Abstract. Strategies and techniques for the use of airborne digital image data equivalent to the Landsat Thematic Mapper (TM) and from the NASA Thermal Infrared Multispectral Scanner (TIMS) in geological mapping are discussed. The test areas are in complex Archaean greenstone terrain that has been subject to deep lateritic weathering and subsequent incision. These are spectrally unlike areas that have been covered before, and the analysis is based on new reflected and emitted spectra of natural surfaces. The newly available Landsat TM data over most of Western Australia is seen to have unprecedented potential as an aid to geological mapping in such intractible terrains because of the consistent and clear discrimination of weathered rock surfaces and colluvial soils over a wide range of rock types, particularly in decorrelation stretched three-band and band ratio images. The discrimination is due to the fortuitous association of mixtures of weathering products rather than to the primary mineralogy of the rocks. TIMS data are less useful in bedrock mapping, but offer considerable advantages for mapping the distribution of different types of superficial cover.