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Displacement Displacement
Displacement creates a Displacement item as a prelude to using Apply.
Paper maps and aerial photographs may be distorted when compared with vector maps created from accurate survey data, and if you scan a distorted paper map you will have a distorted map on screen. If you want to correct a distorted map, you may do so by a process known as rubber-sheeting.
To carry out this process, you must first create two or more Displacement items. Displacement items describe the required distortion of vector or raster data, using known control points.
You are first prompted to enter the old position, i.e. the position to be moved. Snap a position on a feature of the graphics which is either in the wrong place and should be distorted, or is in the correct place and should be pegged.
You will then be prompted to enter the new position. If the feature you identified is to be moved, you should snap to the new location for the feature. If it is to be fixed down without distortion, press the Enter key which uses the first position again. A line with an arrow at one end is displayed, to indicate the displacement required.
At least two Displacement items are required to create a Rubber Sheet item. However, to ensure that an accurate distortion takes place, you should provide as many Displacement items as possible.
Individual Displacement items may be edited by moving the handles at each end of the line.
When sufficient Displacement items have been defined, select them all and choose Create [Edit-Rubber Sheeting] to create a Rubber Sheet item.
This Rubber Sheet item may then be set as the current Rubber Sheet item using Set Transform [Edit-Rubber Sheeting]. The current Rubber Sheet item is used by the Rubber sheet command.
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