georeferencing image in arcmap

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Georeferencing Images in ArcMap CGA, March 21, 2008 1 GEOREFERENCING IMAGES IN ARCMAP The Georeferencing process allows for creation and storage of control point information that assigns coordinates to raster datasets (.tif, .jpeg, .img, GRID, etc.) for display of the dataset in its correct geographic location. GEOREFERENCING USING MAP COORDINATES Start ArcCatalog by clicking Start > All Programs > ArcGIS > ArcCatalog, or click the icon in ArcMap. In ArcCatalog, browse to the folder your dataset is contained in. Right-click the raster dataset and select Properties Click the Spatial Reference tab in the Raster Dataset Properties window Click Edit in the same window to choose the correct map projection. Find the proper projection / coordinate system info from your map and assign it to the raster by clicking Select in the XY Coordinate System window and browsing to the data’s projection system. Map projection: UTM Datum: ED 1950 Zone: 36

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Page 1: Georeferencing Image in ArcMap

Georeferencing Images in ArcMap CGA, March 21, 2008

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GEOREFERENCING IMAGES IN ARCMAP

The Georeferencing process allows for creation and storage of control point

information that assigns coordinates to raster datasets (.tif, .jpeg, .img, GRID, etc.)

for display of the dataset in its correct geographic location.

GEOREFERENCING USING MAP COORDINATES

Start ArcCatalog by clicking Start > All Programs > ArcGIS > ArcCatalog, or

click the icon in ArcMap.

In ArcCatalog, browse to the folder your dataset is contained in.

Right-click the raster dataset and select Properties

Click the Spatial Reference tab in the Raster Dataset Properties window

Click Edit in the same window to choose the correct map projection.

Find the proper projection / coordinate system info from your map and assign it to

the raster by clicking Select in the XY Coordinate System window and browsing

to the data’s projection system.

Map projection: UTM Datum: ED 1950 Zone: 36

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Click OK to accept the current projection assignment.

Click OK to close the Raster Dataset Properties window

You can close the ArcCatalog window

Open ArcMap by clicking Start > All Programs > ArcGIS > ArcMap.

Click Add Data

Browse to your raster, click on it, and and click Open to add it to the map.

Click Yes in the Create Pyramids for Data’ s Name

Click View-Toolbars-Georeferencing Toolbar

Zoom in the first coordinate on your raster data

Click the Add Controls Point to add control point

Click the left mouse button over the known location in the unreferenced image to

add the first coordinate in the link.

Click View Link Table

X: 34 0000 Y: 464 0000

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Type in the X Map and Y Map values for the first coordinate point

Click Full Extent to see the whole raster data on the screen

Zoom in the second coordinate on your raster data

Click Add Control Point to add control point

Click the left mouse button over the known location in the unreferenced image to

add the second coordinate in the link

Type in the X Map and Y Map values for the second coordinate point

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Click Full Extent to see whole your raster data on the screen

Zoom in the third coordinate on your raster data

Click Add Control Point to add control point

Click the left mouse button over the known location in the unreferenced image to

add the third coordinate in the link

Type in the X Map and Y Map values for the third coordinate point

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Click Full Extent to see whole your raster data on the screen

Zoom in the third coordinate on your raster data

Click Add Controls Point to add control point

Click the left mouse button over the known location in the unreferenced image to

add the fourth coordinate in the link

Type in the X Map and Y Map values for the fourth coordinate point

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You can check total residual values in here

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Click Georeferencing and click Rectify to save the transformation information with

the raster.

Accept Cell Size value

Click Resample Type >Nearest neighbor (for discrete data) – generally this is

the best choice.

Type the raster’s new name in the Name box

Click Save

This creates a new file with the name specified, and an associated .aux file that

contains the coordinate information.

Click Add Data

Browse to the new raster file, click it, and click Open

The georeferenced raster is added to the map.

Click Yes when prompted to Create Pyramids.

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See that the raster is now in the proper coordinate space.

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GEOREFERENCING USING A GIS LAYER

Open ArcMap by clicking Start > All Programs > ArcGIS > ArcMap

Click Add Data, and browse to the GIS layer to which you will georeference the

raster data, select it, and click Open to add it to the map.

Notice from the coordinate display that the GIS layer is georeferenced already

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Examine the source image that needs georeferencing for a projection definition.

Click the right mouse button on Layers in the table of contents.

Select Properties,

Select the Coordinate System tab in the Data Frame Properties window.

In the Select a Coordinate System window, click Predefined, and set the projection

to the same as the source map.

Click OK in the Data Frame Properties window,

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Click Add Data,

Browse to the raster file from the Add Data window and select it,

Click Open to add the source image to ArcMap.

At the ArcMap message:

Click Yes,

At the ArcMap message:

Click OK,

The image is added to the bottom of the table of contents.

Click and drag the source image to the top of the table of contents.

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Click View > Toolbars > Georeferencing Toolbar,

Zoom the map to the general area your image covers.

Click Georeferencing and click Fit To Display,

This will display the source image in the same area you are zoomed into.

Click the right mouse button on the source image in the table of content,

Select Properties,

Click the Display tab in the Layer Properties window,

Type 30 in the Transparency to display the image with a 30% transparency.

Click OK.

Source image at the top of the table of contents

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Now it is time to match features in the image with those on the GIS layer. A

minimum of 4 identical points are required, preferably one on each corner of the

map. Adding more than 4 may improve the georeferencing result.

Zoom in to the first matching feature on your source image,

Click Add Control Point to add a control point

Click the left mouse button on the feature in the image to add the first coordinate.

When adding control points, choose discrete features visible in both the image and

GIS layer. For example: road intersections, narrow tips of islands, etc. Zoom in and

click as accurately as you can when adding control points.

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Zoom out until the same feature on the GIS layer is visible.

Zoom in to the same feature on the GIS layer.

Click Add Control Point,

Click the left mouse button on the same feature in the GIS layer to assign the first

coordinate.

After clicking, the source image will move, and align itself with the GIS layer based

on the control point you added.

Click View Link Table,

The first control point appears on the list in the View Link Table, with the map

coordinates automatically added.

The first image control point

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Zoom in to the second matching feature on your source data,

Click Add Control Point to add a control point,

Click the left mouse button over the feature in the unreferenced image to add the

second coordinate.

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Zoom out until the same feature on the GIS layer is visible.

Zoom in to the second matching feature on your GIS layer,

Click Add Control Point,

Click the left mouse button over the same feature in the referenced image to add the

second coordinate.

Click View Link Table,

The second control point appears on the list in the View Link Table.

The second image control point

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Repeat this procedure to add a third and fourth control point.

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Click Georeferencing and click Rectify to save,

Accept Cell Size value,

Choose Resample Type >Nearest neighbor (for discrete data) – generally this

is the best choice.

Type the name of the georeferenced raster in the Name box,

1. Point 2. Point

3. Point

4. Point

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Click Save and a new file with the name specified will be created, along with an

associated .aux file that contains the coordinate information.

Click Add Data,

Browse to the newly created raster in the Add Data window,

Select it, and click Open,

Click Yes in the Create Pyramids, dialog box, and the georeferenced raster will be

added to the map.