Map/ Air Photo Scale - Practice Questions

Answer the following questions in a neat and organized fashion.

Conversions:

1 inch = 2.54 cm

12 in = 1 foot

63,360 in = 1 mile

10,000m2 = 1 ha

1 m = 100 cm

1 km = 1,000 m

Remember:

map scale = 1 / x = map dist. / real world dist.

photo scale = 1 / x = photo dist. / real world dist. = focal length / flying ht above ground

altitude = flying ht (above ground) + elevation

1.    What is the length in cm of one km on a 1:25,000?

2.    What is the length in cm of 2 miles on a 1: 20,000 map?

3.    What is the length in cm of 2 km on a 1” = ½ mile photo?

4.    What is the length of 1.9 km on a 1” = ½ mile photo?  What is the scale of this photo expressed as a representative fraction?

5.   The distance between two features on a photo is 11.5 cm and the corresponding distance is 5 km on the ground.  What is the approximate scale of the photo?

6.    A map scale is 1 cm = 750 m and a photo covers a portion of the map area.  The distance between two road intersections measures 9.8 cm on the photo and 5.0 cm on the map.  Determine the scale of the photo.

7.    A distance of 11.5 cm is measured on a photograph for which the focal length is 305 mm and the corresponding distance of 3 cm is measured on a 1: 50,000 map.  The area in question lies at 433 m above sea level.  Determine the altitude above sea level of the aircraft when the photo was taken.

8.   What is the scale of a vertical photo, if the focal length of the camera is 300 mm, the flight altitude is 15,000 ft above sea level and the ground elevation is 650 m.

9.   On an old air photo you can see a large snag that is 4.1 cm from a road intersection.  The scale of the photo is 1” : 20 chains.  What is the distance (in cm) on a map with a scale of 1:20,000?

10.   The distance along a straight section of road is 1 km.  The road occurs at 700 m elevation.   The length of the road on photo 15BC77991-12 measures 11 cm.  In a different portion of the photo the elevation is 500 m.  What is the scale of the photo at this location.

11.    How many hectares are covered by a standard air photo at a scale of a) 1” = ¼ mile, and b) 1: 60,000