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Basics Operations on Raster Prof. Dr. Sajid Rashid Ahmad [email protected] Atiqa Ijaz Khan _ Demonstrator [email protected]

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Basics Operations on Raster

Prof. Dr. Sajid Rashid Ahmad

[email protected]

Atiqa Ijaz Khan _ Demonstrator

[email protected]

Tuesday, March 3, 2015Institute of Geology, University of the Punjab

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To adjust the symbology

Giving information about the

raster and its properties.

Under TOC > Layer Properties

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

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Types of Symbology for Raster

• Unique Values:

• Each value in raster will be given a unique value. Such as, soil types or land use. Itshould 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

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Tuesday, March 3, 2015Institute of Geology, University of the Punjab

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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”.

Tuesday, March 3, 2015Institute of Geology, University of the Punjab

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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.

Tuesday, March 3, 2015Institute of Geology, University of the Punjab

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Classified Symbology

NO Data

Tuesday, March 3, 2015Institute of Geology, University of the Punjab

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Result of Unique Symbology on Raster

NO

data

values

Tuesday, March 3, 2015Institute of Geology, University of the Punjab

9Upper Right:

Stretched Symbology

Lower Right:

Result of Stretched Symbology on Raster

Tuesday, March 3, 2015Institute of Geology, University of the Punjab

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Upper Right:

Discrete Symbology

Lower Right:

Result of Discrete Symbology on Raster

Building Pyramids of Raster

• As the raster dataset is added to the ArcGIS, it’ll give the option of buildingpyramids 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 asthat 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

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Tuesday, March 3, 2015Institute of Geology, University of the Punjab

12Create Pyramids

Pyramids Re-sampling

Techniques

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Re-sampling Technique

Arc Toolbox > Data Management

> Raster > Raster Processing >

Resample

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

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Tuesday, March 3, 2015Institute of Geology, University of the Punjab

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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

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

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Tuesday, March 3, 2015Institute of Geology, University of the Punjab

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Extraction by Mask

Input the Raster layer

Input the Shapefile

Save the output raster

Tuesday, March 3, 2015Institute of Geology, University of the Punjab

19Input raster layer

and shapefile

Output Extracted

raster

Pakistan Raster Layer

Output

Punjab Raster

Punjab Shapefile

Tuesday, March 3, 2015Institute of Geology, University of the Punjab

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