direction a unit of terrain faces
    • degrees from north
aspect1
Aspect
  • Further processing
    • NorthEastNess – SouthWestNess
      • sin(( [Aspect] + 45 ) * 3.14159/180))
      • Careful of flat area (-1)
    • Circle data sometimes requires special processing
imagery
Imagery
  • Aerial photography
  • Satellite
imagery1
Imagery
  • Aerial photography
    • Photo taken from above
    • Typically an aircraft
  • Satellite imagery
    • Orbital
slide17

Great Plains 1962

Moffett Airfield

imagery2
Imagery
  • Aerial photography
  • Satellite
imagery3
Imagery
  • Satellite
    • Collects data from different wavelength
    • Bands
    • Landsat 7 collects from 0.5 – 1.1
slide21

First images: 1946

65 miles (105 km) above earth

imagery4
Imagery
  • Satellites (instrument)
    • MODIS
    • AVHRR
    • SPOT
    • LandSat
  • Considerations
    • Temporal
    • Resolution
    • Spectrum measured (bands)
imagery5
Imagery
  • Land Cover
    • Earth surface characteristics
  • Land Use
    • Land utilization
  • Derived from satellite data classification
    • Supervised
    • Unsupervised
  • Categorical data
imagery6
Imagery
  • Supervised
    • Provide reference (field or image sample)
    • Classify all pixels
  • Unsupervised
    • Compute clusters
    • Identify groups
imagery7
Imagery
  • Global Land Cover Characterization (GLCC)
  • Unsupervised classification of AVHRR
imagery8
Imagery
  • Global Land Cover Characterization (GLCC)
  • Temporal
    • 1992-1993
  • Resolution
    • 1 km
  • Format
    • .bil
    • .tif (GeoTIFF)
  • Projection
    • Lambert
imagery9
Imagery
  • Considerations for data extraction
  • Format
    • GDAL (Geospatial Data Abstraction Library)
    • 1.9.0 supports 120 raster formats
  • Match projections