Landsat Image Interpretation Examples

Since we have been discussing Landsat imagery (and the French SPOT satellite, which we referred to, but haven't seen any imagery from as of yet) this little section of the  NASA remote sensing tutorial (from  Section 4: Urban and Land Use Applications) seemed like a good place to have you start, since I am not in class today because I am attending a meeting in Washington.  

After you have read through this section, I would like you to go through the NASA remote sensing tutorial Section 6: Flight across the United States.  A link is provided below after the discussion of the Capitol.  As you review these images, and try to identify the different features which are discussed, keep in mind the tutorial section which described how these false color images are made by compositing MSS or TM bands.  When you have finished this material, I would like you to send me an e-mail indicating 5 different applications (commercial or otherwise) for Landsat satellite imagery.  If you have any trouble with this, you can browse through the Landsat and SPOT Homepages (which you can connect to from the EVSC494 Links page).   It is safe to assume that since I know you will have read this information, a test question regarding the interpretation of these types of imagery will appear on the exam.

The U.S. Capital: Washington, D.C.

We now swing up the eastern seaboard to focus on the southern part of the great metropolitan corridor that runs from Boston through New York and Philadelphia past Baltimore and Washington, D.C. The latter two cities are shown below in a subscene (about 113 km [70 miles] across) taken from the October 11, 1972 pass of Landsat-1 on a remarkable viewing day in which the air was crystal-clear after passage of a major storm.

The effects of that storm are evidenced by the light blue tones in the Potomac River, resulting from a heavy silt load introduced by runoff from the rainfall upstream. The Chesapeake Bay to the east is, of course, unaffected by this increase in sediment. The inner city areas of both Baltimore and Washington are easily singled out by the blue tones that bespeak of numerous larger buildings and a limited number of trees. More than 5 million people live in this urban region but much of the population dwells in residential areas in which tree-dotted landscapes remain (recent surveys have identified the Washington area, in particular, as the most heavily forested urban locale in the eastern U.S.). A large blotch of deep red (abundance of trees) in the northeast part of the Washington suburbs represents the largely undeveloped tract of land comprising the Beltsville Agricultural Experiment Station operated by the U.S. Department of Agriculture. Interstate 95 - the heaviest traveled major road in the East - between Washington and Baltimore stands out in contrast to its vegetated edges. Highway 50 past Annapolis, the capital of Maryland, can also be seen and, if you look closely, the high Bay Bridge over the Chesapeake narrows is just visible.

We will use a SIR-C L-band radar image obtained on April 18, 1994 from the Space Shuttle to take a closer look at the metropolitan area surrounding the U.S. capital.

To orient you: north is to the upper right. No distinct tonal patterns marking the more densely populated and built-up sections of the area are evident but many of the major roads leading in and out appear as thin dark lines. Two dark patches coincide with the National Airport and Andrews Air Force base (lower right). Farmlands (diminishing as outlying areas develop) make up many of the other darker patterns. Most of these are found to the east in the Coastal Plains. Its precise juncture (at the Fall Line) with the hilly Piedmont (see map on page 6-1 and following text) to the west is obscure but the Piedmont itself can be inferred by the suggestion of more rolling terrain on the left side of the image. A remarkable feature of this image is the three light-toned lines forming part of a square. This coincides with the actual boundaries of the District of Columbia and Maryland to the outside. Staff at the Jet Propulsion Laboratory (SIR-C's operators) have interpreted this tonal phenomenon as expressing strong reflections from building corners that line avenues along the boundaries. But, this writer (NMS, who lived in the area for 21 years) is skeptical of the explanation because he has not observed any unusual concentration of large buildings exclusive to the streets along the boundaries, (along the NE-SW edge many are residences no different than other homes away from the boundary streets). The line next to the boundary running NW-SE (right side of square) that continues beyond the District is a power line.

Much more detail is presented in the next two SPOT images. The false color version at the top (about 24 km [15 miles] on a side) is made by the HRV multispectral sensor that provides 20 meter resolution. On the bottom is a 10 meter panchromatic image that extends about 13 km (8 miles) on a side, showing the central city and its many federal buildings.

The HRV image just about encompasses the Capitol Beltway which rings the Washington area but does not stand out here. Several vegetated areas are worth identifying: the wooded area known as Rock Creek Park; Roosevelt Island in the Potomac; the Arlington National Cemetary; the National Arboretum. The circular Robert F. Kennedy (RFK) stadium is easily picked out. (Check an atlas to locate these features.)

The centerpoint in this and the next two images is the Mall that runs from the Lincoln Memorial (4) eastward to the U.S. Capitol building (3). These two buildings (see below), along with the Kennedy Center for the Performing Arts (5), are symbolic of the graceful white marble edifices that make up the many government offices, monuments, and cultural centers in what many believe to be one of the most beautiful capital cities in the world.

A "birds-eye" view of this central area is afforded by this aerial oblique color photograph taken from the Virginia side of the Potomac.

Those viewers who have visited the capital city before should recognize many of the landmarks. On the lower right is the Pentagon and part of the National Cemetary is in the foreground. Beyond Roosevelt Island is the Kennedy Center. Nearby are the Lincoln Memorial and, on the Tidal Basin, the Jefferson Memorial. The White House is hidden by trees but the Ellipse (a near-circular drive and parkland) is just to its south. The Washington Monument is too thin to be seen clearly in this photo. But, many government office buildings lining the mall are evident.

The panchromatic SPOT image seen above shows the layout of buildings around the Mall and the downtown business area as well as homes (many are joined row houses) in the District. Again, consult a map to confirm the location of most of the well-known individual edifices. To orient yourself, pick out major streetways such as Independence, Constitution, Pennsylvania, New York, and Massachusetts Avenues, and the Interstate 395 extension.

We offer you an identification challenge in this last image of Washington, D.C. It is constructed from the merge of a Landsat TM subscene rendered in the IHS (Intensity; Hue; Saturation) color system and a 2-meter (6.6 feet) resolution space photo made by cosmonauts using the Kosmos KVR-1000 camera onboard the Russian Mir space station.

Use a map to locate the following: Washington Monument; Jefferson Memorial; U.S. Capitol Building; Union Station; National Air and Space Museum; Hirschorn Gallery; National Gallery of Art; National Museum of Natural History; Smithsonian Administration Building; Federal Bureau of Investigation (FBI); The White House; U.S. Dept. of State; U.S. Dept. of the Treasury. What important monument is out of the picture? Also, don't look for the NASA building if you have an older map- its headquarters has moved and most atlases don't show this new location.

NASA Remote Sensing Tutorial; Section 6: Flight Across the United States

Back to Syllabus