ArcMap > Creating maps
About World files |
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Release 9.1
Last modified December 7, 2006 |
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A World file is a text file (.wld) containing one or two pairs of x,y coordinates. The first pair of x,y coordinates is the actual x,y location of any known control point in your drawing file. The second pair of x,y coordinates is a new location in geographic space where you would want the CAD drawing control point to be in ArcMap.
The World file format is as follows:
<x,y location in CAD drawing> <space> <x,y location in geographic space>
The World file must have the .wld extension and cannot have more than two lines in the above format. ArcMap automatically applies the World file when it finds a valid file name with the same prefix as the drawing file name in the same folder. For example, suppose you've stored sample.dwg and sample.wld files in the same folder. When you add layers from sample.dwg, ArcMap automatically uses the sample.wld file for coordinate transformations.
Consider the following pairs of coordinates in your World file:
25.0,60.0 25000.0,60000.0
When you apply the above World file, it will shift the CAD layer location (25.0,60.0) to a new location (25000.0,60000.0) in the view.
Learn how to apply a coordinate transformation to a CAD layer by World file
Suppose you have two known control points in your CAD layer and you know the new location for one of these two control points. You want to apply a transformation such that your CAD layer will:
- Shift all features to the new known location.
- Uniformly apply a scale factor of 100 to all features in the theme.
- Rotate all theme features 90 degrees.
You can use the following formula to calculate the new x,y location for the second control point:
x' = Ax + By + C
y' = -Bx + Ay + D
Where
x' = calculated x-value for the second control point
y' = calculated y-value for the second control point
x = x-coordinate of the second CAD control point
y = y-coordinate of the second CAD control point
A = s * cos(@) B = s * sin(@)
C = x-coordinate of the known new location (translation in x direction)
D = y-coordinate of the known new location (translation in y direction)
s = scale change (scale factor such as 1, 1.5, and so on)
@ = rotation angle
In the above example, suppose your first control point in your CAD layer is (0,0) and the second control point is (12.0,9.0). The known new location for the first control point is (1200.0,1300.0). The scale factor is 100, and the drawing rotation angle is 90 degrees.
Using the above formula, you can calculate the new x,y coordinates for the second control point as shown below:
x = 12
y = 9
A = 100 * cos (90) = 0
B = 100 * sin (90) = 100
C = 1200
D = 1300
x' = 0 + 900 + 1200 = 2100
y' = -1200 + 0 + 1300 = 100
Therefore, the World file for this example will have values as shown below:
0,0 1200.0,1300.0
12.0,9.0 2100.0,100.0