- In ArcView, add the existing shape file or the geo-referenced image that you are going to reference the new image against.
- Activate the "Image Analyst Extension" (File / Extensions. checkmark "Image Analyst")
- Add a theme (click on the big Plus Icon or: View / Add a theme), chose "Image Analyst File" as file type and go along the path to the TIFF (or JPG) file. Highlight it and open it.
- Make the new TIFF-Image visible (that is, checkmark it) and move it to the bottom of all your layers (just drag and drop)
- Zoom in to the area where the new TIFF-Image should appear.
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Activate the theme with the TIFF-Image (just click on it once)
- Click the Align Tool once and be surprised!
- Zoom in to the area of a point which you can easily distinguish in both the TIFF-Image and in one of the already geo-referenced shapefile themes. Good points for this purpose are road intersections etc. (let's call such a point 'common point').
- Activate again the Align Tool and click on the first 'common point' on the TIFF-theme then click on the same point in the shapefile-theme. Do the same with as many other 'common points' you can find until you like the result. You need at least 4 points. This procedure is also called "rectifying" or "rubber-sheeting".
- Now that your scanned image is aligned properly you can create a new theme (View / Create a new theme) by tracing along any line or point of the scanned image as you see it on the screen.
- If you want to keep the TIFF image in the rubber-sheeted position you have save it explicitly: Theme / Save image as... (not Save Image)
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6 October 2000
The School of Architecture at UT Austin
Comments to: Barbara Parmenter