In 1882, the United States Geological Survey began its National Mappping Program designed to
map the nation using a series of several thousand topographic quadrangles. Since that date, the
program and the maps themselves have undergone many changes due mainly to technological advances
in mapping methods. The use of data collected from historic U.S.G.S. topographic maps
in modem day applications necessitates a general knowledge of the potentials and limitations of
these data. This study compares representations of terrain features on historic maps compiled using
plane table methods with the same features as represented on more accurate modem maps compiled
using photogrammetry. Using the modem map as a standard, errors in the old maps were identified
and defined using statistical procedures. Measures of closed contour lines recorded the angularity
of the line, the length of the line, the area within the contour, the shape of the feature and spatial
relationships between contour pairs. The analysis attempts to relate errors to these geometric
components of contour lines and to predict the occurrence of error. Due to practices of smoothing
and generalization of contour lines in plane table surveys, measures of both angularity and shape
were significantly different between older and newer maps. Systematic errors, a consistent displacement
of contour lines in a similar direction, were also identified on the historic maps. Based
on these results, several suggestions for continuation of the research are given.
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