WETMAAP Skill 2
Texas City/Virginia Point: Element 2

Skill 2: Scale Determination
Element 2: Determining the Scale of the 1992b Aerial Photograph

Materials:

1:24,000 1994 Virginia Point Topographic Quadrangle

1992b Aerial Photography 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 1992b 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 photograph.

3. Using the 1:24,000 1994 Virginia Point quuadrangle and the black pen, locate the four corners of the study site.

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: Identify and use cultural features.

6. Identify the exact same cultural features from the topographic map on the 1992b aerial photography. Make a mark on the aerial photography for each 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 1992b aerial photography 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 photography.

What is the scale that you calculated?