How much detail can a satellite see

These can be used for research purposes and for responses to emergencies. Recently media outlets widely used imagery from the GeoEye-1 satellite to show tsunami devastation in Japan. Sometimes a satellite passes overhead at just the right time to capture a rapid change. The Indian Ocean tsunami on December 26, was one of those times. The QuickBird satellite just happened to pass over Sri Lanka when the wave of water crashed ashore, providing an amazing and scary image. In the same satellite provided images of New Orleans immediately after Hurricane Katrina.

I had an opportunity to closely examine those images at the time, and I remember making a sobering calculation of how much of the city remained submerged. So the detail visible in a satellite image all depends on the mission of each satellite and the scale of its observations. A few non-military satellites can see objects down to about half the size of a car.

Some military satellites can still see even smaller things. But that does not tell us the whole story. For most applications we need to see larger areas, which requires other satellites that observe at a different scale. For each satellite imaging project, we need to choose between seeing small details or seeing a large area. You can't usually have both. Because instead of close-up high resolution images, our polar-orbiting satellites provide much more frequent coverage twice daily over the whole planet in order to understand global weather patterns.

Take a look at the three images below. Side by side you can see the effect of the resolution of each of the satellites. NOAA satellites employ a wide swath to capture a large area in one image. This allows us to see major weather developing over large distances. For a satellite to see your house, it would need to capture imagery at one meter per pixel or higher resolution , such as that from the WorldView-3 satellite. When the devastating wildfires broke out in northern California in early October , satellites captured some of the first images of the affected areas.

Below is a comparison of three satellite images at various resolutions and information on how they each helped first responders on the ground assess the damage and plan for recovery. The VIIRS image demonstrates the large scale and dramatic impact of the fires over a significantly large area. Volcanic plumes also vary in appearance, depending on the type of eruption. Plumes of steam and gas are white. Ash plumes are brown.

Resuspended volcanic ash is also brown. Looking at a satellite image, you see everything between the satellite and the ground clouds, dust, haze, land in a single, flat plane. This means that a white patch might be a cloud, but it could also be snow or a salt flat or sunglint. The combination of context, shape, and texture will help you tell the difference.

For example, shadows cast by clouds or mountains can be easy to mistake for other dark surface features like water, forest, or burned land. Looking at other images of the same area taken at another time can help eliminate confusion. Most of the time, context will help you see the source of the shadow—a cloud or mountain—by comparing the shape of the shadow to other features in the image.

When you get lost, the simplest way to figure out where you are is to find a familiar landmark and orient yourself with respect to it. The same technique applies to satellite images. If you know where north is, you can figure out if that mountain range is running north to south or east to west, or if a city is on the east side of the river or the west.

These details can help you match the features to a map. On the Earth Observatory, most images are oriented so that north is up. All images include a north arrow. Perhaps the most powerful tool for interpreting a satellite image is knowledge of the place. See this linked map that helps differentiate between burned land and non-burned land.

For example, land ownership and land use policy is contrasted in the pair of images below. In Poland, small parcels of privately owned land surround the Niepolomice Forest. The government has managed the forest as a unit since the thirteenth century. While the canopy isn't a solid, unbroken green, the forest is largely intact.

The U. Forest Service manages the forest under a mixed use policy that preserves some forest, while opening other sections to logging. Lighter green areas indicate that logging has occurred on federal, state, or private land. Parcels of private land are much larger in this part of the western United States than in Poland. Land use and conservation policies define the forest area in both Poland top and the U. If you lack knowledge of the area shown, a reference map or atlas can be extremely valuable.

A map gives names to the features you can see in the image, and that gives you the ability to look for additional information. Several online mapping services even provide a satellite view with features labeled. Historic maps, such as those found at the Library of Congress or in the David Rumsey Map Collection , can help you identify changes and may even help you understand why those changes occurred.

Whether you are looking at Earth for science, history, or something else, also consider the Earth Observatory as a key resource. The site hosts a rich, deep archive of more than 12, interpreted satellite images covering a wide range of topics and locations. The archive includes images of natural events as well as more diverse featured images. If the Earth Observatory does not have an image of an area or topic that interests you, please let us know.

Remote Sensing. These images can then go to the negotiating table as countries try to end a war. Or, as in the case of the television show, the images can prove that the official word from a foreign government about some activity on the ground is not true.

The same technology is also used to visualize potential escape routes for criminal activity. One was once reportedly used to observe the underbelly of an orbiting space shuttle for missing ceramic tiles, needed for re-entry.

In the United States, Vandenberg Air Force Base in California has been the primary site for the launch of many surveillance satellites during the Cold War and to the present. Some early satellites had capsules aboard to return film canisters to the Earth. The canisters were snatched in the air by Air Force crews over the Pacific Ocean. Since the special satellites were made by Lockheed Martin, and more recently Boeing has the contract with the National Reconnaissance Office.

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