The higher resolution of the Landsat TM and the commercial satellites (e.g., IKONOS) facilitates better recognition of many individual buildings, downtown layouts, shopping centers, industrial complexes, and other landmarks in a city. From these images we could draw a street map for most urban areas, if we enlarge the image to fill the screen. We illustrate this with four more examples: the first is New York City and surroundings, then Miami, the largest city on the Florida peninsula, followed by the great Mardi Gras city of New Orleans, Louisiana, and finally Atlanta, Georgia. They are all similar to Los Angeles and San Diego, being metropolitan areas near sea level.
To start, first look at this SIR-C radar color composite that covers the greater New York-New Jersey-Long Island region, which brings out some of the underlying topography. Note the Long Island Sound and Jamaica Bay:
Now, let's look at another Landsat image that focuses on New York City and the New Jersey cities across the Hudson River (you saw this area earlier in the "exam" at the close of Section 1).
For reference, familiarize yourself with this map of New York City's five boroughs;
All five boroughs of New York, including Staten Island, are contained in the above subscene. Newark, Jersey City, and Paterson are also shown. Look for John F. Kennedy Airport and Central Park in Manhattan. Now, find that Park again in this Landsat-7 subscene in which the 20 meter panchromatic image has been combined with TM Bands 1, 2, and 3.
Now let's get down to Earth by zeroing in on Manhattan from the ground, first with a skyline photo of Midtown Manhattan and then a skyline photo of Lower Manhattan from the west (across the Hudson River) and an aerial oblique photo looking north at the skyscrapers in Lower Manhattan. (A little tidbit: from a distance one notices that there are two clusters of skyscrapers separated by a gap of lower buildings [mini-skyscrapers]. Why? Because of the geology underlying Manhattan Island - the tall skyscrapers are built on two outliers of hard, firm crystalline rock foundations but the land between contains a hundred feet or so of weak sediment unable to sustain the weight of tall buildings.)
You may recall that we introduced the topic of the infamous 9/11 attacks on the World Trade Cemter on page 2 of the Overview. Now it is appropriate to consider this historic event in detail, with emphasis on the role remote sensing has played.
The World Trade Center is actually a group of buildings, the two tallest - 110 stories high - being WTC 1 and 2:
Approximately at 9 AM Tuesday on September 11, 2001 a massive terrorist attack on the United States began with the direct crashing of two highjacked commercial U.S. jetliners onto Towers 1 and 2 of the World Trade Center in lower Manhattan. This diagram presents the timeline for the two crashes:
The first crash was unexpected - hence there is no photo of the actual collision. The second hit was captured even as it was happening since by then newspeople and photographers were on the scene:
The collapse of each building caused a ground surge of dust (mostly fine concrete) and debris, similar to the base surge accompanying some volcanic eruptions. People fled from this rapidly advancing debris and some were engulfed by it (with no short term damage, since the dust was cool; many - firemen, police, and workers - experienced long term pulmonary problems afterwards).
Space Imaging Inc. quickly provided two IKONOS images of the New York scene, one taken before the event and the second within a day after the horrific destruction of these, and several adjacent, buildings. Compare these two views, which illustrate the capability of space imagery to provide an overview of a disaster in an urban center:
On Saturday, September 15, after much of the smoke and dust was cleared by a heavy rain, IKONOS captured this 1-meter resolution image (a bit degraded in this rendition) of the World Trade Center devastation and the avenues filled with rescue and recovery vehicles:
Seen from the ground, the extent of the devastation in the WTC complex produces horrific scenes such as this:
Also, several days later, the AVIRIS hyperspectral sensor, flown on an aircraft (see Section 13 for details on this instrument), was directed over the site. With one of its long wavelength bands as part of a color composite, AVIRIS was able to detect "hot spots" of smoldering flames, as seen in this image:
A thermal sensor mounted on an aircraft captured this map of hot spots on September 16:
Nearly two years later, on September 7, 2003, IKONOS imaged ground zero after the time that the destruction site was declared cleared of recovered bodies and debris.
