Use of Landsat MSS and TM imagery to improve reconnaissance geologic mapping in the Ruby quadrangle, west-central Alaska: A section in Geological studies in Alaska by the U.S. Geological Survey, 1999

By using Multispectral Scanner (MSS) and Thematic Mapper (TM) satellite images, the spatial relation of units JMtu (mafic, ultramafic, and sedimentary rocks, undivided) and PzZrqs (pelitic and quartzitic schist) of Wilson and others (1998) from the northeastern portion of the Ruby 1:250,000-scale quadrangle geologic map was further defined. The MSS image was first analyzed using spectral signatures to separate and highlight pixels associated only with the units of interest. This approach was ineffective at separating the units from areas of the image with similar spectral signatures, but it did show that unit JMtu and associated areas consistently had a high brightness value, while unit PzZrqs and associated areas consistently had a low brightness value. Consequently, a new approach was developed using spectral enhancement to emphasize the differences between these high- and low- brightness areas. Once the TM image was obtained, the spectral signature separation and spectral enhancement approaches were again tested, but the results were similar to those found using the MSS image. By using the results from the spectral enhancement of the MSS image in combination with current ground-truth data, the locations of units JMtu and PzZrqs in the Ruby quadrangle were reinterpreted.