The effects of that storm are evidenced by the light blue tones in the Potomac River, resulting from a heavy silt load dumped by runoff from the rainfall upstream. The increase in sediment did not affect the Chesapeake Bay to the east. The inner city areas of Baltimore and Washington are accentuated by the blue tones that signify numerous large buildings and a limited number of trees. More than five million people live in this urban region but much of the population dwells in residential areas in which tree-dotted landscapes remain (recent surveys 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, which the U.S. Department of Agriculture operates. Interstate 95 between Washington and Baltimore - the heaviest traveled major road in the East - stands out in contrast to its vegetated edges (look closely for it - it is a thin blue line). Highway 50 past Annapolis, the capital of Maryland, and the high Bay Bridge over the Chesapeake Narrows, visible in the original print, are not seeable on screen.

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

In this image, 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 several of the major roads leading in and out appear as thin dark lines. Two dark patches coincide with the National Airport (just below the center) and Andrews Air Force base (lower right). Farmlands (diminishing as outlying areas are developed into suburbs) make up many of the other darker patterns. We find most of these farms to the east in the Coastal Plains.

The Coastal Plains' precise juncture (at the Fall Line) with the hilly Piedmont (see map on page 6-1 and accompanying text) to the west is obscure but the rolling terrain on the left side of the image infers where the Piedmont begins. A remarkable feature of this image is the three light-toned lines forming part of a square. These lines coincide with the boundary between the District of Columbia and Maryland. Staff at the Jet Propulsion Laboratory (SIR-C's operators) interpreted this tonal phenomenon as expressing strong reflections from building corners that line avenues along the boundaries. But, this writer, who lived in the area for 21 years, is skeptical of the explanation, because there is no unusual concentration of large buildings lining the streets along the boundaries. Along the NE-SW edge many building 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.

Some of these features stand out better when the several radar bands on SIR-C are combined to make this color composite; note that the square boundaries still persist (the red blotches along them are probably not vegetation):

This radar image of part of D.C. was made by an aircraft system operated by JPL as part of its interferometry program to make topographic maps (see page 11-10). The IFSAR system uses two radar images, taken moments apart, that are thus staggered spatially to get a "stereo" effect. In this image, the colors represent variations in elevation, which, although generally less than 30 meters (100 ft) in relief, can still be determined by the radar interferometric method:

The next two images, made by SPOT sensors, present much more detail in the central metropolitan area around the District of Columbia. The false color version at the top (about 24 km [15 mi] 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 mi) on a side, showing the central city and its many federal buildings.

The HRV image falls just within the Capitol Beltway, which rings the Washington area. Several vegetated areas are worth identifying: the wooded area known as Rock Creek Park; Roosevelt Island in the Potomac; the Arlington National Cemetery; and the National Arboretum. The circular Robert F. Kennedy (RFK) stadium is easily identified. The panchromatic SPOT image shows the layout of buildings around the Mall and the downtown business area, as well as homes (many are joined row houses) in the central District. Consult an atlas map to confirm the location of most of the well-known individual edifices. Use major streets such as Independence, Constitution, Pennsylvania, New York, and Massachusetts Avenues, and the Interstate 395 extension, so help locate sites.

The centerpoint in downtown Washington is the Mall that runs from the Lincoln Memorial (4, in picture below) eastward to the U.S. Capitol (3) (Note: The spelling "Capitol" is used to specify the building and immediate surroundings and the hill [Capitol Hill] on which they are located to avoid possible confusion with other federal aspects of the nation's capital.). These two structures, along with the Kennedy Center for the Performing Arts (5), are examples of the graceful white marble edifices that house many of the government offices, monuments, and cultural centers, in what many cite as one of the most beautiful capital cities in the world.

This aerial oblique color photograph, which was taken from the Virginia side of the Potomac affords a "birds-eye" view of this central area.

Visitors to the capital city should recognize many of the landmarks in this picture. On the middle right is the Pentagon, and part of the National Cemetery 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 Pentagon is shown in a high resolution Quickbird image taken in August 2002, about a year after the 9/11 terrorist attacks. See if you can determine which side is under repair at this time.

Because Washington, D.C. is the home base of NASA and it is often hailed as the "Capital of the Free World (or Democracy)", it is a favorite target for imaging by nearly all the Earth-observing satellites currently flying. Although the writer (NMS), from his hands-on experience, has long been partial to Landsat, he now freely admits that Terra (Section 16) is at present the most versatile spacecraft of this genre in the sky. Here is a Terra ASTER 15 m resolution image of Washington that, even though not the equal in detail of those shown below, is, together with imagery from Terra's other sensors, evidence of that versatility:

The image below, displayed in near full screen size, is a merge of a 5 m IRS panchromatic image with a 30 m natural color Landsat subscene. This visually attractive rendition covers much of the Virginia side of the Federal District, including the Arlington National Cemetery and the Pentagon. The Mall layout is well-displayed. The area east of the Capitol is all residential - row houses experiencing a "renaissance" of popularity as lobbyists and others jockey to be near the center of power.

