Basic operations performed on raster in ArcGIS

1. Basics Operations on Raster
Prof. Dr. Sajid Rashid Ahmad
sajidpu@yahoo.com
Atiqa Ijaz Khan _ Demonstrator
atiqa_ss09@yahoo.com

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To adjust the symbology
Giving information about the
raster and its properties.
Under TOC > Layer Properties

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
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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.
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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”.

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Result of Unique Symbology on Raster
On moving the cursor
over the raster, it’ll show
the Value from the
attribute table as created.

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Classified Symbology
NO Data

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Result of Unique Symbology on Raster
NO
data
values

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9Upper Right:
Stretched Symbology
Lower Right:
Result of Stretched Symbology on Raster

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Upper Right:
Discrete Symbology
Lower Right:
Result of Discrete Symbology on Raster

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.
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12Create Pyramids
Pyramids Re-sampling
Techniques

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Re-sampling Technique
Arc Toolbox > Data Management
> Raster > Raster Processing >
Resample

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.
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Without Hill Shade Effect
Un-check the hill shade effect

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With Hill Shade Effect
Check the hill shade effect

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.
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Extraction by Mask
Input the Raster layer
Input the Shapefile
Save the output raster

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Input raster layer
and shapefile
Output Extracted
raster
Pakistan Raster Layer
Output
Punjab Raster
Punjab Shapefile

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