E.g. topography, temperature, rainfall, population000000010011011100221112112222200: shale1: sandstone0: rock well exposed1: 2: rock poorly exposed99.299.510099.399.8 100.6100.3 99.6 100.5ElevationRaster DEM (Digital Elevation Model)Digital Elevation Model: Any digital representation of continuous variation of relief over space.
•Value indicating classes–One value per cell but can has multiple attributes per value in value attribute table (VAT) 0000000100110111ValueCountRock typeRock name010SedimentaryShale16SedimentarySandstone
DEMA: YesB: No For discussion: Can elevation of the area be represented by vector data model?
What does a map look like?
•Real world features: discrete objects or continuous phenomena•Models: simplified version of real world features•Vector data model: points, lines, polygons•Raster data model: matrix of cells•Spatial data and attribute data•Shapefiles and geodatabase•A map represents a portion of the earth's surface•Map: Representation of real world by selected information•Spatial and attribute data are displayed together using map symbols and a legend.
•Scale model of Earth: globe
Globe distanceEarth distance =Graticule: Network of lines on globe or map representing latitude and longitude.Origin is at Equator/Prime Meridian intersection (0,0)Principal Scale
Longitudeline (Meridian)Range: 180°W –0°―180°ELatitudeline (Parallel)Range: 90°S –0°―90°NEquator, Prime Meridian0°Parallels converge as poles are approachedChristopherson (2001)Graticule: Network of lines on globe or map representing latitude and longitude.Origin is at Equator/Prime Meridian intersection (0,0)
- Geographic longitude- Geographic latitudeR - Mean earth radiusO –Geocenter: Earth mass center•A point on the surface of the Earth is referenced by its longitude and latitude values•Longitude and latitude are angles measured from the Earth's center to a point on the Earth's surface•Latitude values are measured relative to the equator and range from -90° at the South Pole to +90° at the North Pole•Longitude values are measured relative to the prime meridian at Greenwich and range from -180° when traveling West to 180° when traveling East from the prime meridian