Multispectral satellite imagery and other remote sensing techniques may now be employed to carry out surveys over large land areas so that fuller use can be made of locally available materials in order to reduce the costs of road construction. In many developing countries local resources are often not used as extensively as would be possible, due to the adaptation of specifications for road building materials that have been derived in industrialized countries with temperate climates and different geology.

These specifications are often inappropriate for natural gravels, weathered rock, and concretionary materials found in the tropics, many of which can be used successfully for constructing lightly-trafficked roads. The value of using recent technological developments in remote sensing methods and techniques of image analysis to locate and map the occurrence of such indigenous engineering materials are discussed with reference to a survey undertaken in Botswana to locate calcrete for low-cost road construction in the Kalahari Desert.

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