Embed Size (px)
DESCRIPTION
GIS in the Sciences ERTH 4750 (38031). Rasters. Steve Signell , Instructor ([email protected]) Robert Poirier, TA ([email protected]) School of Science Rensselaer Polytechnic Institute Monday, February 2, 2014. Rasters. Rasters. Rasters are tesselations - PowerPoint PPT Presentation
Citation preview
Rasters
Steve Signell, Instructor ([email protected])Robert Poirier, TA ([email protected])
School of ScienceRensselaer Polytechnic Institute
Monday, February 2, 2014
GIS in the SciencesERTH 4750 (38031)
Rasters
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
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
Regulartessellation
Irregular tesselations
• Triangulated Irregular Networks (TIN)
• Each plane fitted through three anchor points has a fixed gradient (Slope)
Raster types
Two major types of raster data:• Continuous• Discrete, or ‘thematic’
National Elevation Dataset (NED) National Land Cover Dataset (NLCD
Resolution & Scale
• The size of the area that a single raster cell represents is called the raster’s resolution
• Independent of scale
Resolution & Scale
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
Continuous Rasters
• Digital Elevation Model (DEM)• National Elevation Dataset (NED)
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
National Elevation Dataset
• USGS contour maps• Resolution: 10-30m• Not emperical• Quality varies by surveyor/map
National Elevation Dataset
• Shuttle Radar Terrain Model (SRTM)• Resolution: 30m• Holes
National Elevation Dataset
• LiDAR (Lilight, DARradar)• High Resolution (sub cm)• Multiple returns
National Elevation Dataset
• Updated regularly to reflect better data, changes in the landscape
National Elevation Dataset
Terrain Modeling
National Land Cover Dataset
Land Classification
National Land Cover Dataset
• NLCD derived from Landsat, a series of multi-spectral remote sensing satellites.
National Land Cover Dataset
• Landsat 8 & 7• Multispectral
( Infrared- UV)• New data every 8
days• http
://landsat.usgs.gov/gallery.php
National Land Cover Dataset
• Every ~ 5-10 years• http://www.mrlc.gov/• http://
landcover-modeling.cr.usgs.gov/index.php
Questions?
21
5 min break
Part II
22
Demos & details
