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with degrees from the University of Northern Colorado, the US Naval postgraduate School, and the University of Colorado at Denver. He worked as a systems engineer on the FAA's Advanced Automation System, the United Technology Advanced Group Rapid Transit System, and Dish TV audio, video and smart hand held remote control systems.

 

USGS elevation data sets have grid sample spacing of 1 meter, 3 meter, 10 meter, 30 meter, 100 meter. Calculatiing the scale range for 20 and 200 source data points per inch gives the following table. Select your source data set grid resolution based on the model scale..

 

USGS 1 meter data, model scale: 1" = 66'     to    1" = 656'.

USGS 3 meter data, model scale: 1" = 197'    to    1" = 1969'.

USGS 10 meter data, model scale:  1" = 656'   to    1" = 6562'.

USGS 30 meter data, model scale:  1" = 1967'  to    1" = 19685' .

USGS 100 meter data, model scale:  1" = 6562'  to    1" = 65617' .

 

 

 

 

Use the USGS TNM Viewer to check image coverage for your area of interest. Most of the US is covered by 1 meter ortho images.

 

 

 

Determine the model scale factor by dividing the length of one side of the model in inches into the unscaled length of the same side (also in inches).

 

 

Westwater Canyon, Utah, popular rafting area.

Shape USGS 10 meter data.

Image USGS1 1 meter orthoimagery.

15" x 48" x .83", scale 1:30000, 1.2 vertical exaggeration.

15 pound foam, tool diameter .03".

 

 

 

Submitting a CAD File General Considerations

Scale the model and translate it to the 1st quadrant of the Cartesion coordinate plane. From top down view, draw the smallest box around the model with sides of interger length in inches and  the lower left corner located at the origon. The box gives the length and width of the model in inches. The model should be contained in the box.

 

Verify model width, length and height are less than 48" x 96" x 7". Usually 1/2" to 1" or more model from the model low is allowed for the model base. The exact model base thickness often remains unspecified and depends on the left over thickness of material after cutting.

 

 

Scale and Available Shape and Image Data

 

In order to make the model the scale you choose must be supported by available shape and image data. The table shows image and shape resolution for some common scales.

 

 

                                              Pixel Width                          Grid Spacing                                Grid Spacing

            Scale                        IMAGE 500 dpi                 SHAPE 100 points/inch                SHAPE 200 points/inch
1:120000  1” = 10000’        20’      6.09 meters             100’       30.480 meters                   50’      15.240 meters
1:48000    1” = 4000’          8’      2.44 meters               40’       12.192 meters                     20’        6.096 meters
1:24000    1” = 2000’          4’       1.22 meters                20’       6.096 meters                     10’        3.048 meters
1:12000     1” = 1000’          2’       .61 meters                  10’       3.048 meters                      5’        1.524 meters
1:6000      1” = 500’            1’       .30 meters                  5’        1.524 meters                     2.5’          .762 meters
1:2400      1” = 200’            .4’      .12 meters                   2’        .610 meters                         1’          .305 meters

 

If you choose a scale of 1" = 2000', each pixel in the 500 dots per inch image is 1.22 meters wide. Ideally, you would want your image source to have at least this resolution. USGS 1 meter orthoimage data is good for this scale.

 

USGS .15 meter orthoimage data is good for a 1" = 200' scale model.