Image selection, and mapping of IUA's 
An archival DMSP image obtained over eastern United States at 
approximately 9:00 pm on February 15, 1975 was selected for initial 
investigations. This image was carefully duplicated (¥= 1) in order to 
faithfully preserve the original tones and provide a transparency which 
could be used for the analyses. By correlation of the image with the 
population map, seventeen IUA's recorded as reasonably symmetric bright 
spots were selected for mapping and microdensitometer analysis. These 
IUA's represent urban areas with 1970 populations of 20,000 to over 
1,000,000. A Bausch and Lomb Zoom Transfer Scope was then employed to 
transfer the image boundaries of the IUA's to base sheets of 1:750,000 
scale. These boundary plots represent the basal planes required for 
construction of IUA domes. 
Microdensitometer analysis 
Each IUA was carefully scanned (at 20:1 gear ratio) with a Joyce 
Loebl Mk III CS microdensitometer to generate density profiles at 
1:750,000 scale along predetermined x, y grid lines. The grids (x-y 
profile axes) were then fitted to the maps of the IUA boundaries and the 
density (z) values for each grid intersection determined by interpolation. 
These x, y, density (z) coordinates define the three dimensional represen- 
tations of each IUA and were constructed in perspective with the aid of 
a Calcomp THREE-D software package operational on the University of 
Georgia IBM 370/158 computer system (Figure 7). These drawings permit 
qualitative visual comparisons of the energy utilization patterns of the 
urban areas. 
Quantitative IUA-energy consumption relationships 
Three categories of data have been employed to establish quantitative 
relationships between population, energy consumption and IUA dome volume. 
1. 1970 populations of the urbanized areas (defined according to 
Bureau of Census criteria as a central city with a population of 
50,000 or more and surrounding closely settled territory) of the 
major cities and the incorporated limits of cities of less than 
50,000. 
2. 1975 energy consumption data in kilowatt hours (kwh) supplied by 
the utilities responsible for the 17 cities. In general, the 
power consumption data refer to the approximate urbanized areas or 
corporate limits. However, variations in areal jurisdictions of 
utilities do introduce a bias of unknown, but apparently minor 
significance at the small mapping scales. 
3. IUA dome volumes in mm3 computed with Simpson's Rule: 
V = h/3 (Ag + 4A1 * 2A9 + 4A3 + 2A4 * --- + 2An-2 * 4An-1 * An) 
h = grid spacing of microdensitometer profiles 
area under each microdensitometer profile measured in 
mm? with a digital planimeter 
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A 
Scattergrams were constructed on various types of graph paper to 
determine if significant relationships between the data sets could be 
discerned. As with the previous example, doubly logarithmic paper proved 
most suitable, with strong linear relationships exhibited for population 
vs. kwh, population vs. IUA dome volume, and kwh vs. IUA dome volume.