WETMAAP Skill 2
Fort Clatsop: Element 2
Skill
2: Scale Determination
Element
2: Determining Scale of 2000
Aerial Photograph
Materials:
1:24,000 scale Warrenton-Astoria Topographic Quadrangle
2000 Aerial Photograph of study site
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 2000 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 2000 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 2000 aerial
photograph. Make a mark on the aerial photograph 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 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?