4.8.34. Principal line

Try these first

1. 1.

   What does the principal line connect?

   Hint

   Think about what points are relevant in a photograph.

2. 2.

   Define the term 'Nadir Point'.

   Hint

   Where does the camera look down towards?

3. 3.

   What does the principal line refer to in photogrammetry?

   • A reference to ground signals
   • A line connecting the principal point and the nadir point
   • A guideline for capturing images

   Hint

   Look for the two main points related to camera positioning.

4. 4.

   True or False: The nadir point is always the highest point in the photograph.

   • True
   • False

   Hint

   Consider the position of the camera and what point it observes.

5. 5.

   Given the principal point coordinate and nadir point coordinate, explain how the principal line can be plotted and what implications it has on measurement accuracy.

   Hint

   Consider Cartesian coordinates!

6. 6.

   Assume an aerial photograph has a principal line incorrectly determined due to tilt. Discuss the potential spatial analysis errors that could arise.

   Hint

   What other areas might this distortion affect?