Regarding the influence of vegetation on the water balance in a drainage area, it is necessary to consider not only the dense growth of vegetation, but also the presence of dead grass and fallen leaves. Index of a) vegetation vitality rate and b) vegetation cover rate must be measured accordingly, showing quantitative analysis of vegetation changes. If the vegetation cover rate includes the amount of dead grass and fallen leaves covering the ground, the vegetation vitality rate and vegetation cover rate must be defined differently. We started measuring the annual changes in weeping love grass in May 1983, using a spectroreflectometer. We have been tried to define the vegetation vitality and vegetation cover rate using the changes of spectroreflectance of R(675nm) and IR (850nm) which are based on soil line, and their index are calculated. The results are reported herein.
Distribution of lineaments from the Landsat images around the Aso caldera shows good agreement with that of active faults which were found by geological investigations and photointerpretations. These active faults cut the Aso volcanic ash beds and sometimes the Akahoya ash bed which is the key bed indicating the age of about 6, 000 Y.B.P.. The lineaments elongated in ENE direction at southwest and northeast sides of the caldera correspond with the active faults which suggest the presence of the fracture zone that run under the caldera center. Macroscopic investigations of the image also show the distribution of major lineaments which are elongated in NNW, NW and NE directions respectively, and are 20-30 km long in the basement rocks found in surrounding areas of the caldera. These lineaments seem to reflect the presence of young faults resulted from the tectonic movement since the Pliocene.
The remote sensing techniques have been used for better understandings of the coastal sea aspects around the Beppu Bay. One of the Kuroshio branch current comes up to the Bungo Channel and enters the bay in winter. Then, it makes a coastal front between the mouth and the interior of the bay, while small scale eddies can be seen inside the front. A cold water flow from the Suo Sea possibly comes down along the Kunisaki Peninsula for the period from autumn to spring. The cold water would then come into the bay and cause a left swirling flow. For further observation, long period variations of the surface water temperature and salinity around the bay have been analized by a stochastic technique and discussed qualitatively.
Through the analysis of three and a half years' Landsat MSS imagery data, it was found that temporal variation of geometric distortion in the Landsat MSS data existed. Furthermore, it was also found that the variation is closely related to the stratspheric temperature above equatorial region with the correlation coefficient of 0.81. Based on this fact, it is considered desirable that infrared horizon model, the basis of the attitude determination, be modified adaptively in accordance with actual stratspheric temperature distribution. From the results obtained from geometric accuracy tests with a variety of the peak radiance from CO2 and half power height of CO2 radiance based on radio sounding data of a single station in a equatorial region, possibility of a slight improvement on the geometric accuracy of Landsat imagery data was confirmed.