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?