Excerpt: Pietrusko on Remote Sensing of Populations

In a new book from De Gruyter, Technical Lands: A Critical Primer, alums Charles Waldheim (MArch’89) and Jeffrey S. Nesbit (MArch’09) examine the concept of “technical lands”: spaces united by their exceptional status and ranging from disaster and demilitarized zones to prison yards, industrial extraction sites, airports, and spaceports. Associate Professor of Landscape Architecture Robert Gerard Pietrusko and Billy Fleming, the Wilks Family Director of The Ian L. McHarg Center for Urbanism and Ecology, contributed essays. In an excerpt from his essay, “Census and Sensing,” Pietrusko discusses the ways that data collected from NASA’s Landsat civilian satellite begnning in 1971 affected the representation of cities within land-use and land cover datasets, leading to a new era of remote sensing and population measurement. 

The McHarg Center is organizing a book talk with the authors on October 19, 2023.

Civilian Reconnaissance

Throughout the 1960s, there were multiple collaborations between the US Geological Survey (USGS) and the CIA, where projects that tested novel forms of reconnaissance also had potential usefulness for domestic applications.(1) In fact, the interaction between intelligence agencies, the USGS, and other civilian departments was so active that by the end of the 1960s, a committee was initiated within the CIA to manage the frequent exchanges of information.(2) It is in this general environment that the Geographic Applications Program (GAP) was established and funded by NASA in 1966. Program director Arch C. Gerlach clearly stated his ambition to continue these collaborations. While planning the program, “[Gerlach] had contacted key individuals in the Central Intelligence Agency and Defense Intelligence Agency and had received tentative assurance that one or more experts working on classified projects will assist in planning geographic research projects.”(3) Shortly after the program’s official launch, the CIA’s deputy director of basic and geographic intelligence was appointed to the GAP’s advisory committee.(4)

Like the dualities in the more extensive Landsat program, the GAP created remote sensing techniques used for gathering intelligence across the globe that might be useful for civilian applications. They hoped to convince US academics, urban planners, and policymakers that Landsat data was helpful in the management of urban areas.(5) They reasoned that a demonstration of domestic uses for remote sensing at home—and their adoption by US municipalities—might reduce foreign apprehension about satellites invading their airspace and photographing their cities.(6) A 1965 conference on the use of spacecraft in geographic research created the GAP blueprint and acknowledged its international implications. “The fact that many of the sensors were developed and perfected for purposes of military reconnaissance,” the organizers wrote, “is a psychological disadvantage.”(7) After a series of collaborative missteps in Vietnam with the Department of Defense, NASA was also struggling to establish Landsat’s civilian relevance and assure foreign nations that the program was not, in fact, a covert military operation.(8) Therefore, when Robert Alexander, head of GAP research, described the program’s ambition “to improve the habitability of this planet by monitoring surface environmental conditions and changes,” he aligned the GAP with NASA’s PR campaign for the Earth Resources program more generally.(9)

Through the 1970s, GAP researchers created several pilot projects to demonstrate Landsat’s capabilities. Among these was the Land Use and Land Cover (LULC) Classification System for Use with Remote Sensors, a taxonomy for translating the tones and textures of Landsat images into discrete land-use classes.(10) In accordance with the program’s focus on natural resources and urban analysis, its designers argued that the lack of land-use information in cities resulted in chaotic urban growth; new development, when not properly planned, might cover subsurface mineral deposits or negatively impact fertile agricultural soils.(11)

The system was conceived ahead of Landsat’s launch in 1971. It contained nine general land-use categories that were updated and republished after five years of study by the GAP.(12) The categories were intended to be deployed over the entire earth, disciplining its surface variation into a single technical system of comparable polygons, whose relative areas could be measured, tabulated, aggregated, and analyzed for a variety of managerial purposes. GAP researchers assessed the efficacy of the categories during several pilot projects, and many alterations were proposed in the process. Notably, the categories were not evaluated for their representational correspondence to land uses as they might appear on the ground.(13) Instead, researchers evaluated how easily the categories could be deciphered within satellite images or how smoothly they articulated specific practices of urban and territorial analysis. Consequently, the meaning of the categories was determined by technical workflows within the pilot projects used to assess them. As I will show in the following section, studies like the 1970 Census Cities Project reduced the category “urban” to a quantitative measurement of changing population density.