Compare what you can see in this high resolution color aerial photograph below with the scene just above. This should persuade you that space "cameras" are now competitive with those flown on airplanes. For reference, the U.S. Capitol Building and its grounds lie near right center in both scenes (above and below).

The military surveillance satellite KH7 (see page 2-26e) took this 7 meter image of the U.S. Capitol building and grounds in the summer of 1965.

Now to an identification challenge in this next image of downtown Washington, D.C. - a 2-meter (6.6 feet) resolution space photo made by cosmonauts using the Kosmos KVR-1000 camera onboard the Russian Mir space station that was co-registered with a Landsat image.

Use the map below to locate in the IRS and KOSMOS images the following: Washington Monument (note its shadow in the Kosmos image); Jefferson Memorial; Lincoln Memorial; U.S. Capitol Building; Library of Congress; 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; NASA Headquarters, the U.S. Dept. of the Treasury; and Massachusetts and Constitution Avenues.

4-10: There is something (a structure) in this image (related to the Kosmos part) that can give you the approximate time of day when Kosmos was passing over. Can you figure this out and estimate the hour. What important monument is out of the picture? ANSWER

Now, we will take a closer look at the U.S. Capitol and its Reflecting Pool, as seen by SPOT-5's high resolution sensor (note the many changes in this area, compared with the 1965 image above:

Before we leave the U.S. Capitol section of Washington, let's look once again at this IKONOS-2 image showing the left half of the same area as in the above MIR KVR-1000 image. This was first introduced in the Overview to appraise you of the very significant development in applied remote sensing in which high resolution imagery (here, about 2 meters also) has come into the marketplace with the decision by the Russians to "go commercial", followed by the launching of several satellites operated by private companies. In that Overview is also the 1 meter IKONOS panchromatic black and white image of buildings and a bit of the Mall just west of the Capitol Building.

In January, 2002, an even higher resolution (<1 meter) image of the Washington Monument was provided among the first scenes released by the QuickBird satellite launched in later 2001:

To the west of the Washington Monument, the largest new Mall structure in many decades was completed and opened in May 2004. This is the classic World War II Memorial that appears in this Quickbird image as a large uellow-brown (bare soil) patch near right center. During this war more than 490,000 American military were killed (second only to the Civil War in casualties).

You were informed that, in the Landsat scene, the blue area near the top of the Landsat image is the city of Baltimore, Maryland. Since the writer (NMS) lived outside that town for 11 years and has many fond memories of the good life it offered (including winning seasons by the Baltimore Orioles), I would be remiss not to show some images that capture its "flavor". The top one is a standard false color image made by the Landsat-7 ETM+. This shows most of Baltimore's central city, and its western, eastern, and southern suburbs (the northern part is not present). Conspicuous is the large inlet coming off Chesapeake Bay to the east, as rising post-glacial waters invaded the Patapsco Valley.

Second is a JERS-1 image of the downtown, with its wonderful Inner Harbor development. Below that is a color photo looking at the skyline. Unlike Washington, which has a restriction on the height of buildings to keep a balance in proportion, Baltimore, like most big U.S. cities, has an imposing set of tall buildings, as seen in the ground photo that shows much of the Inner Harbor.

The next image was made by the IKONOS satellite. It is among several used in the movie "The Sum of All Fears", adapted from the book by Tom Clancy. In the book, the football field in Denver was the one blown up by a terrorist nuclear bomb. For the movie, the scene was shifted to Baltimore where hero Jack Ryan's wife worked as a medical doctor. In this image, details of the Inner Harbor stand out; the Camden Yards stadium, home of the Baltimore Orioles baseball team, appears near the bottom, along with part of the ("blown-up") stadium used by the Baltimore Ravens football team.

This map, produced by the Maryland Tourist Bureau, shows most of the landmarks and tourist attractions in central Baltimore:

Urban areas are normally warmer by several degrees or more relative to the suburbs and countryside. This is often referred to as the "heat island" effect. This Landsat-2 image of Baltimore shows a much warmer area (lighter tones) in the central city around the Inner Harbor:

At this point, the writer (NMS) has chosen to take a liberty in adding some material to the Baltimore story. That story includes a remarkable renaissance of the city starting in the 1970s. This is largely the result of one person - the dynamic Donald Schaefer, who was mayor for 16 years (later, Governor of Maryland). Mayor Schaefer has a passionate love for his hometown which prompted him to devise a master plan that would attract both industry and suburban citizens who were enticed to return to the central city.

