and non-standardized within and among the states involved 
in the programs. A new survey technique which could 
provide timely, accurate and standardized assessments at a 
reasonable cost was needed. In the mid-1970's, researchers 
began to look at Landsat multispectral scanner (MSS) data 
as a potential survey medium for monitoring widespread 
forest disturbances such as that caused by insect 
infestations. The spectral, spatial, temporal and synoptic 
coverage that Landsat could provide in a standardized 
format seemed to make it an ideal survey medium. Scientists 
at the National Aeronautics and Space Administration's 
(NASA) Goddard Space Flight Center (GSFC) in Greenbelt, 
Maryland were among the early participants in this area of 
research. In 1979, a Joint Research Project (JRP) was 
initiated between NASA/GSFC and the Pennsylvania Bureau of 
Forestry/Division of Forest Pest Management (BOF/DFPM). 
The JRP was designed to demonstrate the usefulness of 
satellite remotely sensed data for monitoring insect 
defoliation of hardwood forests in Pennsylvania. 
The assessment of forest insect defoliation over an area 
as extensive as Pennsylvania required the processing and 
storage of large volumes of satellite and ancillary data. 
Therefore, a major effort within the project involved the 
development of a map-registered, statewide Landsat digital 
data base for Pennsylvania. The data base needed to be 
interfaced with image analysis software by means of a data 
management front-end system, so that an automated 
assessment of defoliation damage could be conducted within 
user-specified geographic areas. A complete description 
of the data base which was developed will be given in this 
paper, as well as a brief discussion of the data management 
front-end system. Turner and Baumer (1982) provide a more 
complete discussion of the data management system. 
BACKGROUND 
The Gypsy Moth 
The gypsy moth larvae defoliate large tracts of hardwood 
forest in the Northeast, feeding on oak, alder, apple, 
basswood, willow, and birch foliage. Excessive population 
pressures can expand the caterpillars' diet to include 
coniferous species, such as hemlock, cedar, pine, and 
spruce, as the insect reaches maturity in late June and 
early July. The insects overwinter as eggs and emerge in 
late April or May. Feeding begins immediately; each 
successive instar devours larger quantities of leaves. 
The effects of their voracious appetites become noticeable 
in early June. By the end of June, two months after 
hatching, the larvae are over two inches long and are 
easily identified by the five pairs of blue spots and six 
pairs of red spots arranged in two rows along the back. 
These larvae consume massive amounts of vegetation, and 
defoliation reaches its peak by early July. The cater 
pillars then pupate, and in ten days emerge as moths. The 
gravid females, unable to fly, produce pheremones to attract 
their mates. The females lay from 200 to 800 eggs in a 
single mass on any convenient surface.