The interpretation of radar sounding data from Mars where significant topographic relief occurs will require echo source discrimination to avoid the misinterpretation of surface echoes as arising from the subsurface. This can be accomplished through the identification of all radar returns from the surface in order to positively identify subsurface echoes. We have developed general techniques for this using airborne radar data from the Dry Valleys of Antarctica. These data were collected in a single pass, including Taylor Glacier, ice-covered Lake Bonney, and an ice-free area of Taylor Valley. The pulsed radar (52.5--67.5 MHz) was coherently recorded. Our echo discrimination techniques included a radar simulator using a digital elevation model (DEM) to predict the location and shape of surface echoes in the radar data. Real and simulated echo strengths were used to calculate a signal-to-clutter ratio. This was complemented by the cross-track migration of radar echoes onto the surface. These migrated echoes were superimposed on the DEM and imagery in order to correlate with surface features. Using these techniques enabled us to identify a number of echoes in the radar data as arising from the surface and to identify subsurface echoes, including a continuous reflector under the main trunk of Taylor Glacier and multiple reflectors beneath the terminus of Taylor Glacier. Surface-based radar confirms the thickness of the glacier at three crossing points. The results illustrate the importance of using complementary techniques, the usefulness of a DEM, and the limitations of single-pass radar sounding data.