The writer visits Maryland several times a year, mainly to see our son and his family in Bowie, MD. My wife and I have always had an affinity to Baltimore living, the outcome of our 11 years in a western suburb. Now, when journeying to Bowie, I always skip the Beltway around Baltimore, taking instead a direct (and nostalgic) route on the Jones Falls Parkway to the downtown area and then out via the two stadiums that are home to the Baltimore Orioles (baseball) and the Baltimore Ravens (football). On September 2, 2006 I elected to vary the route by turning west just before reaching the downtown stretch. This was "new" exploration, and I got lost. Somehow, the exit street kept changing its name and subtly its direction, so that we veered south. What we saw was amazing in its quality and variety. A renovated midtown with splendid buildings! Then, a neighborhood (Baltimore is famed for its ethnic neighborhood varieties) that had old granite stone cobbles in a street and beautifully restored rowhouses:

We continued in some direction (no Sun for guidance as we drove through the remnants of a hurricane) and eventually came to a boulevard that passed by the landmark Federal Hill - a Civil War fort that guarded the old harbor area along with the better known nearby Fort McHenry (the site of the bombardment in the War of 1812 that inspired Francis Scott Key to write the Star-Spangled Banner).

The view northeast from the Key Highway in the Federal Hill area was awesome to the writer, which included this vista:

The next two photos zero end on parts of the Inner Harbor (HarborPlace):

Try to locate these last two scenes in the IKONOS image above.

The citybred writer has added Baltimore to his "short" list of favorite cities in America: San Francisco, CA; Charleston, SC; Boston, MA; now Baltimore, MD.

Before leaving this segment of the Metropolitan Corridor, lets look at two practical applications. A Landsat subscene that includes both Washington and Baltimore has been processed by a special algorithm to classify ground cover to determine the degree to which the surface acts as impervious (the term refers to ability of water to penetrate into the substrate) to rainfall (this is important in specifying how much water enters the ground and estimating the water that remains to cause possible flooding). Red is highly impermeable, i.e., strongly impervious; blue is moderate and green is low impervious. Reds associate with inner city dominance of buildings and roads; blues are typical of suburbs; and greens generally associate with forests and fields.

The Washington-Baltimore city environs and the "corridor" between these two metropolises that are centered about 60 km (40 miles) apart are experiencing rapid growth - especially the areas in Virginia near the Nation's capital. A visual overview of this growth is evident in this image which utilize Landsat imagery to broadly classify major urban land cover types in 1986. (This is part of a study of urban change, called SLEUTH, conducted by Claire Jantz of the University of Maryland and Scott Goetz of Woods Hole [MA] Oceanographic Institute; it is summarized on this Web Site.)

Compare the patterns of high density metropolitan population in 1986 with this SLEUTH map made from IKONOS images (used to provide more detail) obtained in the year 2000:

The SLEUTH workers have analyzed these change detection images to pick out patterns and trends in population dispersion. Using that information they have generated a forecast map indicating the population distribution in terms of land cover in the year 2030 if no major effort is made to guide and control the expansion. Here is their map in which growth is largely unplanned and follows a "free market" approach:

Finally, here are two Landsat images of Philadelphia, PA region - now grown to about 4 million (if the suburbs and Wilmington, Delaware are included) from the original 30000 people during the Revolutionary War:

The size of the city's environs is misleading, if one goes only by the blue areas. Most of the red areas are actually populated suburbs, which are noted for their preservation of natural and planted trees.

One of the first tasks taken on by the writer (NMS) as he learned the "trade" of remote sensing was to examine digital data for Philadelphia from Landsat-1. On the IDIMS processor at Goddard Space Flight Center, he did a density slice using MSS Band 6. Six levels of grouped DNs were selected: Yellow; Red; Purple; Orange; Green; Blue. This was the result:

Dominantly green, of course, associated with forest cover and blue with water. The denser populated areas in and around Philadelphia in yellows and reds correspond to surfaces with little or limited vegetation. The purples and oranges seem to denote built-up suburbs. Conclusion: as a first approximation, level slicing using Landsat imagery worked well in this case.

Today, Philadelphia is still among the largest cities in the U.S. This photograph was taken of the central city by astronauts onboard the International Space Station.

As one drives along the Schuylkill Expressway, next to the river of that name, the skyline of Philadelphia makes a strong impression:

In the midst of these leviathan buildings sits Independence Hall - Cradle of Democracy.

---

Primary Author: Nicholas M. Short, Sr.