Urban Change Detection

The Census Cities Project (also called the Census Cities Experiment in Urban Change Detection) (14) was directed by geographers Robert Alexander and James Wray. Their goal was a “combined use of sensors and census” through which changes in land use and population density could be measured over time.(15) Tracking these changes, they argued, would provide rapid information to urban planners about the status of their city’s economic development and populace.(16) In 1970, the GAP commissioned NASA airplanes to gather high-altitude imagery over twenty-six US cities, or “test sites.” Using GAP’s LULC scheme, the team classified the images into land-use categories and drafted the boundaries onto mylar maps for easy measurement and analysis. As Robert Alexander described, the map was only part of the final product; more important was what the land-use categories indicated—and what an analyst could infer through them. The patterns within the images and the categories assigned to them were proxies for other urban information that was of the genuine interest of the researchers.(17)

Interpreters analyzed the patterns of urban form but not in their own right; instead, what interested them was what these patterns indicated—urban population density. The GAP and NASA timed the photo missions to be contemporaneous with the 1970 decennial census. The simultaneous collection of aerial imagery and statistical data allowed researchers to make visual-numeric correlations between land-use patterns in the photographs and demographic enumerations on the ground. Once the land uses had been mapped, they were associated with the underlying census information—most notably, the population counts. The result was a baseline from which future aerial images could be visually interpreted and quantitatively described. They developed this approach anticipating Landsat’s frequent overflight, which captured images of the cities every eighteen days. They reasoned that the repetitive coverage would allow them to detect small changes in photographic patterns over time. Since these photo patterns were associated with land uses, researchers could measure the area of an observed change and calculate a new population estimate. Up-to-date information would then flow into urban management practices that were seemingly made more efficient as a result.

Despite the project’s stated goals, it was indifferent to the specific conditions of US urbanization in the 1970s. For example, New York, Chicago, and Los Angeles were omitted from the study despite their large extents, dynamic land uses, and complex planning issues.(18) The project also had an a priori assumption of remoteness; it was seemingly most useful physically inaccessible cities.(19) Researchers did not consider implementations of the project where land-use categories were confirmed on the ground or connected to specific planning processes.

Two years after Landsat’s launch, Alexander and Wray’s resultsconfirmed these assumptions and the project’s poor fit for US cities. Using Landsat’s high-altitude imagery, they could not identify “intra-urban land uses” or detect their changes.(20) From the standpoint of an urban management strategy, these identifications were a necessary precondition, and the project was seemingly a failure.(21) However, these findings were not presented as detrimental within the project report. Instead, they implied a different use of the technology. Though changes internal to a city could not be detected, Wray wrote, the pattern of urban growth could be, and this allowed them to successfully “define urban expansion, project future population densities, and assess the environmental impact resulting from gradual and catastrophic changes.”(22) As a result, no land-use changes were measured, only the size of a generalized urban condition, and most notably, those that appeared to be growing. But within a US context, this too was an unnecessary use of the technology. Once describing the importance of the project, Alexander cautioned that “there is a finite limit to the number of people who can be accommodated in any given region without causing an irreversible change in either the environmental or the supporting social systems.”(23) Despite the alarming language, it was a poor description of US cities in the 1970s when metropolitan areas rapidly lost people to the suburbs. Even Washington, DC—the main site of their study—shrank by 118,117 people between 1970 and 1980.(24) While seeming evidence of a poor understanding of US cities, the misalignments between the GAP’s stated goals and the project’s domestic usefulness communicates something else entirely: the Census Cities project was intended to be used in locations other than the census cities themselves. Therefore, it was not urbanization—with all its complexity and specificity—that the Census Cities Urban Change Detection Project monitored, it was “urban” as a nominal label that quantitatively indicated a density of bodies. This result pointed away from domestic uses of the technique and instead towards foreign countries now accessible through Landsat imagery, where growing populations were seen as potential risks for US national security.

1) For instance, a 1963 study that used infrared cameras to detect underground volcanic heat sources in Hawai‘i was designed in collaboration with photo-intelligence officers who hoped that the technology would allow them to detect nuclear weapons hidden in Cuba. See Dino Brugioni, “The Serendipity Effect,” Studies in Intelligence 14, no. 1 (Spring 1970): 60.

2) “Minutes of the ARGO steering committee meeting of 10 June 1968,” General CIA Records Collection, doc., CIA RDP80T01137A000200060034-6, CIA FOIA Reading Room, accessed June 1, 2021, https://www.cia.gov/readingroom/document/cia-rdp80t01137a000200060034-6.

