Old satellite images are easy to find through several different programs. Google Earth is the easiest to access and use but several others also offer date- and time-based imagery without requiring a paid subscription. Images are not always available, however, and in many cases, you must settle for an image taken close to the date. Anything predating satellite imagery is obviously not available either.
Reasons for Viewing Old Imagery
Historic satellite imagery is useful for a variety of reasons. The imagery is often used by scientists to view physical changes in the landscape. Studying climate change, deforestation and development are all aided by historic imagery. A scientist can watch changes in glaciers while a biologist in the Amazon can study changes in the landscape as farms replace forests.
Surveyors and planners also benefit from historic imagery. Viewing city grids, power line routes and general features in the landscape is all possible through historic images. Google Maps is a tool used frequently by professionals in the planning and mapping fields.
General interest is another common reason for using imagery. Viewing old home locations, historic buildings and other features in a city or natural landscape is simple with historic imagery. Personal curiosity is not an uncommon reason for looking at old satellite images.
Google Earth Imagery
Google Earth made satellite imagery easily accessible to everyone. The program is now rolled into Google Maps and you can quickly toggle between street maps, street view images, topographical maps and satellite imagery. The default for Google satellite view is the latest imagery taken and stored. You can, however, search for imagery from previous dates.
To find older imagery on Google Maps, simply open the program in a web browser and navigate to the desired location. Either enter the longitude and latitude coordinates or use a common marker like a street address to find the point of interest. Next, look to the bottom left-hand corner on the maps and click the satellite option to bring up the imagery.
Click on View and choose Historical Imagery to view older images of the location. Also, consider changing the time for a different view. The time of day change alters the angle of the sun and can illuminate different aspects of the imagery. The change is effective when you really need to find details in the imagery. Simply click the sun icon and drag the Google Earth timeline slider left or right to alter the angle.
USGS Date Filters
The U.S. Geological Survey focuses largely on measuring snowpack and river flows. They also have a digital program called EarthExplorer. The satellite imagery has excellent detail and custom search options with numerous features and filters. Enter the address or the coordinates to retrieve zoom on the location. Map and satellite views are both available and toggling between the two is easy.
Next, enter a date range for the imagery. Using the date feature, the most relevant map view will return with satellite imagery from that date range if available. If the imagery is not available, expanding the date range is often necessary. After retrieving the imagery, you can take a screenshot or save maps if desired.
The USGS maps are a great way to find old aerial photos free. While they don't have the directions and street view like Google, the ability to view detailed satellite imagery while filtering dates makes it an excellent tool.