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Geographic Entities Classification in GIS and Reclassification Methods

Learn about classifying geographic entities in GIS using methods like Anderson Land Cover classification. Explore raster and vector reclassification, buffer operations, moving window filters, terrain classification techniques, and more.

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Geographic Entities Classification in GIS and Reclassification Methods

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  1. Classification • Classification • to put ‘things’ (geographic entities in GIS) into categories • Reclassification • to put ‘things’ in different, often more general, categories • results in a new data layer

  2. Classification • An example classification: Anderson Land Cover classification (Anderson et al., 1976) 1 urban or built-up 2 agricultural 3 rangeland 4 forest ... 9 41 deciduous forest 42 evergreen forest 43 mixed forest

  3. 2 1 2 1 1 1 3 2 2 3 1 2 1 2 1 1 3 2 2 3 2 1 2 1 1 1 3 2 3 2 1 1 1 1 1 1 2 4 2 4 1 1 1 1 1 1 2 4 2 4 Classification • Raster reclassification: land cover 1 grain crops 2 orchards 3 residential 4 commercial 1 agricultural 2 non-agricultural

  4. 32 1 39 1 2 45 47 2 2 43 1 31 1 38 42 2 43 2 2 44 37 1 39 1 45 2 45 2 46 2 42 2 43 2 51 3 3 52 3 51 47 2 47 2 55 3 3 54 3 56 Classification • Raster reclassification: temperature (interval) Grid cell value = temperature (F) 1 31 - 40 2 41 - 50 3 51 - 60

  5. Classification • Vector reclassification: land cover • line dissolve (map dissolve) 2 3 1 2 1 4 1 grain crops 2 orchards 3 residential 4 commercial 1 agricultural 2 non-agricultural

  6. Classification • Buffer: classification of within/without a given proximity • vector: a polygon ‘around’ a feature Line buffer Point buffer Polygon buffer

  7. Classification • Buffer • doughnut buffer (e.g. within 10 meters but not within 5 meters Buffer polygon 5 10 Hole

  8. Classification • Buffer • variable buffer: buffer distance varies by some feature attribute or friction surface

  9. Original line ID Dist A 3 B 2 C 5 B A C 4 6 10 Buffer polygon

  10. 2 0 2 0 0 2 0 2 0 2 0 2 1 1 1 1 1 1 2 0 0 2 1 1 0 1 1 1 2 0 0 2 1 1 1 1 1 1 0 2 2 0 0 2 2 0 0 2 2 0 Classification • Raster buffer • raster surface of within/not within proximity Reclassify: 1 within 1 unit 0 not within 1 unit Spread operation from buffered feature (0)

  11. Classification • Moving window • also called roving window, neighborhood function, filter • derived from image processing • raster data model only • assigns the value of a neighborhood of grid cells to one particular grid cell (kernel) • high pass filter - exaggerates local differences • low pass filter - smooths local differences

  12. 32 32 39 39 45 45 47 47 43 43 31 31 32 38 42 42 43 43 44 44 37 37 39 39 45 45 45 45 46 46 42 42 43 43 51 51 52 52 51 51 47 47 47 47 55 55 54 54 56 56 Classification Move window one cell over and begin again (use original data values) • Moving window • high pass filter kernel 3 x 3 window: multiply kernel (center grid cell) by 9 and subtract the other cell values - assign resulting value to the kernel

  13. 32 32 39 39 45 45 47 47 43 43 31 31 38 39 42 42 43 43 44 44 37 37 39 39 45 45 45 45 46 46 42 42 43 43 51 51 52 52 51 51 47 47 47 47 55 55 54 54 56 56 Classification Move window one cell over and begin again (use original data values) • Moving window • low pass filter kernel 3 x 3 window: average all values in window - assign resulting value to the kernel

  14. Classification • Moving window - defining the window • windows can be any number of cells in width and length • windows can be defined by a radius (e.g. including grid cells whose centroid is within the radius) • windows can assign maximum, minimum, etc. to the kernel

  15. Classification • Neighborhood operations for vector • how many other cities within a certain distance of each city • which city has the maximum population of all cities within a certain proximity from each city City Distance buffer

  16. Classification • Terrain classification • slope • aspect (orientation) • intervisibility

  17. 32 32 34 39 43 33 33 36 43 44 34 35 44 45 46 42 43 47 52 55 47 47 52 54 56 Classification • Terrain classification • Digital Elevation Model (DEM) • a raster grid of elevation values

  18. 32 32 32 32 34 34 39 39 43 43 33 33 35 35 34 34 43 43 44 44 34 34 35 35 44 44 45 45 46 46 42 42 43 43 53 53 52 52 55 55 47 47 47 47 52 52 54 54 56 56 Classification • Terrain classification: Slope (rise/run) DEM Percent Slope 19 Elevation in meters resolution = 100 meters 53 - 44 = 19 meters 19 / 100 = .19 or 19 % slope

  19. 32 32 32 32 34 34 39 39 43 43 33 33 35 35 34 34 43 43 44 44 34 34 35 35 44 44 45 45 46 46 42 42 43 43 53 53 52 52 55 55 47 47 47 47 52 52 54 54 56 56 Classification • Terrain classification: Aspect (orientation) DEM Aspect 0 Elevation in meters resolution = 100 meters Min = 34, North (0 deg) Max = 53, South (180 deg) Aspect = 0 deg

  20. Classification • Terrain Classification: Intervisibility

  21. 32 32 32 32 34 34 43 43 39 39 33 33 35 35 34 34 43 43 44 44 34 34 35 35 44 44 45 45 46 46 42 42 43 43 53 53 52 52 55 55 47 47 47 47 52 52 54 54 56 56 Classification observer • Terrain classification: Intervisibility DEM Visibility 0 1 Elevation in meters resolution = 100 meters Is there a higher elevation between observer and each cell? 0 not visible 1 visible

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