This question is most frequently related to files created in a Computer Aided Design (CAD) program.
An engineering scale, expressing scale as an inch on the map being equal to a number of feet or meters on the ground, must be converted to a proportional scale when the CAD data is to be used in ArcMap.
To convert the following engineering scale:
1" = 400' for use in ArcMap,
multiply the number of feet, in this case 400, by 12 to convert the feet to inches.
This yields a scale in ArcMap of 1:4800.
This is a proportional scale, in which the units on both sides of the colon (:) are the same.
1" = 4800"
1' = 4800'
1 meter = 4800 meters
If the engineering scale is expressed as
1" = 100 meters,
multiply the number of meters by 39.37, the number of inches in a meter. The proportional scale would then be: