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Advanced GIS: Raster Conversion and Local Analysis

Learn about environment settings, vector to raster conversion, raster to vector conversion, raster to ASCII conversion, raster to raster conversion, raster to video conversion, and cell statistics in GIS.

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Advanced GIS: Raster Conversion and Local Analysis

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  1. ___________________________________________________________ Advanced GIS UNT Geography  • 3. Raster Conversion and Local Analysis • 3.1 Environment settings • 3.2 Vector to raster conversion • 3.3 Raster to vector conversion • 3.4 Raster to ASCII conversion • 3.5 Raster to raster conversion • 3.6 Raster to video conversion • 3.7 Cell statistics

  2. ___________________________________________________________ Advanced GIS UNT Geography  • 3.1 Environment settings - System wide settings that are used by every tool.

  3. ___________________________________________________________ Advanced GIS UNT Geography  • 3.1 Environment settings (cont.)

  4. ___________________________________________________________ Advanced GIS UNT Geography  • 3.1 Environment settings (cont.)

  5. ___________________________________________________________ Advanced GIS UNT Geography  • 3.1 Environment settings (cont.) Tool environment settings only apply to the current run of the tool and do not update the application environment settings.

  6. ___________________________________________________________ Advanced GIS UNT Geography  • 3.2 Vector to raster conversion Point Represented by a cell in raster. Line Represented by a series of connected cells in raster. Polygon Represented by a series of connected cells in raster.

  7. ___________________________________________________________ Advanced GIS UNT Geography  • 3.2 Vector to raster conversion (cont.) ❶ ❸ ❷

  8. ___________________________________________________________ Advanced GIS UNT Geography  • 3.2 Vector to raster conversion (cont.) Discussion: Can a polyline (Loop 288 in Denton, TX) or polygon (UNT campus) become a single cell after vector to raster conversion? Why or why not?

  9. ___________________________________________________________ Advanced GIS UNT Geography  • 3.3 Raster to vector conversion Raster to point

  10. ___________________________________________________________ Advanced GIS UNT Geography  • 3.3 Raster to vector conversion (cont.) Raster to polyline

  11. ___________________________________________________________ Advanced GIS UNT Geography  • 3.3 Raster to vector conversion (cont.) Raster to polygon

  12. ___________________________________________________________ Advanced GIS UNT Geography  • 3.4 Raster to ASCII conversion To convert a raster to an ASCII text file.

  13. ___________________________________________________________ Advanced GIS UNT Geography  Number of Columns Number of Rows X (lower left corner) Y (lower left corner) Cell Size NoData Value • 3.4 Raster to ASCII conversion (cont.) The header of an ASCII text file for a raster.

  14. ___________________________________________________________ Advanced GIS UNT Geography  • 3.4 Raster to ASCII conversion (cont.) An ASCII text file for a raster can be converted back to a raster.

  15. ___________________________________________________________ Advanced GIS UNT Geography  • 3.5 Raster to raster conversion Note: The GRID format includes an INFO folder shared with other grids, and is not very convenient for some other software packages. Grids can be converted into other formats.

  16. ___________________________________________________________ Advanced GIS UNT Geography  • 3.6 Raster to video conversion Note that the frame rate must be an integer. In this example, the input folder has 7 images, and the slowest rate is 1 frame per second (see next).

  17. ___________________________________________________________ Advanced GIS UNT Geography  • 3.6 Raster to video conversion (cont.)

  18. ___________________________________________________________ Advanced GIS UNT Geography  • 3.7 Cell statistics Cell statistics are on a cell-by-cell basis, which means the value at each location on the output raster is a function of the input values at the location. Analysis of cells and their neighbors in the same raster will be discussed in focal operations and zonal operations.

  19. ___________________________________________________________ Advanced GIS UNT Geography  6 4 4 3 3 3 5 2 5 4 4 4 2 2 4 3 2 5 3 5 2 4 4 4 3 2 4 3 4 2 7 3 5 3 3 4 3 3 3 3 4 2 3 2 2 3 3 5 4 3 2 5 2 3 2 5 4 3 4 3 3 2 2 2 3 5 3 2 5 4 4 3 3 3 4 6 3 3 2 3 5 4 6 2 5 3 5 2 5 2 4 2 3 3 4 3 • 3.7 Cell statistics (cont.) Each cell has a value for crop yield over a 20-year period. A total of 10 statistics can be obtained from the 20 raster layers: 1999 … • Majority • Minority • Maximum • Minimum • Mean • Median • Range • Sum • Standard Deviation • Variety … 1982 1981 1980

  20. ___________________________________________________________ Advanced GIS UNT Geography  • 3.7 Cell statistics (cont.)

  21. ___________________________________________________________ Advanced GIS UNT Geography  • 3.7 Cell statistics (cont.) Median: The median value is the middle value in a set of values. Half of all values are smaller than the median value and half are larger. When the data set contains an odd (uneven) set of numbers, the middle value is the median value. When the data set contains an even set of numbers, the middle two numbers are added and the sum is divided by two. That number is the median value. 1, 3, 4, 6, 7, 9, 12  Median value = 6 2, 3, 4, 5, 7, 8, 9, 10  Median Value = (5+7)/2 = 6

  22. ___________________________________________________________ Advanced GIS UNT Geography  • 3.7 Cell statistics (cont.) Why is median better than mean in some cases? Because mean and standard deviation are very sensitive to the most abnormal of values. Examples? For more information on standard deviation: http://en.wikipedia.org/wiki/Standard_deviation

  23. ___________________________________________________________ Advanced GIS UNT Geography  • 3.7 Cell statistics (cont.)

  24. ___________________________________________________________ Advanced GIS UNT Geography  • 3.7 Cell statistics (cont.) Example 1: Changes in vegetable fields

  25. ___________________________________________________________ Advanced GIS UNT Geography  • 3.7 Cell statistics (cont.) Example 2: Urban sprawl

  26. ___________________________________________________________ Advanced GIS UNT Geography  • Review • 3.1 Environment settings • 3.2 Vector to raster conversion • 3.3 Raster to vector conversion • 3.4 Raster to ASCII conversion • 3.5 Raster to raster conversion • 3.6 Raster to video conversion • 3.7 Cell statistics

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