人口分布図に関する研究

抄録

To discuss population problems, it is very important to grasp the geographical distribution of various factors pertaining to the population phenomena. In this paper the cartographic representation of absolute and relative distribution of the population-as these are the most fundamental facts of the population problems-are treated.
This study has been done accompanying with the compilation of the “Population, Japan, series of Geographic Maps of Japan” (1 : 800, 000) No. 7, published by the Geographical Survey Institute, Ministry of Construction.
Referring to various population maps which have already been made in many countries, the writers made tentatively various sorts of maps showing population distribution, particularly for the scale of 1 : 800, 000. So, simultaneously, the writers had to try to clarify the expressive ability of this small scale map.
Here the writers tried to do some consideration about the distribution maps as follows :
Fig. 1 Population Distribution : In this map the population distribution is represented by dots of uniform size. Each dot represents 500 persons. The size of dots and the given quantity of each dot are determined after some trials. The placing of dots must be done with an understanding of the distribution of population.
In order to place each dot on proper point, the writers used the “Land Use Map” of the same scale
Fig. 2 Urban Population : This is one of trial cases for representation of urban population by shares. Urban population was calculated as follows : Urban population, = (total population of the city) × (urban population ratio) Urban population ratio= {(total of employed pop.) - (agricultural pop.+forest and logging pop. +fishery and aquaculture pop.+ mining pop.)} ÷ (total of employed pop.) The cubic root of shares is proportionated to the urban population. The rural population is represented by two sorts of dots varying in size and in given quantity, each small dot represents 500 persons and the other 2, 000 persons.
These spheres occupy much less space than the circles of corresponding size, so the writers tried to represent the population of agglomerated areas by this system, on the choropleth map of population density.
But the experiments to represent whole country in such way have not shown good result, because partially of the intricacy of representation and partially of the cartographic difficulty. Fig. 3 Distribution of Population Density : This is a choropleth map of population density.
To determine density classes, the representation of regionality is especially concerned, so as to one can recognize regional features of this country by the patterns of each class. While, the meaning of population density is especially great in rural area, so the lower classes are classified in narrower ranges. The area where the density is more than 1, 000 persons per 1 square k.m. may be treated as the urban area. The frequency of 11 classes is shown in Table 2.
Fig. 4 Isopleth Map of Population Density : This map shows the distribution of population density by isopleths. In this case isopleths are transformed from the choropleth map (Fig. 3) taking into consideration the topography and population distribution (Fig. 1). Boundaries between lowland and mountainous areas are represented by the dotted lined. The lowland areas are defined as where the inclination of the land surface is less than one twentieth. By representing the boundaries of lowland areas on this map, the various patterns of distribution of population density in these areas will be recognized.
Fig. 5, Fig. 6 These are isopleth maps of population density. Two drainage areas of Sai-Kawa and Niyodo-Gawa are chosen from the standpoint of view where the representation of population density is very difficult by the above mentioned methods.