Although there have been many lengthy and detailed surveys of many areas of the world, there are still all kinds of reasons that mapmakers would require aerial photos. For example, many roads are surveyed via aerial photography and assessment, and any areas in which habitation is limited will also usually receive their surveys via aerial processes too.
How do aerial photos become accurate maps? It requires existing data of other types and something known as GIS technology. This is something which is frequently used by the USGS (United States Geological Survey) and translates to “geographic information system”. What GIS technology can do is take complex collections of data and apply all kinds of analysis and calculations to create the sort of imagery requested.
For example, following the tragic end of the Space Shuttle Columbia mission in February of 2003, GIS mapping used aerial photos, data from flight recorders, existing topographic maps, weather and wind details, and other information to generate a highly accurate map of the locations for the vast majority of debris from the disaster.
The best modern mapping software will be able to incorporate GIS functionality and also use “layers” of imagery and data to create maps. For instance, a good program might be able to take aerial photos of a vast region, “mosaic” them (piece them together so that they line up accurately), and then reveal topographic details such as altitudes or elevations as non-photographic details in the image. This is something frequently done by modern builders and developers, engineers, and even town and city governments for use in planning projects or understanding chronic issues such as flooding and run-off.
Accurate aerial photos are part of a larger “tool kit” used in modern mapmaking programs and activities, and they are an important component for accuracy and detail.