The National Air Photo Library has a variety of photographic scales available, such as 1:3 000 (large scale) of selected areas, and 1:50 000 (small scale).įiducial marks: small registration marks exposed on the edges of a photograph. The area of ground coverage that is seen on the photo is greater than at larger scales. A small scale photo simply means that ground features are at a smaller, less detailed size. 1:50 000) cover large areas in less detail. The area of ground coverage that is seen on the photo is less than at smaller scales. A large scale photo simply means that ground features are at a larger, more detailed size. 1:25 000) cover small areas in greater detail. Two terms that are normally mentioned when discussing scale are: If a 1 km stretch of highway covers 4 cm on an air photo, the scale is calculated as follows:Ī photographic scale of 1 millimetre on the photograph represents 25 metres on the ground would be expressed as follows: 1 unit on the photo equals "x" units on the ground). Scale: the ratio of the distance between two points on a photo to the actual distance between the same two points on the ground (i.e. The focal length is precisely measured when the camera is calibrated. As focal length increases, image distortion decreases. Basic Concepts of Aerial Photographyįilm: most air photo missions are flown using black and white film, however colour, infrared, and false-colour infrared film are sometimes used for special projects.įocal length: the distance from the middle of the camera lens to the focal plane (i.e. The following material will help you understand the fundamentals of aerial photography by explaining these basic technical concepts. Other important concepts used in aerial photography are stereoscopic coverage, fiducial marks, focal length, roll and frame numbers, and flight lines and index maps. There are several things you can look for to determine what makes one photograph different from another of the same area including type of film, scale, and overlap. Normally, air photos are taken vertically from an aircraft using a highly-accurate camera. An aerial photograph, in broad terms, is any photograph taken from the air.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |