The influence of seasonal factors on the recognition of surface lithologies from ERTS-imagery of the western Transvaal

The value to geological studies of repetitive ERTS-imagery was investigated by comparing two images gathered during different seasons over an area in the western Transvaal Province of the Republic of South Africa. The first of the two images (1050-07355) was gathered on September 11th., 1972, co-inciding with the end of the dry winter season. The second image (1158-07363) was gathered in the middle of the summer rainfall season on December 28th., 1972. A comparison of the two images reveals striking differences in the amount of recognizable geological detail. The differences exhibited by the two images clearly demonstrate the importance of repetitive ERTS coverage in geological investigations, particularly in areas of marked seasonal variations.