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Drumlin measurements: a test of the reliability of data derived from 1:25000 scale topographic maps

Published online by Cambridge University Press:  01 May 2009

J. Rose
Affiliation:
Geography Department, Birkbeck College, 7–15 Gresse Street, London, W1P 1PA
J. M. Letzer
Affiliation:
Geography Department, Birkbeck College, 7–15 Gresse Street, London, W1P 1PA

Summary

Measurements have been made on drumlins from the Glasgow district and eastern Westmorland, using 1:25000 topographic maps and direct field mapping. Comparison of the results suggests that topographic maps provide data which varies in accuracy with the clarity of the drumlin pattern depicted by the map, and the character of the particular descriptive parameter. Dimensionless parameters such as elongation ratio, tapering value (k), and stoss-point ratio are most accurately estimated, but size, spacing and density are consistently inaccurate, and the number of drumlins recognized is, at best, only 50 % of the number of drumlins that exist in the field. It is suggested that topographic maps fail to give information at the precision level required for the analysis of this type of glacier bedform.

Type
Research Article
Copyright
Copyright © Cambridge University Press 1975

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