Plotting Maps to Scale

Q: How do I plot my coverage study to match a 1:250,000 scale map?

A: When you have the coverage map displayed on the screen, click the Print button.

  1. Select the option "Print to Scale"

  2. Select the scale value:

  3. Note that if the scale you want is not listed you can type in the scale value. Also, if you know the inches per mile (or centimeters per kilometer) for the map, you can enter that value.
  4. You should normally check the Preview Area box for reasons described below:

  5. To start the printing process, click the Print button:

  6. The program will use the scale information you have specified and the paper size for the printer selected to determine the area that will fit on the page at the desires scale. You must indicate the area you want to plot by clicking the center of the area.

  7. The area will be previewed on the drawing:

  8. If this is the area you want to print, click OK. If not, click Cancel:

  9. The map will be printed at the scale you selected.

Note several important considerations about plotting a map to scale:

The map projection you have selected will affect the plot. When a map projection is used to depict a spherical earth surface on a flat page, some distortion is always present. The nature and degree of the distortion depends on the map projection. For example, the Lamber Conformal Conic projection used for many maps of the continental United States (and supported in TAP) shows the true scale at two parallels (lines of latitude). The typical values for the standard parallels when plotting the continental U.S. are 33° and 45° N. TAP also allows you to select the Auto option in the Configuration | Map Projection menu. This option computes the standard parallels for the projection based on the area plotted, and places the standard parallels one-third of the range from the top and bottom of the plot. If you want to match typical USGS maps, you may want to un-check the Auto option for the Standard Parallels and set the values to are 33° and 45° N to match the standard maps as closely as possible.

Also note that the scale of the printed map is based on the central point you select to plot as described above. If you plot the same general area multiple times you should select the same central point to match the scaling on each plot.

 

 

Copyright 1999 by SoftWright LLC