membuat georeferen arcmap

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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 pointinformation 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.

InArcCatalog,browse to the folder your dataset is contained in.

Right-click the raster dataset and select Properties

Click the Spatial Referencetab in the Raster Dataset Propertieswindow

ClickEditin 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 Systemwindow and browsing

to the datas projection system.

Map projection: UTMDatum: ED 1950

Zone: 36


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ClickOKto accept the current projection assignment.

ClickOKto close the Raster Dataset Propertieswindow

You can close the ArcCatalog window

OpenArcMapby clicking Start > All Programs > ArcGIS > ArcMap.

ClickAdd Data

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

ClickYesin the Create Pyramids for Data s Name

ClickView-Toolbars-Georeferencing Toolbar

Zoom inthe first coordinate on your raster data

Click theAdd Controls Pointto add control point

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

add the first coordinate in the link.

ClickView Link Table

X: 34 0000

Y: 464 0000


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Type in theX Mapand Y Mapvalues for the first coordinate point

ClickFull Extentto see the whole raster data on the screen

Zoom inthe second coordinate on your raster data

ClickAdd Control Pointto add control point


add the second coordinate in the link

Type in theX Mapand Y Mapvalues for the second coordinate point


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ClickFull Extentto see whole your raster data on the screen

Zoom inthe third coordinate on your raster data

ClickAdd Control Pointto add control point


add the third coordinate in the link

Type in theX Mapand Y Mapvalues for the third coordinate point


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ClickFull Extentto see whole your raster data on the screen

Zoom inthe third coordinate on your raster data

ClickAdd Controls Pointto add control point


add the fourth coordinate in the link

Type in theX Mapand Y Mapvalues for the fourth coordinate point


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You can checktotal residual

values in here


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ClickGeoreferencingand clickRectifyto save the transformation information with

the raster.

Accept Cell Sizevalue

ClickResample Type >Nearest neighbor (for discrete data) generally this is

the best choice.

Type the rasters new name in the Name box

ClickSave

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

contains the coordinate information.

ClickAdd Data

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

The georeferenced raster is added to the map.

ClickYeswhen prompted to Create Pyramids.


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See that the raster is

now in the propercoordinate space.


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GEOREFERENCING USING A GIS LAYER

OpenArcMapby clicking Start > All Programs > ArcGIS > ArcMap

ClickAdd Data, and browse to the GIS layer to which you will georeference theraster 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 Layersin the table of contents.

Select Properties,

Select the Coordinate Systemtab in the Data Frame Propertieswindow.

In the Select a Coordinate System window, clickPredefined, and set the projection

to the same as the source map.

ClickOKin the Data Frame Propertieswindow,


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ClickAdd Data,

Browse to the raster file from theAdd Datawindow and select it,

ClickOpento add the source image to ArcMap.

At the ArcMap message:

ClickYes,

At the ArcMap message:

ClickOK,

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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ClickView > Toolbars > Georeferencing Toolbar,

Zoom the map to the general area your image covers.ClickGeoreferencingand clickFit 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 Displaytab in the Layer Propertieswindow,

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

ClickOK.

Source image at the top ofthe 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 into the first matching feature on your source image,

ClickAdd Control Pointto 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 outuntil the same feature on the GIS layer is visible.

Zoom into the same feature on the GIS layer.

ClickAdd 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.

ClickView 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 po int


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Zoom into the second matching feature on your source data,

ClickAdd Control Pointto 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 into the second matching feature on your GIS layer,

ClickAdd Control Point,

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

second coordinate.

ClickView Link Table,

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

The second imagecontrol point


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


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ClickGeoreferencingand clickRectifyto save,

Accept Cell Sizevalue,

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

is the best choice.

Type the name of the georeferenced raster in the Namebox,

1. Poin t

2. Poin t

3. Poin t

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.

ClickAdd Data,

Browse to the newly created raster in theAdd Datawindow,

Select it, and clickOpen,

ClickYesin the Create Pyramids, dialog box, and the georeferenced raster will be

added to the map.

membuat georeferen arcmap

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