Aerial photography is the practice of taking pictures of the earth’s surface from overhead. It is a form of remote sensing that is distinguished from satellite imagery in that the pictures are taken from nearer surface altitudes than those maintained by satellites that orbit the earth in space. The first aerial photographs were taken from hot-air balloons in the mid-1800s. More recently, aerial photographs have often been taken from fixed-wing aircraft and today can even be taken from unmanned aerial vehicles (also knowns as drones).
This guide provides a listing of resources that serve as a starting point for researchers who are interested in using historic aerial photography in their work. ‘Historic’ here refers to negative, print and digitized aerial photographs that were not originally produced as digital orthorectified georeferenced data products (these are covered in the Remote Sensing guide). The practice of georeferencing ties objects that are represented on a photograph to a reference coordinate system so that they can be imported into a geographic information system (GIS) and overlaid with other geospatial data. The practice of orthorectification corrects distortions that exist in photographs that are the result of non-orthogonal (i.e. not taken from directly overhead) view angles and complex terrain.
Historic aerial photographs are perhaps most useful in combination with contemporary imagery to examine change over time. Examination can be either qualitative or quantitative. The quantification of change typically requires that aerial photographs from each time-period of interest first go through the georeferencing and orthorectification processes.
Penn State University Libraries collections encompass ONLY Pennsylvania. Please consult our guide on how to access historic aerial photographs from US government websites. Each state is different and varies in how accessible their data is. Your best bet is to contact a large research library in the state you are interested in and ask them. They will be the most knowledgeable about the data in their state.