It is a combination of a traditional Aerial survey and a Vertical Face Survey. The benefit is that it would also deliver a high quality orthophoto for inspection purposes and a DEM.
- Complete a normal aerial survey over the dam wall
- Use 3rd party Software to Extract an Orthophoto and DEM from this survey
- Import the Ortho & DEM into DH
- Use the Ortho and DEM to mark the toe and the top of the wall and a polygon to mark the boundaries of the survey
- All the images will be taken horizontally. (or if you're really clever set the camera to be 90 deg to the approx slope of the wall)
- Select the flying distance off the wall.
- Because dam walls aren't vertical, it will mean that each new run has to move towards the wall to keep the required offset