Parts of the site are being prepared for a major rebuilding and Memorial to 9/11. A large Observation building temporarily straddles part of the open area:
There are those (wags) who think that the WTC attack could have been thwarted. The savior they select is none other than that famous gorilla - "you big Ape" says Ann Darrow - in the scifi classic "King Kong" (in the first  version which puts Kong atop the Empire State Building, not the second [shown here] and third film versions):
Seriously, as we leave this topic, 9/11 brought about a rebirth and rededication in the United States that still pervades its society. This is epitomized by this photograph taken soon after the catastrophe:
But life went on during the early days of 9/11 and by the next year some sense of normalcy had returned. Sports played a large role. This Digital Globe Quickbird 2 m resolution image embraces Yankee Stadium, home of the Bronx Bombers - look with nostalgia as this venerable landmark will be abandoned at the end of the 2008 baseball season as the NY Yankees move to a new stadium:
Before we leave this fabulous city, and to break the thread to its recent tragedy, lets consider the region in terms of the marvels of its night life. Here is a night photograph taken from Space Shuttle (Mission STS-36) that shows the five boroughs, Long Island, and the New Jersey side of the Hudson:
But, let us next return to more halcyon days before the Terrorist War, and look at southern Florida. We establish a framework for the Miami metropolis by looking at this large Landsat mosaic (the subject of mosaics is treated in Section 7) constructed from several individual TM scenes, each rendered in quasi-natural color.
This mosaic extends from the Florida Keys at the bottom to the Orlando area in the center of state at the top. To the east is Cape Canaveral, site of all manned and many unmanned NASA space launches. Having set up your bearings, look for the following features in an atlas: the Tampa-St. Petersburg area around Tampa Bay; Fort Myers; Sanibel Island; Lake Okeechobee; the Everglades; Alligator Alley; Fort Lauderdale; the greater Miami region. The famed Everglades (examined in detail on page 3-8) is essentially a wide river of sluggish drainage, flowing over sink depressions through a vast expanse of open water and land covered by sawgrass and hammocks - "tree islands", irregular, often elongated patches of hardwoods. The Everglades, a subtropical environment, is being ecologically threatened as building and drainage to convert to farmlands has seriously disturbed its natural state. Along the southern coast are mangrove swamps and marshes. An extensive farm region has been cultivated in reclaimed land between Lake Okeechobee and the northern edge of the present Everglades. The widely dispersed lake country in central Florida develops from sinkholes and other internal drainage features in the limestone bedrock.
4-6: Find each of the above features in the mosaic, drawing on an atlas as your guide. Where are the Florida Keys? ANSWER
Next, we view a false-color Landsat TM subscene that covers the Miami area and much of the Florida Gold Coast, from West Palm Beach to Fort Lauderdale.
The city and its suburbs generally hug the coastline, being prevented from spreading inland by the eastern edge of the Everglades. The elongated red features that seem to follow curvilinear tracks are hammocks, whose distribution follows water flow patterns. The linear red features are sloughs dredged by engineers to better control flow. The offshore bar that makes up Miami Beach is conspicuous. The slanted linear feature passing through Miami is the Miami Canal that parallels Route 27. Reclaimed swamplands to the north are converted to large farm tracts.
Like most large American cities today, Miami's downtown has an impressive collection of tall buildings:
4-7: Along the coast, locate Coral Gables, Key Biscayne, Miami Beach, Hollywood. Is Fort Lauderdale in the scene? ANSWER
Like some other urban areas in this Section, Miami has been imaged at high resolution, here by IKONOS.
Jacksonville, Orlando, and Tampa-St.Petersburg are the other major population centers in Florida (now holding some 18 million people). Here is a space view of Tampa:
Probably the most visited area in Florida is in and around Orlando. Go east and one gets to the Kennedy Space Center. Go about 20 miles to the west and, 'lo and behold', there is DisneyWorld. These next three pictures tell the story (see their captions):
One of the fastest growing cities in the eastern U.S. in last 30 years is Atlanta, Georgia. Here is a Landsat-5 subscene taken on June 8, 1999.
This next image was made by an airborne multispectral scanner; rather surprising is the low number of high rise buildings in the downtown area. Most growth has led to a great expansion of suburban areas.
Obviously, even more information about an urban center will result from higher resolution imagery. This next subscene shows part of central Atlanta, Georgia, as imaged by the Kosmo's 2-meter KVR-1000 film camera, which flew on the Russian MIR Space Station. This space photo has many of the qualities and details of aerial photos. Features of interest include the Atlanta-Fulton Co. Stadium, until 1997 home of the Braves baseball team, and the convoluted intersection of Interstates 20 (east-west) and 75-85 (north-south).
