## Defining Model Scale

Model scale is defined by dividing the length of scaled model side into its corresponding unscaled length. Make sure scaled and unscaled length have the same units of measurement. The resulting quotient is the scale factor. We assume that the scale is the same in all directions.

The unscaled measurement can be derived from metrics in Google Earth , Global Mapper, or other source.

An initial scale factor is often adjusted by rounding. For example, if your model is to be 24" x 36" and the 36" side represnts 8 miles, the scale factor is (8 x 5280 x 12)/36 = 14080. The scale is 1:14080 or 1"= 1173.3'. You may want to change the scale to 1" = 1200' or 1" = 1000' to more convieniently measure distance on the finished model.

## Scale and Available Shape and Image Data

Pixel Width                          Grid Spacing

Scale                        IMAGE 500 dpi                 SHAPE 100 points/inch
1:120000  1” = 10000’        20’      6.09 meters             100’       30.480 meters
1:48000    1” = 4000’          8’      2.44 meters               40’       12.192 meters
1:24000    1” = 2000’          4’       1.22 meters                20’       6.096 meters
1:12000     1” = 1000’          2’       .61 meters                  10’       3.048 meters
1:6000      1” = 500’            1’       .30 meters                  5’        1.524 meters
1:2400      1” = 200’            .4’      .12 meters                   2’        .610 meters

The table shows image and shape resolution for some common scales. Shape grid data and image pixel data need to be available at high enough resolution to support making the model at the selected scale.

Example

if the model scale is 1" = 200', image resolution should be .12 meters to give 500 pixels per inch resolution for laser marking the image. The USGS .15 meter image (if available) would be good. For the shape data grid spacing of 2 feet is desired, one meter USGS or state elevation data (if available) would be good.