Application of remote sensing techniques in geological of mapping Nairobi-Kajiado-Machakos area

Abstract

The study deals with the applicallication of space images in geological mopping of the Nairobi-Kajiado-Machakos area. A visnaI jnterpretation is made. The spectral analysis is mnde usinq standard photographic faJse colour composites (FCC) and black and white satellite imageries. In the visual image analysis, linear features that were observed both in small scale (1:500,000) and large scale (1:125,000) are described. A discrimination of the geology on the basis of the radiometric or tona1 signatures is also made. The linear features to the west of the area are a result of tectonic activities in the East African Rift System that lead to faulting of the rocks. These linears correspond to faults. The linear features to the east are associated with the striations on the Precambrian metamorphic gneisses of the Mozambique Belt. They represent a relic of the original sedimentary structures. Using the standard false colour composite (FCC) the area was broad1y divided into two on the basis of spectral reflectnnce ch~racteristics and texturol pr'ltterns.The cnmbrian metamorphic rocks to the south and east are mainly in the yellow/brown colour hues and the volcnnics to the west are in the blue/green colour hues. A detailed analysis of five selected areas in these broad divisions is made basing the interpretation on a number of measurable and recognizable features on the images including geometric shapes or forms and patterns. The information from the image is field checked and together with collateral data is compiled into Precnmbrian metamorphic rocks to the south and east are mainly in the yellow/brown colour hues and the volcnnics to the west are in the blue/green colour hues. A detailed analysis of five selected areas in these broad divisions is made basing the interpretation on a number of measurable and recognizable features on the images including geometric shapes or forms and patterns. The information from the image is field checked and together with collateral data is compiled into a refined map, a synthesized qeological map of the Nairobi-Kajiado-Machakos arei'l