Now, this sports complex has expanded, as shown in this recent photo with the downtown in the background:
You should be able to match this photo to the Kosmos scene above.
Using Landsat data over the last 26 years, these subimages (reworked as classifications) really reveal the magnitude of urban growth in the Atlanta region:
Turning to New Orleans (treated in detail on page 14-10a), let's set the city into context with its surroundings by looking at two images. The image below is a full Landsat MSS image, cropped to remove the parallelogram effect, in which the city appears in the upper left between Lake Ponchartrain and meanders of the Mississippi River. This January 1973 scene is dominated by the "birds-foot" distributaries and bayous of the Mississippi Delta. They are set off by the subdued false-color reds of the swampy vegetation in moderate winter dormancy, and by the pronounced chalky blue of sediments from the river, as it empties at the currently-active distributary.
Zeroing in on the city itself, this Landsat-7 natural color subscene shows the entire city - siturated mostly on the east side of the Mississippi - and parts of Lake Ponchartrain (note the causeway bridge that was built from New Orleans north from the south edge of the lake).
Running through the city is part of the Gulf Intracoastal Waterway, a continuous 1725 km (1072 mi) long water route from Carrabelle, Florida to Brownsville, Texas. It also connects with the Mississippi River to provide a protected canal-like passageway for pleasure boats and freight barges. Where it doesn't use the open Gulf of Mexico, the waterway is cut inland from the shore to an average depth of 3.7 m (12 ft) and width of 38 m (125 ft). This waterway also merges in the scene with the Inner Harbor Navigation Canal that joins Lake Pontchartrain to the Mississippi River. Note the wharfs along it. Interstate 10 runs eastward here passing through the Gentilly section of New Orleans. Highway 46 follows the river through the suburb of Chalmette. To its north is a large swampy area, or bayou, in St. Bernard Parish. Much of this area is heavily vegetated, but open water (blackish) takes up most of the interior. The New Orleans Lakefront Airport juts into Lake Pontchartrain. Green areas to its southwest are Pontchartrain Park and the University of New Orleans campus.
The Landsat subscene covers a part of the eastern half of the Crescent City, starting with just a bit of the world-famous French Quarter, at the bottom-left corner of the image (Bourbon Street near the Cathedral of St. Louis just enters there). The French Quarter extends from the docks along the Mississippi River, which has powder blue color, resulting from its high silt content that imparts increased reflectance in TM Band 2. Many of the city streets form true square blocks. Some of the larger buildings in this scene are resolvable at the TM's 30 m. resolution. The reds in the city proper are signs of the luxuriant vegetation that is profuse throughout this lovely city. The large body of water, at the top, is the south shore of Lake Pontchartrain, a 57 km (35 mi) wide (1619 sq. km; 625 sq. mi) inland, brackish (mildly salty) lake that connects by an eastward channel to Lake Borgne, which is a saltwater body joined by the Mississippi Sound to the Gulf of Mexico.
Below is a night view of central New Orleans - this city really comes to life after dark, when the humid heat cools and the activities that make this a Fun City commence. Still, New Orleans is a major port and center for the oil industry. The third image shows the downtown skyline.
The next image is a still closer look, consisting of a multiband (with RGB color assignments) SIR-C radar image, taken from the Space Shuttle on October 2, 1994. Compare this with the Landsat-7 image, noting similarities and differences.
Now look at another view of central New Orleans, lying mainly to the southwest of the Landsat subscene. This subscene, about 9 km (6 mi) on a side, shows the city at 10 meters resolution, as imaged by the multispectral scanner on JERS-1, a Japanese satellite launched in 1992. Note the radial pattern of the streets that act like spokes against 000the crescent bend of the Mississippi River. The large white round feature is the Superdome, site of several football Superbowls. Tall buildings downtown are just to its right. The dark patch nearby is astride the Vieux Carre or French Quarter.
4-8: Locate the SIR-C, Landsat 5, and JERS-1 images in the above Landsat-7 MSS natural color subscene. ANSWER
Below is a nightime ground photo of Bourbon Street within the French Quarter (see map shown):
Part of the French Quarter, and another New Orleans landmark, is Jackson Square (named after General [President] Andrew Jackson, the hero of the Battle of New Orleans between the British and the U.S. in the War of 1812); it took place a few weeks after hostilities in the eastern U.S. had ceased by armistice but word of this hadn't reached those in Louisiana.
