More than 500 sheets of 15′×10′ quadangle 1:50, 000 landform classification map have been published in this three decades by the Economic Planning Agency (1956-74) and by the Prefectures (1971-, under the coordination by the National Land Agency), which come to cover about half of the whole national land area. Although 1/50, 000 scale landform classification map is convenient for rapid illustration of extentive area, it is not always appropriate to describe the fine-textured topography of mountains and hills in humid region as Japan.
Both aspects of large scale “detailed map” and of small scale “general view map” are required practically for the medium scale landform classification map. On every 1/50, 000 landform classification map, the 1st order boundary line has been drawn between the mountains or hills and the terraces or lowlands, and the 2nd order boundary line between the areas subdivided by relief class within the mountains and hills. The 3rd order topographic elements such as landslide area are represented by additional symbols or plan forms. The regions defined by relief (the current method) requires too broad boundary line, and the boundary to describe the inclination classes in the hillslopes (the alternative plan recently represented in some sheets) requires too intricated line on a 1/50, 000 map.
Careful investigation of various morphomentric paramenters using different-size grids concludes that the combination of relief value and valley frequency value in 40×40 grids of 15′×10′ quadangle or the product of the two values explains the details of the topographic characteristics of the mountain and hills in practical use. The relief in 40×40 grid shows the gradient of a small part of hills or of mountains and the valley frequency value represents the degree of roughness or smoothness of the land.