Because of the difficulty of making field measurements in snow-covered mountainous regions, remote sensing is attractive as a means of measuring snow-cover properties. For hydrological applications, the primary differences between remote sensing instruments are in their spatial, temporal, spectral, and radiometric resolutions. Optimizing one type of resolution generally involves some sacrifice in other types of resolution, e.g., the Landsat Thematic Mapper (TM) has a much better spatial resolution than the AVHRR (30 m versus 1 km pixel size respectively); however, the AVHRR can provide daily coverage of a given point, whereas the TM can only provide bi-weekly coverage. The possibilities for detecting snowpack properties are largely determined by the wavelength being recorded by the remote sensing instrument. Visible and near infrared wavelengths, because they do not penetrate far into the snowpack, mainly provide information about the surface of the snowpack; however, microwave wavelengths can penetrate the snowpack, thereby providing an opportunity to collect volume integrated data.