The French Quarter, in the opinion of most who know 'haute cuisine', has the largest number of fine restaurants in a small space anywhere in the U.S., and rivals Paris for the quality and variety of eating places. Check out the most famous at this Restaurants website.
A tradition after a night touring French Quarter restaurants and bars is to end the evening at the Cafe du Monde (off Jackson Square) for coffee and beignets. The writer (NMS) has done this 3 times; it remains his fondest memory of New Orleans.
The next big city west of New Orleans, and the country's fourth largest, is Houston. Let's look at this city using a variety of space imagery.
The urban area is the home of most of the astronauts, who are headquartered at the Johnson Space Center, Clear Lake. For decades now, almost whenever an astronaut was in a space craft orbiting Earth, he/she would look out as the crew passed over the Houston metropolitan area - and do what any real tourist does - TAKE A PHOTO. Here is a typical picture:
Houston is in the pinewoods of East Texas. In fact, it was carved out of cleared woodlands. Even in the metropolitan area, trees abound in every neighborhood. A sense of the "greenness" of the region is given by this quasi-true color Landsat-7 ETM+ image:
The greater Houston area is home to more than 5 million people. The extent of the metropolitan area stands out in this astronaut photo taken at night:
A better look at Houston and its environs is provided by MODIS (on Terra):
Here is a false color rendition made by the IRS satellite; at the higher resolution, the shadows of downtown buildings are visible:
Now look at this SIR-C X-Band radar image that extends from central Houston to the Gulf Coast at Galveston Island.
The photo below was taken by an astronaut aboard the International Space Station. The camera used is capable of much better resolution than has been acquired in most previous manned missions from space (see Section 12). The views of downtown Houston shows a part of the freeway system built through and around this city. Both Houston and Dallas-Fort Worth (below) have more major urban area road networks than most other American cities, owing to the foresight of transportation planners in recognizing that future growth requires such roadways even at the expense of replacing (removing) homes, etc. to provide the necessary right-of-ways.
Staying in Texas: One of the prime uses of space imagery is that aspect of change detection which examines an urban scene after intervals of years or even decades. This is an invaluable aid to regional planners and even to the Bureau of the Census, which has learned how to use these observations in estimating population changes (helpful to the U.S. Congress in re-allocating federal funds). The next two images are of the Dallas-Fort Worth, TX area (see also page 4-5), in 1974 and 1989.
Both of these cities are now major urban centers - a conclusion one would draw from these views of their downtown skylines:
We will leave it as an exercise for you to evaluate the changes in the 15 years since the 1974 subscene. Are there any new lakes (reservoirs)?
Throughout the Tutorial, but mostly in this Section, we have a number of scenes of Texas. We have covered all Texas' major cities except San Antonio. To avoid possible negativity from its citizens, we show this Landsat image of the city built around the Alamo. Here:
The writer (NMS) would be remiss if he did not feature his home town in this Section. So, below is a Landsat 4 subscene showing St. Louis - the pride of eastern Missouri - the town where, just to its north, the Missouri and Mississippi Rivers meet.
A bit more detail is evident in this Google Earth-Quickbird image:
This is a photo of the St.Louis downtown area, including the stadium that Mark McGwire has made famous and the Gateway Arch, a monument symbolic of the opening of the American West to pioneer settlement:
The downtown section shown in the oblique view is rendered vertically in this March 2002 Quickbird (0.66 m; 2 ft) image:
Four landmarks are singled out: the Gateway Arch; Busch Stadium (St. Louis Cardinals); the TWA Convention Center, and (second from left) the Eads Bridge, first one built across the Mississippi River, considered an engineering marvel in the 1800s (but now closed to auto traffic, but kept intact for its historical significance).
And, for a different perspective, look at this SIR-C radar (from the Shuttle) composite (see Section 8) of the central city, with East St. Louis on the Illinois side (bottom).
Let's close this page with a quick look at our westernmost big city. This next image, made by the Landsat 7 ETM+, was added on December 7, 2001, the 60th anniversary of the Pearl Harbor attack. This is the southern part of the island of Oahu (see page 17-3 for image of Hawaiian Islands).
In the above image, the location of Pearl Harbor relative to the main section of Honolulu is evident. In the next image, taken by International Space Station astronauts, shows that section in more detail (higher resolution). It also better reveals the nature of Diamond Head - it is a small volcano (now extinct) with a wide central crater.
Now, let's head back to the eastern U.S.