Chapter
3    

Julie A. Robinson, Brett McRay, and Kamlesh P. Lulla

Office of Earth Sciences
NASA Johnson Space Center
Houston, Texas USA

Abstract

Rapid land-use change around urban areas has become a sensitive environmental and political issue in the late twentieth century. We quantified growth of North American cities using photographs taken by astronauts from low Earth orbit. The study included a set of six North American cities that have expanded over the last 30 years, including Vancouver (British Columbia), Chicago, San Francisco Bay area, Dallas/Fort Worth, Las Vegas, and Mexico City. We identified baseline photographs of each city from Apollo 9 (1969) or Skylab (1973-1974), and paired them to photographs taken during the Shuttle-Mir Program (1996-1998).

The photographs were digitized, registered to each other, resampled to a uniform per-pixel scale. We used visual photointerpretation to delimit the boundary of built-up area, and manually digitized the boundary to the scale of our registered images. The approximate scale of a pixel in the registered images was calculated by measuring the length of an airport runway in each scene. We expected our built-up area estimation would fall between the city-limits and urban-agglomeration estimates of the U.N., and this was observed for Chicago, Dallas, Las Vegas and Vancouver. The sprawling area we observed during photointerpretation of the San Francisco Bay area led to a built-up area estimate that far surpassed the United Nations urban agglomeration area.

During the period we studied, Dallas, Mexico City, Chicago and Las Vegas expanded at rates of a similar order of magnitude (18.3-53.8 km2 / yr) while Vancouver expanded at a rate of 4.9 km2 / yr and the San Francisco Bay area expanded at 136.1 km2 / yr. Some cities increased in built-up area disproportionately relative to their increase in population. For all cities other than Las Vegas, the expansion rate of built-up area exceeded the expansion of population, indicating urban sprawl. Las Vegas was an exception to this trend because of the number of discontinuous communities included in the urban agglomeration as redefined by the U.S. Census in 1994. Although the annual areal expansion of Las Vegas was comparable to other cities, its small initial size means that it tripled in area from 1973 through 1996.

These results illustrate the potential for further quantitative analysis of urban change using astronaut photographs. Our methods provide a less effort-intensive alternative to standard urban remote sensing techniques that would be appropriate for quantifying large-scale urban impacts on the landscape. They also are appropriate for research questions requiring analysis of numerous cities.

Citation for the published article

Robinson, J. A., B. McRay, and K. P. Lulla, 2000. Twenty-eight years of urban growth in North America quantified by analysis of photographs from Apollo, Skylab and Shuttle-Mir, in Dynamic Earth Environments: Remote Sensing Observations from Shuttle-Mir Missions (K. P. Lulla and L. V. Dessinov, eds.), John Wiley & Sons, New York, pp. 25-41, 262, 269-270.

Links to Color Images

	Figure 3.1 (A) The Greater Chicago area as photographed in 1973 and 1996 (NASA photograph SL3-46-199 and NM21-767-068). Small arrows indicate Merrill C. Meigs Field use for scale. (B) Dallas and Fort Worth in 1969 and 1996 (NASA photograph AS9-21-3299 and NM22-774-019). Small arrows indicate the Dallas/Fort Worth International Airport use for scale. (C) Las Vegas in 1973 and 1996 (NASA photograph SL3-28-59 and NM22-725-034). Small arrows indicate McCarran International Airport used for scale.
	Figure 3.2 Photographs of Mexico City in 1969 and 1996 (NASA photograph AS9-19-3011 and NM22-741-54B). These two images differed greatly in scale and look angle. It was still possible to georeference the images to one another. The inset shows detail from the 1969 image that has been rotated to match the orientation of the 1996 image. A sketch map illustrating the major canals and other distinctive features visible in the images. Small arrows indicate Licenciado Benito Juarez International Airport used for scale.
	Figure 3.3 San Francisco Bay Area in 1973 and 1996 (NASA photograph SL3-121-2374 and NM21-741-15A). These photographs were chosen over seta at more detailed scales to avoid the need to mosaic multiple images of such a large urban region. Small arrows indicate San Francisco International Airport used for scale. See also Figure 4.9.
	Figure 3.4 Vancouver, British Columbia in 1973 and 1996 (NASA photographs SL3-122-2512 and NM22-703-120). The original 1996 image was significantly underexposed, but detail for analysis was retrieved by darkroom lightening of prints and digital lightening of the digitized image. Small arrows indicate Vancouver International Airport used for scale.
	Figure 3.5 Built-up areas identified in 1969 or 1974 photographs (yellow) and 1996 photographs (red) overlaid on the registered and resampled image from NASA-Mir (1996): (A) San Francisco Bay Area; (B) Mexico City; (C) Vancouver; (D) Dallas; (E) Chicago; (F) Las Vegas.
	Figure 3.6 Comparison of urban land parcel sizes and IFOVs of satellite remote sensors with pixel sizes for the analysis of digitized photographs (1200 ppi) from low Earth orbit in this study. Urban parcel size represents the estimated size of a parcel of land that would indicate a single land-use class (Welch, 1982). Smaller pixel sizes then those observed in this study could be obtained by digitizing at higher resolution. For reference, the minimum ground resolved distance observed from the best astronaut photographs is also shown. (Modified from Welch, 1982: Fig. 4; also reproduced in Jensen, 1983: Fig. 30-32.)
	Figure 3.7 Comparison of 1990 urban areas estimated by a special United Nations survey (Demographic Yearbook, 1995) with the built-up area measured in this remote-sensing study. The lower edge of the white box indicates the city limits area and the upper edge indicates the urban agglomeration area (details of compilation in Table 3.1).
	Figure 3.8 Change in built-up area measured in this study compared to increase in population size as tabulated by the United Nations (Table 3.1). To facilitate comparison, data for all cities are presented at a uniform scale for population and area.
	Figure 3.9 Percentage change in built-up area and in human population (population data compiled from UN figures described in Table 3.1). The total percentage change has been annualized by dividing by the number of years between photographs.
	Figure 3.10 Comparisons of densities and changes in density computed by combining buit-up area measurements form this study with UN population data (Table 3.1). The number after each city name indicates the magnitude of change over the time period.

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