Aerial Photography – Geography – UGC NET – Notes

Introduction

• Photographing from air is basically known as aerial photography. The word ‘aerial’ derived in early 17th century from Latin word aerius , and Greek word aerios . The term “photography” is derived from two Greek words phos meaning “light” and graphien meaning “writing” means “writing by light”.
• Aerial photography comes under the branch of Remote Sensing. Platforms from which remote sensing observations are made are aircraft and satellites as they are the most widespread and common platforms. Aerial photography is a part of remote sensing and has wide applications in topographical mapping, engineering, environmental science studies and exploration for oil and minerals etc. In the early stages of development, aerial photographs were obtained from balloons and kites but after the invention of aircrafts in 1903 aircrafts are being used widely for aerial photographs.
• The sun provides the source of energy (electromagnetic radiation or EMR) and the photosensitive film acts as a sensor to record the images. Diversifications observed in the images of photographs shows the different amount of energy being reflected from the objects as recorded on the film. Nowdays aerial photography also become digital where values of reflected electromagnetic radiation is recorded in digital numbers.
• An aerial photograph is any photograph taken from an airborne vehicle (aircraft, drones, balloons, satellites, and so forth). The aerial photograph has many uses in military operations; however, for the purpose of this manual, it will be considered primarily as a map supplement or map substitute.

Characteristics of Aerial Photographs

1. Synoptic View: Recording or taking aerial photographs spatially over large area is like birds eye view from the top. These technologies allows discriminating and detecting small scale features and spatial relationships among them.
2. Time freezing ability: They are defined as virtually permanent records of the existing conditions on Earth’s surface at one point of time, and further can be used as past document.
3. Capability to stop action: They provides a stop action view of dynamic state and are used in studying the variable/dynamic phenomena such as flooding, moving wildlife, traffic, oil spills, forests fires, changing dynamics in natural phenomenon etc.
4. Three-dimensional perspective: Aerial photographs provide a stereoscopic view of the Earth’s surface where one can make horizontal and vertical measurements. 
5. Spectral and spatial resolution: Aerial films are susceptible to electromagnetic rays in wavelengths ((0.3 µm to 0.9 µm) beyond spectral sensitivity of the human eye (0.4 µm to 0.7 µm). 
6. Availability: Airborne photographs can be taken on user specific time and make permanent record at a range of scales for any area.