地下水調査の際地盤高度を地形図から読みとる場合の精度について

概要

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On making ground water table map, it is needed to have the value of ground height. On a preliminary survey, one sometimes uses the value from map reading instead of that from leveling. The author wants to know the accuracy of the value from map reading. He carried on his survey on Kisogawa fan-like delta plain, Oomama fan-like upland, Kinugawa alluvial plain and Yumihama sand bar areas. He selected many points on these districts and measured the heights by leveling (G. H.). Then he checked these heights on topographic maps having the scale of 1 : 25, 000 and that of 1 : 50, 000 (G. H. 2.5 G. H. 5.0) respectively. Reading the differences between the value of leveling and that of map reading on each scale of maps (X2.5, X5.0), he calculated the mean X2.5 and R5.0. Then he estimated the range of mean taking confidence factor as 95 %. As to the absolute value of mean, there is no signifigant difference between the value from the map of 1 : 25, 000 and that of 1 : 50, 000. The range of the distribution of mean value from the map of 1 : 25, 000 is 1.0 meter and less than that from the map of 150, 000 amount to 1.5 meters. Generally speaking, ground height from map reading can be used for making water table map with contour interval of 2 meters on flat areas.
社団法人東京地学協会の論文