WETMAAP Skill 2
Avery and Weeks Islands: Element 2

Skill 2: Scale Determination
Element 2: Determining Scale of 1995 Aerial Photograph

 Materials:
            1963/80 Delcambre Topographic Quadrangle   
            1995 Avery Island Aerial Photograph
            9" x 9" clear film overlay
            color marker pens
            ultra fine black marker pen
            ruler                                                       drafting tape
            calculator                                                 Reference Manual

 Exercise:
         1.      Tape the 9" x 9" clear film overlay on top of the 1995 aerial photography.

          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 photography.

         3.      Using the 1:24,000 scale topographic map and the Black pen, locate the four corners of the study site on the 1995 aerial photography.

           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 on the 1:24,000 scale topographic map at least four inches apart.

                              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 1995 aerial photograph.  Make a mark on the aerial photograph for each l                         location.

              7.      Measure the distance between the two points on the 1:24,000 scale topographic map with the ruler.

                        _________________      What is the distance in inches?

            8.      Measure the distance between the two points on the 1995 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?