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Lab_11_Raster

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Basic operations performed on raster in ArcGIS

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Lab_11_Raster

  1. 1. Basics Operations on Raster Prof. Dr. Sajid Rashid Ahmad sajidpu@yahoo.com Atiqa Ijaz Khan _ Demonstrator atiqa_ss09@yahoo.com
  2. 2. Tuesday, March 3, 2015Institute of Geology, University of the Punjab 2 To adjust the symbology Giving information about the raster and its properties. Under TOC > Layer Properties
  3. 3. Symbology on Raster • In the Table of Contents > Properties > Symbology. • Other options available are: • Display NO data • Hill shade effect • Background color etc. • Symbology offers • Unique values • Classified • Stretched • Discrete Color Tuesday, March 3, 2015Institute of Geology, University of the Punjab 3
  4. 4. Types of Symbology for Raster • Unique Values: • Each value in raster will be given a unique value. Such as, soil types or land use. It should not increase above the 2,048 entries. • Classified: • Color transition are not precise, but range can be shown easily. • Stretched: • Discrete: • Each value of raster cell is given a unique color, until maximum number of colors. This is good for larger datasets. Tuesday, March 3, 2015Institute of Geology, University of the Punjab 4
  5. 5. Tuesday, March 3, 2015Institute of Geology, University of the Punjab 5 Unique Values Symbology 1. As the given raster dataset is without attribute table, (in normal condition), on clicking the “Unique Values” from the Symbology, it’ll ask to create Attribute table, so to pick up the unique raster values. On clicking it’ll generate the table, so also that for symbology of it. 2. It’ll take time on creating it on the base of size of datasets. 3. It’ll be created for one in a time. 4. Attribute table can be accessed as usual. 5. It’s results are more likely similar to “Discrete Color”.
  6. 6. Tuesday, March 3, 2015Institute of Geology, University of the Punjab 6 Result of Unique Symbology on Raster On moving the cursor over the raster, it’ll show the Value from the attribute table as created.
  7. 7. Tuesday, March 3, 2015Institute of Geology, University of the Punjab 7 Classified Symbology NO Data
  8. 8. Tuesday, March 3, 2015Institute of Geology, University of the Punjab 8 Result of Unique Symbology on Raster NO data values
  9. 9. Tuesday, March 3, 2015Institute of Geology, University of the Punjab 9Upper Right: Stretched Symbology Lower Right: Result of Stretched Symbology on Raster
  10. 10. Tuesday, March 3, 2015Institute of Geology, University of the Punjab 10 Upper Right: Discrete Symbology Lower Right: Result of Discrete Symbology on Raster
  11. 11. Building Pyramids of Raster • As the raster dataset is added to the ArcGIS, it’ll give the option of building pyramids of that raster. • Select the type of re-sampling technique. • OK. • Pyramids are added as .ovr file with the raster dataset, having the same name as that of the file. • It’ll take time on building according to the size of the raster. Tuesday, March 3, 2015Institute of Geology, University of the Punjab 11
  12. 12. Tuesday, March 3, 2015Institute of Geology, University of the Punjab 12Create Pyramids Pyramids Re-sampling Techniques
  13. 13. Tuesday, March 3, 2015Institute of Geology, University of the Punjab 13 Re-sampling Technique Arc Toolbox > Data Management > Raster > Raster Processing > Resample
  14. 14. Hill Shade • TOC > Layer Properties > Symbology > Stretched/Classified. • Check the box. • OK. • 3D Analyst Tools > Raster Surface > Hill Shade. • Spatial Analyst Tools > Surface > Hill Shade. Tuesday, March 3, 2015Institute of Geology, University of the Punjab 14
  15. 15. Tuesday, March 3, 2015Institute of Geology, University of the Punjab 15 Without Hill Shade Effect Un-check the hill shade effect
  16. 16. Tuesday, March 3, 2015Institute of Geology, University of the Punjab 16 With Hill Shade Effect Check the hill shade effect
  17. 17. Extracted Raster by Mask • Portion of raster can be extracted by the boundary of shapefile. • This can be performed as: • Arc Toolbox > Spatial Analyst tool > Extraction > Extracted by Mask. • Other options are: • By Attributes • Point • Polygon • Circle • Rectangle, etc. Tuesday, March 3, 2015Institute of Geology, University of the Punjab 17
  18. 18. Tuesday, March 3, 2015Institute of Geology, University of the Punjab 18 Extraction by Mask Input the Raster layer Input the Shapefile Save the output raster
  19. 19. Tuesday, March 3, 2015Institute of Geology, University of the Punjab 19 Input raster layer and shapefile Output Extracted raster Pakistan Raster Layer Output Punjab Raster Punjab Shapefile
  20. 20. Tuesday, March 3, 2015Institute of Geology, University of the Punjab 20

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