Photo-what, you say?
Photogrammetry is the science of obtaining reliable measurements by interpreting photographs and other methods of remote sensing.
Although the first photogrammetrical devices were invented in the late 19th century, it wasn’t until the 1940’s that there was a revolution in map-making with the advent of aerial photography and photogrammetry.
Previously, cartographers had to walk the landscape they were mapping and carry around a portable drawing board on a tripod with a sighting device!
With photogammetry, cameras were mounted on planes and cartographers had to place together multiple photographs of a landscape, employing the “principles of perspective geometry using horizon lines, vanishing points etc,” This required super human precision so they developed ever more complicated tandem and multi lens cameras.
Modern photogrammetry is an altogether more complex affair thanks to the rise of technology and computer modeling – see what the boffins are up to now.