Aerial Photography Services
Aerial photography started as far back as the First World War, when it was used to map enemy trenches and detect troop movements. The pilot of an aircraft would look over the side of the machine with a box camera and take pictures over enemy territory.
Things have moved on considerably since then, and modern aerial survey aircraft are equipped with high resolution, stabilised digital cameras which are fully automatic. Aerial photography falls into 2 main categories; vertical and oblique.
Vertical Photography
Vertical cameras, like the Vexcel UCX as used by Infoterra Ltd, are fitted over a camera aperture in the aircraft fuselage. The camera is fitted into a stabilised mount so that the aircraft pitch, roll and drift do not affect the camera during image capture allowing images to be taken over exact points. The camera records the images onto removable hard disk drives for easy retrieval and subsequent processing. The camera is controlled by computer software that is also fed by high accuracy GPS position and attitude information from an IMU (Inertial Measurement Unit). This ensures very accurate location of the images. Images can be taken as single pictures or in overlapping strips that can be later ‘stitched’ together to form a single large resolution image. The resolution of the final image depends upon the sensor resolution in the camera and the height above the ground at which it is flown. The imagery can be overlapped to provide stereo pairs, from which differences in ground elevation can be extracted, and 3 dimensional models produced.
Leica ADS40
Recent developments in aerial cameras, such as the Leica ADS40, have produced systems that give strips of imagery, instead of single frames. This means less processing by reducing the stitching necessary to produce image mosaics. The camera is capable of providing stereo imagery and colour infrared data as well as panchromatic and colour.
Oblique Photography
When a camera is used to take pictures at an angle from the aircraft to the ground, this is known as oblique photography. The image appears more natural to the eye, but is not suitable for mapping type applications. Simple hand held cameras can be used to take small area photos. More sophisticated multi-camera systems are now in common use, such as the MIDAS as used by Infoterra Ltd. The MIDAS system is computer controlled and records images to removable hard disks. It has a semi-stabilised mount and includes a high accuracy GPS and IMU unit, just like the vertical cameras. The images can also be over-lapped to produce stereo pairs, so that 3 dimensional data can be extracted. When combined with
LIDAR data, highly accurate 3D virtual modals can be produced, as used in Infoterra’s
SKAPE data.
Contact us for further information about our Aerial Photography services