3) “Minutes of the forty-first meeting of the Committee, Dec 16–17, 1965,” Archives of the National Academy of Sciences, Division of the National Research Council (DNRC), Earth Sciences, Committee on Geography Advisory to the Office of Naval Research.

4) Deputy Director, Basic and Geographic Intelligence, “Memo: Participation on a National Academy Advisory Committee, 13 September 1967,” General CIA Records Collection, doc., CIA-RDP79- 01155A000300020115-8, CIA FOIA Reading Room, accessed June 1, 2021, https:// www.cia.gov/readingroom/document/cia-RDP79-01155A000300020115-8.

5) NAS-NRC Committee of Geography, Advisory to the ONR, Spacecraft in Geographic Research (Washington, DC: National Academy of Sciences and National Research Council, 1966); NAS-NRC, Useful Applications of Earth-Oriented Satellites. (Washington, DC: National Academy of Sciences and National Research Council, 1969).

6) For an in-depth treatment of the transfer of aerial sensing technology from military to civilian applications, see Jennifer S. Light, From Warfare to Welfare: Defense Intellectuals and Urban Problems in Cold War America (Baltimore, MD: Johns Hopkins University Press, 2005).

7) NAS-NRC Committee of Geography, Spacecraft, 20.

8) Neil M. Maher, Apollo in the Age of Aquarius (Cambridge, MA: Harvard University Press, 2017), 54–91.

9) Robert H. Alexander, “Geography Program Review and Integration,” Second Annual Earth Resources Aircraft Program Status Review, NASA Manned Spacecraft Center, Houston, TX, September 16–18 1969, National Aeronautics and Space Administration (Washington, DC: US Government Printing Office, 1969), 322–23.

10) James R. Anderson, E. E. Hardy, J. T. Roach, and R. E. Witmer, A Land Use and Land Cover Classification System for Use with Remote Sensor Data (Reston, VA: US Geological Survey, 1976).

11) Anderson et al., Land Use and Land Cover, 1–2.

12) It also contained thirty-six subcategories, but these were intended for images gathered at roughly 40,000 feet, far below Landsat’s altitude; Anderson et al., Land Use and Land Cover, 2.

13) Anderson et al., Land Use and Land Cover, 5; see Robert Gerard Pietrusko, “The
Surface of Data,” LA+ Journal of Landscape Architecture 4 (Spring 2016): 78–85.

14) James R. Wray, “A Preliminary Appraisal Of ERTS-1 Imagery for The Comparative Study of Metropolitan Regions,” Earth Resources Technology Satellite-1 Symposium Proceedings, Goddard Space Flight Center, Greenbelt, MD, September 29, 1972 (Washington, DC: US Government Printing Office), 95–99.

15) James R. Wray, “Census Cities Project and the Atlas of Urban Regional Change,” Proceedings of The International Workshop vol. 2, 343. 

16) Wray, “Census Cities Project.”

17) Robert H. Alexander, Central Atlantic Region Ecological Test Site, Final Report Vol. 1 (Reston, VA: US Geological Survey, 1979), 251.

18) US Census Bureau, 1970 Census—Population and Land Area of Urbanized Areas for the United States, PC(S1)-108 (Washington, DC: US Census Bureau, 1979).

19) For instance, the GAP’s first publication on land-use classification presented a scheme stating that the only source of information would be remotely sensed imagery. James R. Anderson, “Land-Use Classification Schemes,” Photogrammetric Engineering 37 (April 1971): 379–87.

20) Harry F. Lins Jr. and James R. Wray, Urban and Regional Land Use Analysis: Carets and Census Cities Experiment Package: Monthly Progress Report (April 20, 1974).

21) At the 1971 International Workshop, for instance, Wray presented a speculative proof-of-concept that mapped changes at a detailed urban scale. See Wray, “Census Cities Project and the Atlas of Urban Regional Change.”

22) Lins and Wray, Urban and Regional Land Use Analysis, 3.

23) Alexander, Central Atlantic Region Ecological Test Site, 291.

24) Brian J. L. Berry and Donald C. Dahmann, “Population Redistribution in the United States in the 1970s,” Population and Development Review 3, no. 4 (December 1977): 443–71; US Census Bureau, 1980 Census of Population—United States Summary, PC80-1-A1 (Washington, DC: US Department of Commerce, Bureau of the Census, 1984).