Archeological methodology and remote sensing.

We have shown that the different spectral surveying techniques and the resultant imagery vary in their applicability to archeological prediction and exploration, but their applications are far broader than we have indicated. Their full potential, to a considerable extent, still remains unexplored. Table 1 is a chart of the more common sensor systems useful to archeological investigators. Several kinds of photography, thermal infrared imagery, and radar imagery are listed. Checks in various categories of direct and indirect utility in archeological research indicate that the different systems do provide varying degrees of input for studies in these areas. Photography and multispectral photography have the broadest applications in this field. Standard black-and-white aerial photography generally serves the purposes of archeological exploration and site analysis better than infrared scanner imagery, radar, or color photography. However, the real value of remotesensing experimentation lies in the utilization of different instruments and in the comparison and correlation of their data output. It can be stated without doubt that there is no one all-purpose remotesensing device on which the archeologist can rely that will reveal all evidence of human occupations. Remote-sensing data will not replace the traditional ground-based site survey, but, used judiciously, data gathered from aerial reconnaissance can reveal many cultural features unsuspected from the ground. The spectral properties of sites distinguishable by various types of remote sensors may perhaps be one of their most characteristic features, and yet the meaning of the differential discrimnination of features has not been determined for the most part, since such spectral properties are poorly understood at this date. The difficulty in isolating the causes of acceptable definition in certain portion of the spectrum and the lack of acceptable definition in others suggests that the evaluation of remote-sensing devices discussed in this article is not always applicable to all environmental zones at all times and for all types of cultural features. The uncontrollable variables of terrain, ground cover, weather, types of archeological manifestations, and other factors all play an important role in the utility of the imagery to the archeologist. Factors within the control of the photographer or archeolgist, such as altitude, position of the sun, and the direction of flight, can greatly influence the utility of the sensor data. In addition, the variables should not be considered solely as they affect resolution. Resolution, per se, although an important photogrammetric parameter of remote-sensing imagery, is by no means the only important factor in data analysis. The synoptic overview, which is provided by aerial imagery, is frequently as necessary in interpretation as the spotting and identification of individual cultural features. Stated more simply, we might say: "To understand, one most certainly must see the forest as well as the individual trees." For maximum data retrieval, it is necessary that the archeologist attempt to utilize as many different types of remote-sensing devices under as many variable seasonal and climatic conditions as his resources and skill will allow. Only then he can select the most efficient system for the purpose in his area of study.