Low altitude stereo-paired aerial photographs are often used in which of the following types of investigations?

• A. Mapping soil types
• B. Site histories
• C. Landslide and fault analyses
• D. Wetland delineation

Answer: (C)

Three-dimensional viewing of the ground is the key idea here. When photographs are taken at low altitude, the scale is large and the resolution is high, so fine surface details are visible. A stereo pair lets you view the same area from two slightly different angles, which creates parallax and allows a photogrammetrist to reconstruct elevations and 3D shapes of the terrain. That 3D perspective makes it much easier to spot subtle ground features that indicate movement or structural discontinuities—things like landslide scarps, displaced blocks, toe and crown lines, tension cracks, and fault traces.

Because landslide and fault features produce clear surface expressions in three dimensions, low-altitude stereo imagery is especially well suited for identifying and characterizing these phenomena, mapping their extent, and interpreting their kinematics. Soil type mapping, site histories, and wetland delineation rely more on surface materials, vegetation, moisture, and historical records, which aren't as directly revealed by 3D topography alone, so the stereo approach at low altitude is not as directly advantageous for those purposes.