The application of Land sat imagery to Geomorphologic Mapping in the central plain and northeast plateau for soil survey purpose.

Pongpit Piyapongse
Chief, Soil and Water Research Branch, Technical
Division, Department of Agriculture

Abstract

The objective of this study is to test the possibilities and apply remote sensing techniques, especially the use of synoptic view of LANDSAT imagery to geomorphological mapping for soil survey purposes. Various visual interpretation methods namely, diazochrome techniques, multiband additive viewer, false color composite and field checking have been employed in this study. The results obtained provide information for the following conclusions.

1. LANDSAT imagery false color composite at the scale of 1:250,000 could be used effectively as a base map for land form patterns identification.
2. The 1:250,000 false color composite could recognize the following basic categories.
   1. Land use patterns.
   2. Macro-form types under consideration of their morphostructures.
   3. Landform classification morphologically.
   4. Lithology and drainage patterns.
   5. Soils differentiation at Great Group level
      1. There is direct correlation between landform pattern and soil genesis.
      2. LANDSAT Imagery is very useful to delineate soil boundaries, especially the one that conform to landform patterns.
      3. Soil moisture regime could be recognized clearly between moist, dry and under submerged conditions, using LANDSAT imagery band 7 (0.8-1.1 micarometer).
      4. The use of automatic data processing should be emphasized for future soil survey and mapping.
      5. The future LANDSAT with higher resolution elements will give us more detail about landforms and soil information.

1.Introduction

The need for geomorphological map at present time is increasingly high. Although geologists, soil scientists, geomorphologists, ecologists and other related fields have represented geomorphological information on base maps for many years, the concepts of geomorphological mapping as a discipline within the science of geomorphology is merely a post-war development.

Several countries in Europe have developed many geomorphological mapping legend, namely the Belgian, the Netherland legend, the French legend and the Russian legend, but no effort has been made to correlate and adjust those legends to be used as an international legend. The American legend could be used effectively in the American continent. In tropical region we have to add many new legend into the maps for soil forming factors and soil forming processes are quite different from the temperature zone.

2. Methods and Procedure

LADNSAT imagery falser color composites at 1:250,000 scale have been used in this study. The categories being studied included the identifications of macro landforms, morphographic, morphometric, geo-chronology, morphogenetic and lithologic data obtained from field works and from geologic map of Thailand.

The study included the following steps of observations.

1. Rapid scanning of the image coverage which reveal the general relationships of landforms, soils and lithology.
2. Production of a topographic base with drainage pattern and lithologic data plotted on it, by using topographic map transparency overlay and geology map of the same scale.
3. Analysis of all available sources of information about the study areas.
4. The production of preliminary map.
5. Spot check for ground information data collection.
6. Adjustment of soil boundaries into landform boundaries.
7. Enhancement of the final map.

3. Results and Discussion

The results of preliminary study indicated that, we can use LANDSAT imagery in soil survey work effectively. The areas of high soil moisture content can be seen clearly from LANSAT imagery band 7. The areas of macro landforms which could not be recognized from aerial photograph at 1:15,000 scale can be seen clearly on only one frame of LANDSAT imagery which can cover the areas of 185x185 kilometers. The alluvial fans in many provinces in the Central Plain could be identified clearly. The Karst corrosion plain in the Central Highland could be recognized. The Plateau and structural plain could be separated from the flood plains. Coastal peneplain could be identified clearly in the Southeast coast. Generally speaking, to summarize what we found in this study confirmed that we can use LANDSAT imagery to enhance our present soil maps with more confidence and more effectively. With the use of LANDSAT imagery, we could establish world soil map at easier task, for LANDSAT imagery can provide us with better synoptic view to cover larger areas of study.