Fugro owns and operates its own survey aircraft which are fitted with the latest technology Digital Mapping Camera's. If you are looking for a service, we can offer aerial photography as a standalone service or as part of a comprehensive mapping project.
Photogrammetry and Vector Mapping
Photogrammetry is the process of producing maps from aerial photography. Aerial photography has inherent distortions due to the rotation of the aircraft and the relief of the terrain. It is the science and mathematics of photogrammetry and survey that seeks to eliminate these distortions and produce an accurate positional measurement of the terrain and features within the photography.
Stereo Aerial Photography
Aerial photography is obtained as a series of overlapping pairs. This overlap allows the images to be viewed in stereo. The survey targets are visible in the photography at key locations throughout the block of photography.
The aerotriangulation process measures the survey locations and other identical points on successive pairs of stereo images. Combining the stereo measurements, ground survey information, and camera data, the photogrammetrist is able to create a block or bundle adjustment across the entire block of photography. The results of aerotriangulation are real world coordinates of photo centers and the precise rotational parameters of each exposure. With this mathematical solution, measurements can be made from the stereo images that are correctly positioned in three-dimensional real world coordinates.
Digital orthophotography is a photogrammetric service that applies the mathematics of photogrammetry to remove the distortions that are inherent in aerial photography. The orthorectification process removes the distortion in the imagery caused by the tip and tilt of the digital camera, the relief of the terrain and the central projection perspective.
Aerial Photography Distortions
Because a photograph is a two-dimensional representation of a three-dimensional object, when you look at the center of an aerial photograph, your view is the same as if you were looking straight down from the aircraft. But as you look toward the edges of the photograph, you are viewing the ground from an oblique angle, no longer straight down. Regardless of where you look at the photo, your view passes through a common point. This is a central perspective projection.
The very center of the aerial photograph is scale correct. Points on the photo that represent a ground elevation higher than the elevation at the center of the photograph are displaced away from the center. Lower elevations are displaced toward the center. In order to create a scale correct aerial image that can be accurately measured, your view needs to be straight down over every point in the photograph.
The orthorectification process takes into account many variables including camera calibration data, the position of the camera at the time of the exposure, the rotational parameters of the camera at the time of the exposure, and the terrain relief. Applying photogrammetric mathematics, each pixel in the image is repositioned to its correct geographical location and covers a specific distance on the ground.