This research guide was created by Thelma Thompson, Government Information and Map Librarian (now retired), and is currently maintained by other librarians at UNH.
This is a guide to aerial photographs (photographs taken from a plane) and satellite imagery. Air photos generally use light in the visible spectrum while satellite images capture various wave lengths of light depending on the specific satellite instrumentation. With multi-spectrum satellite imagery you need specific software to display and manipulate the images.
Many air photos can be viewed as JPG or TIFF images with the same products as used to view other digital photos; some may be in formats for use in a Geographic Information System.
As you might expect, air photos have been around longer than satellite images. We have chosen to separate recent from older air photos since in many cases they may be used differently or accessed differently. Hybrids that have a satellite image as a base map with labelled features and other characteristics of conventional maps are not included in this guide.
Air photos and satellite imagery are often best searched for using a base map to identify your area of interest. Geographic indexing of each separate image allows the list of results to display any photos or images that fall within that area of interest. Depending on the web site, you can usually either enter geographic terms, such as a town name, or locate an area of interest by zooming in or drawing a box.
Remote-sensing imagery: A broad term that includes data collected by either satellites or aircraft and may use a wide variety of wave lengths of emitted or reflected radiation.
Aerial Photograph: A photograph of the earth's surface from a platform not in orbit (generally an airplane). It does not contain any identifying information such as names of towns or natural features.
Photo map: An aerial photo used as a base for a map that does contain identifying information and typically title and other publication information.
Satellite image: A display of data collected via satellite without identifying information such as names of towns or natural features.
Satellite map: A satellite image to which identifying information and publication information has been added.
This guide deals with air photos and satellite images. Photo maps and satellite maps will be covered in information about maps in general.
Time series: Comparable data collected at intervals of time that enables analysis of changes.
Portion of an aerial photograph from UNH's Brown Co. collection
Portions of Landsat images from UNH EOS-EarthData - showing Great Bay
Real-time or near real-time images reveal current conditions, whether buildings and roads or views of unfolding natural hazard events.
They form useful "base maps" for displaying a variety of other information.
When used with historic maps and air photos or older satellite imagery, they can help in documenting changes.
