The author tried to estimate the water quality (Secchi disk transparency) of Lake Kasumigaura and other lakes in the northern Kanto plain by means of multivariate analyses and computer mapping techniques. The results of this estimation were as follows. 1. The water quality estimation models were derived from the multiple regression analysis of LANDSAT and ground truth data in Lake Kasumigaura (Jan. 19, 1980). 2. Among these models, the Secchi disk transparency estimation model retained the highest ratio of contribution and the signal in band 6 was adopted independent variable of the model. 3. It is quite difficult to fit this model to the data of the oligotrophic lakes for such reasons as weak energy penetration of the near-infrared wave-lengths and restriction in the model itself. 4. On the other hand, it is possible to apply this model to the data in Lake Kasumigaura and other eutrophic lakes, of which the transparency are below 1.59m and located in the lowland. 5. In Lake Kasumigaura the estimated transparency (Secchi disk transparency) reduced from the center or the areas adjacent of the outlet to Tsuchiurairi and Takahamairi estuaries. 6. In Lake Kitaura the estimated transparency reduced from the southern part of the lake and its value was relatively higher than that of the center of the lake Kasumigaura. 7. In Lake Hinuma the estimated transparency had uniform pattern with the same value as that of the central part of Lake Kasumigaura. 8. There might be two approaches in the future application of regression analysis into satellite remote sensing of lake water pollution. The one is to get optimal regression using numerous ground truth data in various lakes and to amend the model for each lake depending upon each circumstance of the lake. The other is to cluster various lakes into a few groups which have similar physical and chemical conditions before the application of the analysis, and store the water quality estimation models for each group. For the practical purpose, the latter seems to be more preferable than the former. 9. The ground truth observations might be carried out efficiently after the derivation of the model, but the collection of a few kinds of data would be required for the corrections of the video data.
The study of urban factorial ecology has become popular among Japanese geographers because this is one of the most useful methods for analyzing basic urban residential dimensions and structures. This field of study in Japan, however, takes little consideration of the results of traditional studies of urban residential structures. The first point at issue in this paper is the spatial and social significance of the two main ecological factors, i.e., socio-economic status and family status. Since the spatial patterns of socio-economic status factor are arranged by sectors, these are coincident with the sactorial patterns of high status residential areas by Hoyt. Thus, it is necessary to explore the relationships between the spatial patterns of socio-economic status by the factorial method and those of high status residential areas by the traditional method. Family status factor displays concentric patterns and, therefore, the areal patterns of age structures and life cycles need to be investigated in detail. The second point at issue is the study of ecological change through time. This kind of study can be approached by two analytical methods: cross-sectional analysis and longitudinal one. The former is a comparison of ecological structures between two time periods, and the latter is a matter of ecological change through time. Since the longitudinal analysis compares the differences in the rate of change of variables between two time periods, the amount of variation of variables which can be explained by factors is smaller than that of the cross-sectional analysis method. Thus, it is necessary to select a proper analytical method by considering the relative merits of various measures of change. In view of the length of time for analysis, the study of ecological change is divided into short-time studies and long-time ones. The former is to explore the uniformly continuous change in recent time, the latter is to explore the historical change over a long period of time, which is especially related to the problem of the historical residential development. In order to analyze the residential structures in Japanese cities synthetically, the results of factorial ecological studies are to be discussed in comparison not only with the results of the earlier studies in the U. S. A. which possesses the typical ethnic differences, but also with the results in the other countries which possess little ethnic differences in terms of residential structures. Moreover, it is necessary to explore the complex interrelationships between ecological factors and residential structures by traditional method, and also to formulate the model of historical residential developments in Japan.