Aerial Camera Data

Aerial Cameras

Aerial cameras are highly specialised instruments developed to enable accurate and consistent imagery of the earth to be obtained from an aircraft. They are referred to as "passive sensors" in that they detect and capture the natural light reflected from objects.

Over the years a number of different styles and camera formats have been used but the basics of geometry still needed to be adhered to when utilized for ground measurement and mapping.

Early film cameras were hand-held surveillance instruments used by various armies to obtain pictures of the enemy. These rapidly developed into high altitude "fixed to the aircraft" types that held rolls of film enabling many frames of photography to be exposed in single sorties. These frames overlapped each other by 60 per cent which enabled three dimensional models to be created of the earth's surface. These resulting stereo images were the main source of information for mapping and in particular, ground height depiction for many years.

Later developments in camera and film technology enabled infrared film to be used for specific imagery capture, but it was the advent of digital technology that enabled capture of not only the visible light spectrum but also radiation at either end of the visible light range.

Zeiss RMK film camera

Digital sensors are used in many platforms including satellite, manned aircraft, unmanned aircraft, land-based vehicles and in static placements. Digital cameras have a further advantage in that their imagery pixels can be used to create point cloud elevation data sets.

Digital cameras are similar to film cameras in that they come in a wide variety of formats and styles and each individual unit has to be specifically calibrated to enable accurate measurements of the ground to be obtained.

Calibration Data

If using aerial photography/imagery for any purpose beyond simple viewing, e.g. accurate measurement, it is vital to know the camera/sensor calibration data associated with a particular image. This enables the processes used for correcting the imagery to allow for lens distortion and alignment errors that could produce significant accuracy issues in the final measurements.

Over the years of aerial photography in Tasmania, many different cameras have been utilized and every camera has its own particular orientation and lens distortion errors that need to be taken into calculations. The lens calibration data for the cameras the government has used, is available here as a series of pdfs which contain the calibration data and orientation parameters. These are listed first by the eras in which they were used and then by the particular camera and lens system.