Take Home Exercises

CE_203

Photogrammetry

1) In an area the terrain elevation varies between 200 m to 500 m above mean sea level. The focal length of the camera is 150 mm and the flying height is 4500 m. calculate the maximum scale, minimum scale, Average scale and datum scale.

2) Calculate the scale of a vertical aerial photograph on which a section line is measured as 150.62 mm. This line was found to be 10.69 cm on a map of the same area at a scale of 1:150000.

3) Three points P, Q and R were chosen on a vertical aerial photograph. On a contoured map their elevation was found to be 1400m, 900 m and 1100 m above mean sea level. If the flying height of the air craft above mean sea level is 3500 m and the focal length of the camera lens is 160 mm, calculate the average scale of the aerial photograph.

4) Two ground points P and Q appear on an aerial photograph as p and q respectively. The photograph was taken from a camera of 220 mm focal length from an altitude of 2800 m. Calculate the distance between points P and Q on the ground. Photo coordinate of point a and b were measured as under:

Point Photo coordinate

x (mm) y (mm)

p +23.8 +16.4

q -13.6 -29.7

5) Image of a tower appears in photograph taken from an elevation of 800 m above the datum. The radial distance of top and bottom of the tower from the principal point is observed as 112.2 and 81.6 mm respectively. The bottom of the tower is at 250 m. Calculate the height of the tower.

6) A ground point that is 230 m above the mean sea level imaged at 34.8 mm from the principal point. Calculate the relief displacement if the flying height is 1600m above the mean sea level.

7) A camera having focal length of 200mm is to be used to take vertical photograph of a terrain having an average elevation of 2000 m. At what height above the datum the air craft should fly to have photograph scale as 1:5000 scales.

8) A straight reach of canal between two stations P and Q that are 618.9 m apart has been imaged as a and b on a photograph with 220 mm focal length.. The elevation of P and Q are 400 m and 600 m respectively above mean sea level. Calculate the flying height if the photo coordinate of point a and b are measured as under:

Point Photo coordinate

x (mm) y (mm)

P +23.8 +16.4

q -13.6 -29.7

9) An area having 40 km in the north south direction and 36 km in east west direction is to be surveyed photogrammetrically. For this aerial photography is to be made with the following basic data. Size of the photograph , 20 cm x 20 cm, Average scale of photograph 1:15000, aeverage elevation of the terrain 450 m, end lap 60 %, side lap 30 %, ground speed of the air craft 220 km /hr, focal length of the camera lens 30 cm. Calculate the flying height of the aircraft, number of photograph in each flight (strip), number of flights (strips ), Total number of photographs, spacing of flight lines, ground distance between exposures, and exposure interval.

10) In a pair of overlapping aerial photograph the mean distance between the two principal points lying on the datum is 6.385 cm. The flying height of the aircraft at the time of the photography was 580 m above the datum. The focal length of the camera is 150 mm. Calculate the difference of parallax for top and bottom of tower of 115 m having base in the datum surface.

11) The mean principal base of a pair of photograph taken from an altitude of 5500 m above mean sea level is 92 mm. The difference between two points is 1.50 mm. If the elevation of the lower point is 480 m above the mean sea level, calculate the elevation of the higher point.

12) The parallax bar reading of two points P and Q having elevations 560 m and 482 m are 14.54 mm and 13.85 mm. The mean principal base of the photograph is 88.4 mm. Parallax bar reading to the third point R is 14.13 mm. Calculate the flying height of the aircraft and elevation of the point R.