FIGURE 8.6 A PHOTOGRAPH USED TO PROVIDE TECHNICAL INFORMATION
Images of the same scene at different times can provide technical information about changes in a physical environment. On the left is a photo of Northwestern Glacier, in Alaska, in 1940; on the right is the same scene in 2005.
Source: National Aeronautics and Space Administration, 2013: http://climate.nasa.gov/state_of_flux#Icemelt_Alaska14.jpg.