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Preserving the Past, Informing the Future | Skip Navigation Links |
Understanding and Interpreting Aerial Photographs
Picture sources: Left: Connecticut State Archives, RG089: 11a, 1934 Connecticut Aerial Survey Photograph 08803.
Right: University of Connecticut, Center for Land Use Education and Research Connecticut 2004 Digital Orthophotos Beta Version.
Interpreting Aerial Photographs
A "casual user of these images is wise to spend a few minutes learning to distinguish a small cloud shadow from a small lake, an air force base from a civilian airport, or a stand of young timber from a grassy hillside. … [U]sers are likely to examine the photographs and USGS topographic maps together, perhaps alternating between the two to connect place names and road numbers with unidentified features in the photographs." From Interpreting Aerial Photographs from the United States Geological Survey, Digital Backyard and the National Aerial Photography Program.
- Interpretation of Aerial Photographs from Dr. Gail Ludwig’s Geography Courses on the Web from the University of Missouri. Describes such things as size, shape, tone, pattern and texture.
- RST : the Remote Sensing Tutorial also called Dr. Nicholas Short’s Remote Sensing Tutorial. From National Aeronautics and Space Administration. You might want to start with the Table of Contents and then go to the overview.
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Washington (State) Dept. of Ecology Shoreline Aerial Photographs The site has a nice drawing to illustrate how to use the layers to find a photo.
What does “geo-referencing” mean?
Geo-referencing is a painstaking process to determine the latitude and longitude of four or five points on a map, aerial photograph or aerial mosaic panel. With that information and the right software, every point on the map or photograph is associated with its own latitude and longitude. Because they are geo-referenced, users with sophisticated software can merge and layer information from different geo-referenced maps and databases to make new maps. The 1934 Connecticut Aerial Photograph Mosaic was created from 239 images that were geo-referenced and combined to make one statewide photograph. See the Project Report.
- Glossary of Cartographic Terms from Perry-Casteñada Library Map Collection.
- GIS Dictionary from University of Edinburgh and Association for Geographic Information.
What is a Quad Map?
The U.S. Geological Survey drew a grid on a map of the United States. Each box on the grid is a quadrangle. Map makers refers to their maps as quadrangles when the area represented on the map is the same as the area within one of the standardized boxes on the USGS map. Quadrangle maps are also called quad maps.
What is an Index Sheet?
Index Sheets show the location of aerial photographs relative to each other and give an indication of what part of the state is shown on the photographs. The Connecticut State Library has aerial surveys from 1934, 1951 and every five years starting with 1965. Each year has a different set of index sheets, and the method for using each set is unique. Some are drawn over U.S. Geological Survey topographic maps. On these index sheets, a box shows the outline of each photograph or a dot shows the center point of each photograph. Other index sheets are a composite, or mosaic, of all the photographs showing how they relate to each other. Refer to the Research Guide to Aerial Photographs at the Connecticut State Library for instructions specific to each survey.
What is a Topographic Map?
U.S. Geological Survey, Frequently Asked Questions: What is a topographic map?
Other Resources
- Connecticut's 1934 Aerial Survey, online
- History of Aerial Photography in Connecticut
- Report on the State Library scanning projects: 1934 Aerial Survey of Connecticut
- Research Guide to Aerial Photographs at the Connecticut State Library
- Using Mosaics and Maps on UConn Web Sites
Prepared 2006 by Jane F. Cullinane, Preservation Office. Revised 2009.