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The Pennsylvania Power and Light Siting Problem

Perhaps GIS analysis will come through more convincingly with one more case study. This case is an applications demonstration, developed at NASA Goddard during the early 1980s, when its Eastern Regional Remote Sensing Applications Center (ERRSAC) still operated. The "client" was the Pennsylvania Power and Light (PP&L) Company, a public electric utility, whose service areas include parts of central and eastern PA. One service area is the state capital district at Harrisburg on the Susquehanna River that had been receiving much of its power from the infamous Three Mile Island, site of a nuclear, power-plant accident on March 28, 1979. This experience forced PP&L to have special concerns regarding any of its future sightings, for its own power facilities and for its large customers.

By the late '70s, PP&L had developed a computerized GIS database primarily for land use analysis, environmental impact analysis, energy facility siting, and other technical assistance. Its multivariate data base consisted of 43 data elements distributed in ten general categories, the two largest being terrain units and land use. These are shown in this table:

PP&L Multivariable File of Data Elements Table.

The standard grid cell size in this data base is 9.2 hectares (22.9 acres). The question prompting PP&L to approach ERRSAC in setting up a cooperative study: Can Landsat images help keep the GIS outputs up-to-date?

15-15: Landsat MSS resolution is equivalent to 1.1 acres. How did this fact influence PP&L in its thinking about utilizing space imagery in its geocoded data base? ANSWER

From these files, ERRSAC investigators used an ESRI software package to generate a 12-class map of the Harrisburg service area:

ERRSAC 12-class map of the Harrisburg, Pennsylvania, service area.Key to the EERSAC 12-class map of the Harrisburg service area.

The proof-of-concept task presented by PP&L for a Goddard-directed GIS analysis was to select the optimal site(s) for a heavy industrial complex. Two primary limitations were imposed: 1) the site must be within 5 km (3 mi) of a major source of water (the Susquehanna River met this condition), and 2) exclude areas in the immediate Harrisburg district.

The first step in the analysis was to generate a series of data element maps from the PP&L data base. We show here, six of the 23 produced:

PP&L "Landforms" and "Slope" data element maps.

These, and other, maps were helpful to the GIS interpreters and the planners in visualizing the distribution of variations within a given attribute. In the analysis, they stored the different categories within a theme and manipulated them by ordinal rankings in a numeric code.

15-16: Which, if any, of these maps could Landsat have made some direct contribution to, perhaps aided by supplemental information? ANSWER

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Primary Author: Nicholas M. Short, Sr. email:

Collaborators: Code 935 NASA GSFC, GST, USAF Academy
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