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

2. Rasters

3. 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 Elevation Dataset (NED)National Land Cover Dataset (NLCD

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.phphttp://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.phphttp://landcover- modeling.cr.usgs.gov/index.php

21. Questions? 21 5 min break

22. Part II 22 Demos & details