Module 3 : Photogrammetry
  Lecture 19 : Geometry of tilted photographs
Relief displacement on a Tilted photo
Figure 2: Relief displacement on a tilted photo
  • Figure 2 shows the relief displacement on a tilted photograph. It should be noted that:
  1. On a tilted photo relief displacement (a'a) are radial from nadir point (n).
  2. The amount of relief displacement depends upon: (i) Flying height (ii) distance from nadir point to image (iii) elevation of ground point (iv) position of point with respect to principal line and to the axis of the tilt.
  3. Compared with an equivalent relief displacement on vertical photo, the RD on a tilted photo will be
    • less on the half of the photograph upward from the axis of the tilt,
    • identical for points lying on the axis of the tilt and
    • greater on downward half of the photo.
  4. Image displacement due to the tilt (explained later) tends to compensate relief displacement on the upward half and will be added to RD on the downward half.
  5. Because tilts in near-vertical photos rarely > 3o, therefore the value of RD is given with sufficient accuracy with following equation. However, the radial distance should be measured from the nadir point rather than from the principal point