Aerial Photography

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Aerial photograph y is the art of taking photograph of any feature, landscapes or phenomenon on the earth surface for the purpose of building maps with the help of a camera which may be mounted on any aerial platform or held in hand.

History of Aerial Photography:

In 1858 Persian photographer and balloonist Felix Nadar took the first Aerial Photograph from a air balloon. The airplane was used first by Wilbur Wright for Aerial Photography in 1909. Aerial Photography became popular among military and was used during the first world war in 1918. In 1934, the American School of Photogrammetry was founded to study Aerial Photography . NASA launched its first Landsat Satellite in 1972.

 

Characteristics of Aerial Photography:

Principal point is the point where the perpendicular intersects the object. Nadir is the point which lies vertically below the centre of the lens at the time of exposure. Isocentre is the pont which lies in between the principle point and vertical point. Fiducial Marks are found at the corners and midway between the corners of Aerial Photograph .

Types of Aerial Photography:

• Vertical Aerial Photography : When the lens of the camera remains vertical with the object whose photo is taken i.e. the angle formed with the object is 90°, then it is called vertical Aerial Photography .
• Oblique Aerial Photography : When the lens of the camera is not vertical with the object and the photograph s taken at an angled perspective it is called Oblique Aerial Photography . It can be dived into low and high oblique depending on the angle.

Distortions in Aerial Photography occurs due to change in the location of the photo which alters the basic nature of the photo. The main types of distortions in Aerial Photography are :

Film and Print Shrinkage Atmospheric refraction of light rays Image motion Lens Distortions

Displacement in Aerial Photography is caused by change in the altitude from where the photograph is taken. The main types of displacement in Aerial Photography include :

• Curvature of the Earth
• Tilt
• Topography and relief

Types of film used in Aerial Photography :

• Panchromatic which produces black and white images.
• Infrared which is sensitive to infrared rays along with black and white.
• Color film is the same which is used in hand-held camera.
• Camouflage detection which records vegetation in reddish tone. Blue or purple tone are also found in this type of film.

 

Use of Aerial Photography:

 

• cartography
• land-use planning and mapping
• geologic mapping
• environmental mapping
• archeology
• commercial mapping

Advantages of Aerial Photography :

• Aerial Photograph y provides an ever lasting memorializing of data and the current view of the earth surface.
• The spectral sensitivity is more encompassing than human eyes and the photo is obtained quickly.
• The spatial resolution of Aerial Photography is better than any other imagery.

Disadvantages of Aerial Photography :

• Images cannot be identified without taking stereoscopic views and overlapping photographs.
• Interpretation is difficult in poor light condition.
• To interpret a map proper training is essential.
• Only marginal data is found.

 

But it can be said that despite of some shortcomings, Aerial Photography is considered as an important tool for map making even today.