WETMAAP Skill 2
San Pedro - Element 2

Skill 2:                    Scale Determination
Element 2:              Determining the Scale of the 1999 Aerial Photograph

 Materials:

            1994 1:24,000 scale USGS Lewis Springs-Tomestone SE Topographic Quadrangle
            1999 Aerial Photograph of study site
            9" x 9" clear film overlay
            color pens
            ruler
            drafting tape
            calculator
            Reference Manual

 Exercise:

      1.      Tape the 9" x 9" clear film overlay on top of the 1999 aerial photograph.

            2.   Use the black pen to make four marks on each fiducial.

                             Hint: The fiducial is a yellow dot or cross-hair along each of the four sides of the aerial photograph.

          3.       Using the1983/821:24,000 scale USGS Lewis Springs-Tomestone SE Topographic Quadrangle and the black pen, locate the four

                        corners of the study site on the 1999 aerial photograph.

             4.   Use the ruler and the black pen; link the four corners of the study site to make a complete boundary.

           5.      Identify two points at least four inches apart on the1983/82 1:24,000 scale USGS Lewis Springs-Tomestone SE Topographic Quadrangle

                              Hint: It is best to identify and use cultural features, but if not enough are available, use two natural feature points that do not appear to have changed.

             6.      Identify the exact same two features from the topographic map on the 1999 aerial photograph.  Make a mark on the aerial photograph for each location.

             7.      Measure the distance between the two points on the the1983/82 1:24,000 scale USGS Lewis Springs-Tomestone SE  Topographic Quadrangle
                                    with the ruler.

            ____________________      What is the distance in inches?

            8.      Measure the distance between the two points on the 1999 aerial photograph with the ruler.

                              ____________________   What is the distance in inches?

            9.      Using the calculator and "Scale Determination" section of the Reference Manual, determine the scale of the aerial photograph.

           ____________________      What is the scale that you calculated?