NUMERICAL ANALYSIS IN GEOMORPHOLOGY BY MEANS OF ELECTRONIC COMPUTER WITH REFERENCE TO EXAMPLES FROM SOUTHWEST JAPAN

Abstract

A general course of numerical analysis of topographic or in a broader sense geographic data is discussed here, assuming to use a high speed computer.
As long as a topographic map is employed as a common source of data, it is the first step to pick up numerical values from the map, and this generally requires a great effort. Once the data are obtained in the form of punched cards or tapes, it is rather easy today to process them by means of computer. A spatial analysis is now of great importance to geomorphologists and geographers in general who wish to interpret spatial interrelation or arrangement of landforms and other phenomena.
As examples of data processing by computer, the cases of a double Fourier (harmonic) analysis and a trend surface analysis are presented here, and the results are drawn by the XY plotter attached to the FACOM 270-30. The trend surface analysis is applied to the the Asan Mountains, Northeastern Shikoku. It gives a result which shows quantitatively a distinct contrast between the opposing sides of questa ridges developed on massive sand-stones which are constituent beds of the Cretaceous Izumi Group. The double Fourier analysis of topography of the Kinki District reveals that a dominant wave-length of 20-30km is of tectonic origin.
Processing the spatial data by computer is easy. What really matters is how to sake the effort required to take up numerous data correctly from the map. For this reason, it is desirable, in conclusion, to print a Cartesian co-ordinate grid on the map, as is the case in European and American maps. It is hoped further that a common data file concerning the informations read from the topographic maps is made to be available in the future.