WETMAAP Skill 2
Weweantic River  - Element 2

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

Materials:

1:25,000 scale 1977-1972 Snipatuit Pond – Wareham; 1977-1974 Plympton – Plymouth, Mass, USGS Topographic Quadrangles
1995 Aerial Photograph of study site
(1) 9" x 9" clear film overlays
color marker pens
ultra fine black marker pen
ruler drafting tape
calculator Reference Manual

Exercise:

1. Tape one of the 9" x 9" clear film overlays on top of each of the 1995 aerial photographs

2. Use the Black pen to make four marks; one for each fiducial on each photo.

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

3. Using the 1:25,000 scale USGS Topographic Quadrangle and the Black pen, locate the four corners of the study site on the 1995 aerial photograph.

Hint: Study site overlaps on both photos.

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 1:25,000 scale USGS Topographic Quadrangle 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 USGS Topographic Quadrangle on the 1995 aerial photographs. Make a mark on the aerial photographs for each location.

Hint: It is best to have the two points on the same photo.

7. Measure the distance between the two points on the 1:25,000 scale USGS Topographic Quadrangle with the ruler.

_________________ What is the distance in inches?

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