The Book of Alternative Data

CHAPTER 13Satellite Imagery and Aerial Photography

13.1. INTRODUCTION

On October 4, 1957, the Soviet Union launched Sputnik I, the first artificial satellite in space. The first image of the earth captured by a satellite was made by NASA's Explorer VI Earth satellite (NASA, 2009) on August 14, 1959 (see Figure 13.1). The picture shows a sunlit area of the Central Pacific Ocean and its cloud cover. The photo was taken when the satellite was about 27,000 km above the surface of the Earth.

Of course, this was not the first time that Earth had been observed from the sky. During the First World War, for example, aerial photography became a significant weapon. While only a few hundred photos may have been taken in the first six months of the war, in 1918 Britain produced just over 5 million aerial photographs (Cable, 2015). And this was not the first example of aerial observation for military purposes. In the American Civil War, Thaddeus Lowe used a hot air balloon to perform aerial reconnaissance for the Union against the Confederate forces.

The most obvious difference between satellite imagery and aerial photography is the difference in altitude at which images are taken. From a much higher altitude, a satellite image will be able to capture a larger area. Furthermore, it can also capture weather patterns more easily and broadly. Satellites also regularly pass over the same spots, so they can potentially provide regular updates, and in effect in recent years this frequency has ...