Skill 2: Scale Determination
Element 2: Determining the Scale of the 1988 Aerial Photograph
 
Materials:
            1997/1993 1:24,000 scale  San Mateo, CA / Redwood City, CA, USGS  Topographic Quadrangle
            2000 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 2000 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 the1997/1993 1:24,000 scale  San Mateo, CA / Redwood City, CA,USGS Topographic Quadrangle and the black pen, locate the four corners of the study site on the 2000 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 the 1997/1993 1:24,000 scale  San Mateo, CA / Redwood City, CA, USGS 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 2000 aerial photograph.  Make a mark on the aerial photograph for each location.
 
      7.   Measure the distance between the two points on the the1997/1993 1:24,000 scale  San Mateo, CA / Redwood City, CA USGS Topographic Quadrangle with the ruler.
 
                 ____________________  What is the distance in inches?
           
       8.   Measure the distance between the two points on the 2000 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?