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Fundamentals of Raster Data Model in GIS

Explore raster representation in GIS, raster resolution, encoding methods, ArcGIS usage, and compression techniques. Learn about chains and block codes, as well as quadtree partitioning in this informative lecture presentation.

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Fundamentals of Raster Data Model in GIS

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  1. GUS: 0262Fundamentals of GIS Lecture Presentation 6: Raster Data Model Jeremy Mennis Department of Geography and Urban Studies Temple University

  2. Raster Data Model • A raster representation is composed a series of layers, each with a theme • Typically used to represent ‘field-like’ geographic phenomena

  3. Regular Tessellations Squares Triangles Hexagons

  4. Irregular Tessellations

  5. Raster Grid • but most common raster is composed of squares, called grid cells • grid cells are analogous to pixels in remote sensing images and computer graphics

  6. 1 1 1 2 3 1 1 1 2 3 2 2 2 2 2 4 4 4 2 3 4 4 4 2 3 Raster Resolution The distance that one side of a grid cell represents on the ground = grid cell resolution The higher the resolution (smaller the grid cell), the higher the precision, but the greater the cost in data storage

  7. Raster Data: Encoding

  8. Raster Data: Encoding

  9. 1 1 1 2 3 1 1 1 2 3 2 2 2 2 2 4 4 4 2 3 4 4 4 2 3 Raster and RDBMS Raster layer can be attached to a RDBMS ID Land Use • 1 Agricultural • 2 Road • Residential • Industrial

  10. Raster Data: ArcGIS

  11. Raster Data: ArcGIS

  12. Raster in ArcGIS – Floating Point

  13. Raster in ArcGIS - Integer

  14. Converting Polygons from Vector to Raster

  15. Data Compression Common Methods: • run length encoding • value point encoding • chain codes • block codes • quadtrees

  16. Run Length Encodingand Value Point Encoding

  17. 1 1 1 2 3 1 4 4 4 3 2 4 4 4 2 4 4 4 4 3 4 4 4 4 3 Raster Chain Codes directions around the boundary of a region Value 4 North 1 East 1 North 2 East 2 South 3 West 3 Start

  18. 1 1 1 2 3 1 4 4 4 3 2 4 4 4 2 4 4 4 4 3 4 4 4 4 3 Raster Bock Codes two dimensional run length encoding 1 1 1 1 2 3 1 2 1 4 4 4 3 2 3 2 4 4 4 2 3 4 4 4 4 4 3 4 5 4 4 4 4 3 5 1 2 3 4 5 1 2 3 4 5

  19. Quadtree a partitioning of heterogeneous space into quarter sections

  20. Quadtrees • node is a quadrant that is heterogeneous • leaf is a quadrant that is homogeneous • quadrants are assigned an ID number according to their position and level

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