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Rasters

GIS in the Sciences ERTH 4750 (38031). Rasters. Steve Signell , Instructor (signes@rpi.edu) Robert Poirier, TA (poirir@rpi.edu) School of Science Rensselaer Polytechnic Institute Monday, February 2, 2014. Rasters. Rasters. Rasters are tesselations

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Rasters

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  1. GIS in the Sciences ERTH 4750 (38031) Rasters Steve Signell, Instructor (signes@rpi.edu) Robert Poirier, TA (poirir@rpi.edu) School of Science Rensselaer Polytechnic Institute Monday, February 2, 2014

  2. Rasters

  3. Rasters • Rasters are tesselations • A tessellation is a partition of space into mutually exclusive cells that together make up the complete study area • There are two groups of tessellations: • Regular tessellations, the cells are the same shape and size • Irregular tessellations, the cells vary in shape and size

  4. Regular tessellations • All regular tessellations have in common that the cells are of the same shape and size, and the field attribute value assigned to a cell is associated with the entire area occupied by the cell Reality Regular tessellation

  5. Irregular tesselations • Triangulated Irregular Networks (TIN) • Each plane fitted through three anchor points has a fixed gradient (Slope)

  6. Raster types Two major types of raster data: • Continuous • Discrete, or ‘thematic’ National Land Cover Dataset (NLCD National Elevation Dataset (NED)

  7. Resolution & Scale • The size of the area that a single raster cell represents is called the raster’s resolution • Independent of scale

  8. Resolution & Scale

  9. Zones & Regions • Zone: Any two or more cells with the same value belong to the same zone • Region: Each group of connected cells in a zone is considered a region

  10. Continuous Rasters • Digital Elevation Model (DEM) • National Elevation Dataset (NED)

  11. National Elevation Dataset • primary elevation data product of the USGS • Seamless for US and territories • Compiled from contour maps, remote sensing: SRTM, LiDAR, and more

  12. National Elevation Dataset • USGS contour maps • Resolution: 10-30m • Not emperical • Quality varies by surveyor/map

  13. National Elevation Dataset • Shuttle Radar Terrain Model (SRTM) • Resolution: 30m • Holes

  14. National Elevation Dataset • LiDAR (Lilight, DARradar) • High Resolution (sub cm) • Multiple returns

  15. National Elevation Dataset • Updated regularly to reflect better data, changes in the landscape

  16. National Elevation Dataset Terrain Modeling

  17. National Land Cover Dataset Land Classification

  18. National Land Cover Dataset • NLCD derived from Landsat, a series of multi-spectral remote sensing satellites.

  19. National Land Cover Dataset • Landsat 8 & 7 • Multispectral ( Infrared- UV) • New data every 8 days • http://landsat.usgs.gov/gallery.php

  20. National Land Cover Dataset • Every ~ 5-10 years • http://www.mrlc.gov/ • http://landcover-modeling.cr.usgs.gov/index.php

  21. Questions? 5 min break

  22. Part II Demos & details

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