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Ancient ports of Gujarat Marine trade had also flourished during the rule of Kshatrapa and Gupta kings. The capital of Maitrak kings, Vallabhi, was also a very prosperous port town during those days. The waters of the Gulf of Khambhat were not far removed from its gates and the city thus had sea communications. The former seaworthiness of the place is testified by the buoy that guards the entrance to the town even today and also by the copper plates found from different places during excavation. At present, the town is approximately 35 km away from the present seacoast and is completely landlocked. It is believed that the first vessels having sail were built at Kanakpur, Madhuvati and Bhadravati in Gujarat. As per saying, it is known that the speediest sail vessels were built in Samvat eighth century at Kanakpur. All these places are landlocked today.  Fig. 5: Soil marks in the IRS data of Gujarat Remote Sensing and Archaeology Archaeology is a science of the human past and its spread over space and through time. Remote sensing provides a snapshot perspective that iindispensable in today’s study of mankind. The utility of remote sensing is mainly for reconstructing historical geography as it provides confirmatory scientific evidences for the same, such as location and spread of palaeo-channels, palaeo-mudflats, settlements and agricultural area, etc. Aerial photographs were first used in 1921 for archaeological applications in North America. This marks the birth of archaeological applications of remote sensing. Remotely sensed data can be used for addressing problems associated with various types of site discovery, site prediction, preliminary reconnaissance and mapping of sites. The data can also be used for confirmatory evidences. The obvious significance of the information of remote sensing to the archaeologists is the problem of site discovery. Unfortunately, although the use of various forms of remote sensing data, primarily aerial data, has proven valuable as a means of site detection in other countries, archaeologists in India have not used remote sensing data for this purpose due to various constraints. Aerial data are generally not available of the required area and even if they are, their use is prohibited for general purposes for defence reasons. To get aerial photography done in India is a difficult task. To get the permission to fly over coastal areas itself is difficult. Further, even after getting the necessary permission from the Directorate General of Civil Aviation (DGCA), the aerial survey itself is time consuming. On the other hand, multi-date satellite data is easily available. Satellite data can successfully be used for archaeological applications. However, applications of orbital remote sensing data for archaeological uses have been limited in India. Application of Remote Sensing for Archaeological Site Location The archaeologist must know the location of sites. This information in itself can be valuable for studies in location analysis and settlement pattern. Given the current emphasis on viewing archaeological sites in a broad regional context, the synoptic coverage/overview provided by satellite data is of great value. Techniques that may be used to discover archaeological site locations from satellite data are:
On arid land with little plant cover and bare soil without any vegetation cover, the colour of the surface provides the most important, though not the only, means by which ancient structures may be detected. Marks on bare soil on cultivated land are also useful in detecting certain areas of archaeological interest. Colour variations of this type are caused by differences in the mineral and organic content of the soil. Partially obscured features may be revealed in arid regions. The positions of buried ditch fillings may be shown in some places by variations in the water content of the soil, which also affect its colour (Figure 5).  Fig. 6: Palaeo-Mudflats and strand lines on Gujarat coast Information on underground structures or positions of earth works may be shown by differences in vegetation growing on them, which may take various forms according to local circumstances. The vegetation may be greener on the ditches and paler on the banks, which shows different moisture content of the palaeo-channels, palaeo-mudflats or coastal areas. In arid areas, the scanty vegetation may similarly show the positions of ancient remains. Shrubs may grow in favourable places at the base of ruined walls, and vegetation may be denser in ditches but almost absent on the banks. Anomalous Landforms Occasionally, flood water outlines ancient earth works. They may protrude from a sheet of water on low ground or the water may fill the hollows. Wetter or drier patches may form above the buried features producing darker or lighter marks which are usually described as damp marks and when the soil dries, they fade out. An Example of the Use of Satellite Remote Sensing Data By delineating the strand lines based on remote sensing data along the SE Saurashtra coast, it is found that the shore line has been shifted more than once. One can also sea the wide streams with many tributaries end abruptly against these strand lines. The mud flats are related to the phenomenon of regression of the sea. They represent the sites of older mud flats when the sea level was several metres higher than the present, Figure 6.  Fig. 7: Flow of river Saraswati upto Rann of Kachchha |