1 Georeferencing/Rectifying Images in ArcMap 9.x 1)Open ArcMap and turn on the Georeference Toolbar and the Effects Toolbar under VIEW | TOOLBARS. 2)Set the coordinate system for your Data Frame (right click | Properties | Coordinate System tab). 3)Add some reference data layers to the Data Frame (roads, air photos, PLS data, etc). 4)Add the image to rectify as a data layer. 5)Zoom to an identifiable location on the image to be rectified. 6)In the Georeferencing Toolbar Select the layer to be georeferenced/rectified (must be a TIF or JPG). 7)Click the Control Point button, then click on the rectify image to place a control point (green X). 8)Turn off the rectify layer.

2 Georeferencing/Rectifying Images in ArcMap 9.x 9)Zoom to the same place in the reference data and place a control point link (red X). The image to rectify should now be anchored to the reference data. 10)Adjust the transparency of the layer you are rectifying. In the Effects toolbar select the rectify layer, then click the transparency button and select a midway value on the sliding scale. 11)Use the Control Point button to place a second control point (green X) on the rectify image. 12)Use the Swipe button on the Effects Toolbar to pull the rectify image away from the reference data underneath. Click the button, then hold your cursor over the screen. When you see a black arrow, hold your left mouse button down and drag the rectify image in the direction of the arrow.

3 Georeferencing/Rectifying Images in ArcMap 9.x 13)Zoom to the same place in the reference data and place a control point link (red X). 14)Repeat steps at least twice more, placing control points evenly throughout the image. An average of 6-10 control points is adequate for most rectifications. 15)Check your Root Means Square Error (RMSE). In the Georeference Toolbar click the Link Table button to open it. Note:RMSE is more of a measure of the quality of the image than it is a measure of the quality of the control point placement. The purpose of ground control points is to identify features common to both images. If you are confident that you have selected the same feature on both the reference and image sources, leave the point as is. Adjusting a point off a true location to achieve better RMSE makes the overall rectification worse. An RMSE that is artificially low due to this practice will likely produce poorer results.

4 Georeferencing/Rectifying Images in ArcMap 9.x 16)Examine the residual error of each control point. Is there one value significantly higher than the others? Do you know that you made a mistake in placing that point? RMSE is relational – one point “tugs” at and therefore changes the RMSE of all others. Deleting one or more poorly placed points (and perhaps placing new ones) may reduce the total RMS error and improve the overall rectification... Highlight the record in the link table and press [DEL] on your keyboard to delete it. 17)If you have enough points placed, you can select the order of transformation you prefer. The georeferenced image will automatically reflect the selection. 18)When you are satisfied with the points you’ve placed, click Save in the Link Table to save the points to a file for later reference.

5 Georeferencing/Rectifying Images in ArcMap 9.x 19)Drop down the Georeferencing Toolbar menu and choose Rectify. 20)In most cases, accept the cell size and resample type, give the output file a name and saving place, then click Save. The image will be processed. 21)Add the newly rectified image as a data layer. 22)Should the newly rectified image need further rectification, simply repeat steps 5-21 (rather than having to begin from scratch).