The higher resolution of the Landsat TM 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 two more examples: the first is from Miami, the largest city on the Florida peninsula and the second is the great Mardi Gras city of New Orleans, Louisiana. They are similar to Los Angeles and San Diego, being metropolitan areas near sea level.

To start, we establish a framework for the Miami metropolis by looking at our first Landsat mosaic (others are 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 our bearings, we suggest looking for the following features 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 is essentially a wide river of sluggish drainage, flowing over sink depressions through a vast expanse of sawgrass and hammocks ("tree islands", seen here as elongated red patches) of hardwoods. 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 of large farm tracts.

4-7: Along the coast, locate Coral Gables, Key Biscayne, Miami Beach, Hollywood. Is Fort Lauderdale in the scene? ANSWER

Turning to New Orleans, let' s set the city into context with its surroundings by looking at two images. The top image is a full Landsat MSS image, in which the city appears in the upper left between Lake Ponchatrain 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. The bottom image is a closer look, consisting of a multi-band (with RGB color assignments) SIR-C radar image, taken from the Space Shuttle on October 2, 1994. Compare the two, noting similarities and differences.

Next look at the TM false-color composite that is a subset from the Landsat 5 scene obtained on March 24, 1985.

Remember that the resolution is 30 m (98 ft). The 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 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. 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.

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 the 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 Landsat MSS subscene. ANSWER

Obviously, even more information about an urban center will result from higher resolution. 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 complex intersection of Interstates 20 (east-west) and 75-85 (north-south).

Collaborators: Code 935 NASA GSFC, GST, USAF Academy
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