Relief displacement

Height of object, flying height, focal length, principal point, radial dishtace, relif displacement

1. Relief Displacement (Aerial Photogrammetry , Unit 5) Presentation on Presented by Mr . Amol V . Ghogare Assistant Professor, Civil Engineering Dept. SRES, SCOE, Kopargaon .

2. Calculating Object Heights As with calculating scale, there are multiple methods to determine the height of tall objects (e.g. trees or buildings) in aerial photos. In single aerial photos the two primary methods are the relief/radial displacement method and the shadow methods. Relief/Radial Displacement Method The magnitude of the displacement in the image between the top and the bottom of an object is known as its relief displacement . Relief Displacement exists because photos are a perspective projection. It is related to the height of the object and the distance of the object from the principal point. This method can only be used if the object that is being measured is be far enough from the principal point to measure the displacement and the top and bottom of the object are visible in the photo.

3. Relief displacement is scale variation on aerial photographs caused by variations in terrain elevation.

4. Relief displacement Any objects that are higher or lower than the principal point are displaced from its true planimetric ( x,y ) location on a vertical aerial photograph. This displacement is referred to as relief displacement or terrain distortion . The relief displacement is outward from the principal point for objects whose elevations are above the local datum , and toward the principal point for objects whose elevation are below the local datum The direction of relief displacement is radial from the principal point.

5. The lower the elevation of an object, the more it will be displaced toward the principal point. This effect, called relief displacement .

6. Measurement of Object Height From A Single Aerial Photograph Based on Relief Displacement

7. Relief/Radial Displacement Method Use this to determine the height of object

8. Example: The length of a a displaced building is measured at 2.01 mm and the radial distance to the principal point is 56.43 mm. If the the flying height about the surface is 1220 m, what is the height of the building? Sol:-

9. Thank you