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morphology. Though the work was mainly done for scientific purposes, practical conclusions could often be drawn from these detailed geomor-phological studies. A geomorphological map of the volcanic island of Ternate (Moluccas) clearly revealed which parts of the surroundings were protected by ancient crater rims and relics of an old volcanic slope and which, to the contrary, were particularly vulnerable in case of an eruption. Geomorphology can certainly be extremely useful in the pro-tection from disaster by volcanic eruptions. A photo reconnaissance for geological purposes was carried out in New Guinea, at a ratę of 2000—3000 km² monthly. Major landform units could be distinguished but detailed observations, especially those of a lithological naturę, could not be derived from the photos. The field worker on the other hand, did a number of detailed observations, mainly located along river valleys and coasts. Without the use of airphotos, the extrapolation of his obser-vations to the not visited areas would apt to have been erroneous. The combi nation of field — and photo work was therefore particularly va-luable in this applied research, which dealt almost exclusively with the “static” aspects of geomorphology. An interesting example of dynamie photogeomorphology is a study carried out by L. H e r a t h at the in-ternational Training Centre for Aerial Survey, Delft, The Netherlands on the shoreline development of a part of the coast of Ceylon. He studied the changes of the coastline in the past from the position of old beach ridges and them estimated the futurę development. The longshore trans-portation of sand deduced as well as possible from the airphoto studies and some suggestions were madę as to the causes of the Coastal abrasion and its remedy.

The following uses can be madę from aerial photographs in gemor-phological research:

1.    Compilation of a preliminary geomorphological map of an as yet not reconnoitred area. The results of the photo interpretation can be transfered directly to the topographic map, if such a map is available. Otherwise a basemap has to be madę, e.g. by the slotted template me-thod.

2.    Preparation of the field work. The most interesting geomorphological phenomena can be located from the air and the trafficability of the terrain can be estimated. The most suitable traverses can thus be selec-ted. The field work can thus be planned efficiently which reduces the time and cost involved considerably.

3.    Extrapolation of results obtained by field work in a limited area only. This method is extremely useful and time saving when it is not possible or not essential to carry out a field check everywhere.

4.    Revision of existing geomorphological maps. It is often possible to add a considerable amount of detail and to inerease the accuracy of these maps.

5.    Detailed positioning during the field work and accurate plotting of sampling spots and other observations. This greatly enhances the relia-bility of the map prepared. The observations are marked by tiny holes and the annotations are madę on the back of the photo. An additional advantage is that freąuently the correct connection between the indivi-dual field observations then can clearly be seen on the photographs.

6.    Measurement of drainage density, height differences, relief energy, slopes, etc. Many morphometric problems are solved easiest by aerlial survey!

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