Aerial Photography is the art of taking photograph of the earth surface from a camera mounted on aircraft. If the camera used is a digital camera, then it is called Digital Aerial Photography . Digital Aerial Photography was developed 4-5 yrs ago. In 1858 Persian photographer and balloonist Felix Nadar took the first Aerial Photograph from a air balloon. At that time there was no concept of Digital Aerial Photography. Simple camera with trigger mechanisms were used for taking photographs. In digital cameras datas are stored in digital format and can be accessed immediately after taking photograph.
Digital Cameras used for Digital Aerial Photography :
The design of digital cameras follow two approaches :
• Linear array scanners which capture the data by scanning the entire topography using linear arrays while the aerial platform sways over the terrain. It constitutes of three sensors- forward facing, vertically facing and backward facing sensors. Overlapping images acquired by the three sensors can help to find the altitude of different features.
• Area array scanners uses one or more area array scanners to scan the terrain. Here the images are sewed jointly to form a grater image which can be refined using digital photogrammetric software.
The main characteristics of digital cameras used for Digital Aerial Photography are:
• Multi-spectral images can be produced some of which exhibit wavelengths from blue to near infrared.
• Geometrically correct
• Panchromatic images having a range of 12 bit and pixel sizes less than 5 cm.
• Large amount of data is stored in both original storage device and backup
Use of Digital Aerial Photography :
• Large scale photography is mainly done with digital photographs
• Used for land-use mapping.
• For mapping any particular project
• Analyzing environmental conditions
• Tourism purposes
• Land cover and change detection
• Geologic mapping
Advantages of Digital Aerial Photography :
• Poor light condition is not any obstruction for Digital Aerial Photography because the degraded film can be eliminated and the dynamic range used in Digital Aerial Photography will help in proper data acquisition.
• Geometrical correctness of the photograph is a great advantage.
• The images can be refined and processed as soon as the aircraft touches the land surface thereby making a relatively quick analysis of the feature whose photograph is taken.
• High level of redundancy will lead to a new ensight to photogrammetic production.
• Redundancy will help to acquire near orthophotos depending on the area on every imagery surrounding the principal point. The relief displacement will be lowest around this point.
• Since the Digital Aerial Photography is suitable for large scale and high spatial resolution, the photos are commercially valuable.
Disadvantages of Digital Aerial Photography:
• Digital Aerial Photography is an expensive process mainly because of the high cost of digital cameras .
• Long term storage of digital data is still a concern for Digital Aerial Photography .
Digital Aerial Photography will be improved much in near future and will definitely become an important source of mapping. A new range of digital cameras is a result of invention of new technologies which are used for Digital Aerial Photography .
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