Effects of Technological Change on Relief Representation on USGS Topographic Maps

Abstract

In 1882, the United States Geological Survey began its National Mapping Program 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. Though older maps are a fascinating source, the use of data collected from historic USGS topographic maps in modern applications necessitates a general knowledge of their potentials and limitations. This study compares representations of terrain features on historic maps compiled using plane table methods with the same features as represented on more accurate modern maps compiled using photogrammetry. Using the modern map as a standard, errors in the old maps are identified and defined. Measures of closed contour lines record 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 relates errors to these geometric components of contour lines. Due to practices of smoothing and generalization of contour lines in plane table surveys, measures of both angularity and shape are significantly different between older and newer maps. Systematic errors, a consistent displacement of contour lines in a similar direction, are also identified on the historic maps.

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