I georeferenced a 1940 black and white aerial photo of part of the coastal area of Santa Cruz Island, California, to the ESRI World Imagery (WGS84) basemap. (The photo source was the UCSB Library FrameFinder archive of historical air photos). The projection is WGS 1984 UTM Zone 11 N. In this "first try" instance, using only a simple first-order polynomial transformation, I created 5 control points (mostly targeting identifiably identical landscape features, like the base of a V-shaped intersection between two cliffs). RMS errors were unfortunately quite high, at 20.396787 forward and 0.036701 inverse.
Keep reading with a 7-day free trial
Subscribe to The Weekly Anthropocene to keep reading this post and get 7 days of free access to the full post archives.