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Variability in Slope Measurements. A Discussion of the Effects of Different Recording Intervals and Micro-Relief in Slope Studies
A. J. W. Gerrard and D. A. Robinson
Transactions of the Institute of British Geographers
No. 54 (Nov., 1971), pp. 45-54
Stable URL: http://www.jstor.org/stable/621361
Page Count: 10
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Traditionally, slope-angle readings have been obtained by measurement between identifiable breaks of slope, but this method includes a large subjective element and imposes restrictions on subsequent analysis. As a result, it has become customary to construct profiles by recording the angles of successive short, constant intervals of slope. The recording intervals used by different workers vary in length, resulting in problems of comparability between different studies, since the angles recorded vary with the length of the recording interval and the micro-relief of the slope. This problem is illustrated with data obtained from the survey of eighteen slopes using 1.5 m, 3 m and 6 m recording intervals on Dartmoor, and thirty slopes using 2.5 m, 5 m and 10 m intervals in the New Forest. The slope-frequency histograms obtained show the marked effect that the different survey lengths have on the slope angles recorded. Marked differences occur in the maximum angles recorded and the modal slope classes obtained. Theoretical considerations and field measurement indicate that small protrusions have a noticeable effect on the measuring process, especially when low-angle slopes are surveyed over short recording intervals. To date, slope studies have made the tacit assumption that the variability of slope measurements is small. The results outlined suggest that this assumption is incorrect and this may lead to spurious correlations. This emphasizes the need to assess the variability and accuracy of slope measurements in geomorphological slope studies, and also to assess the variation in the measurement of other variables.
Transactions of the Institute of British Geographers © 1971 The Royal Geographical Society (with the Institute of British Geographers)