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During the early phases of the JRP, project personnel 
began to examine alternative methods of handling the large 
volume of Landsat data needed to conduct defoliation 
assessments on an annual basis. After much consideration, 
the decision was made to develop a Landsat-derived geo 
graphic data base which could be interfaced with image 
analysis software. As a minimum, the data base had to 
contain several data layers, including: (1) a Landsat 
digital mosaic of Pennsylvania exhibiting no defoliation 
and registered to the Universal Transverse Mercator (UTM) 
map projection, rotated to North and resampled to 57 meter 
square cells*; (2) a forest resources map (forest/non 
forest mask) derived from the Landsat data comprising data 
layer 1 above; and (3) digitized Forest Pest Management 
District boundaries and county boundaries registered to 
the Landsat mosaic. In addition, the capability to add 
additional data layers, such as the most recent Landsat 
data depicting defoliation conditions, was required. 
Figure 2 is a schematic diagram illustrating the 
characteristics of the Pennsylvania statewide data base. 
As previously mentioned, a key requirement associated with 
the creation of the data base was the capability to 
retrieve, digitally process and store the image data. 
Fortuneately, the necessary digital image processing 
capabilities already existed at a State-affiliated facility; 
namely, at the Pennsylvania State University Computation 
Center in University Park, Pennsylvania. Over the past 
decade, the Office for Remote Sensing of Earth Resources 
(ORSER) at Penn State had developed an extensive package 
of digital image processing software, and they were eager 
to enhance their capabilities through the development of a 
data base management system. Thus, a decision was made to 
develop and house the Pennsylvania statewide, Landsat data 
base on an IBM 3081 computer at the Penn State University 
Computation Center. Under the agreement, ORSER personnel 
were responsible for developing, acquiring, upgrading and 
implementing all software necessary to create and 
manipulate the data base. 
Creation of the Mosaic 
The creation of a map-registered Landsat digital mosaic 
for the State of Pennsylvania was the essential first step 
leading to an operational defoliation assessment system. 
This mosaic would provide a foundation for all subsequent 
processing and registration. The NASA/Jet Propulsion 
Laboratory (JPL) in Pasadena, California was requested to 
generate the initial Pennsylvania mosaic due to their 
demonstrated capabilities in generating Landsat mosaics 
for the states of California and Arizona (JPL, 1978). 
During this phase of development, ORSER acquired, 
implemented, and tested the necessary mosaicking software 
with JPL assistance, so that the registration of additional 
data layers could be accomplished at Penn State. 
*The 57 meter square cell was chosen because the standard 
cell size of MSS products in the Landsat-D era will be 57 
meters by 57 meters.