Which surveys determine location, structural type, total length, and span-length ratio by mapping topography and geology?

• A. Geotechnical surveys
• B. Seismic surveys
• C. Hydrotechnical surveys
• D. Topographic and geologic surveys

Answer: (D)

Mapping topography and geology provides the spatial framework and subsurface conditions needed to decide where a structure goes, what form it should take, and how long it will be. Topographic surveys capture elevations, contours, terrain features, slopes, and access routes, which determine feasible alignments and overall length. Geologic surveys identify soil and rock types, fault locations, and groundwater conditions, guiding the choice of structural system and foundations, and setting practical limits on span lengths. Together, these maps allow you to determine location, the most suitable structural type given ground conditions, the total project length, and how spans should be arranged to fit the terrain. The other survey types focus more narrowly on soil properties, seismic imaging, or hydraulic aspects and do not by themselves provide the comprehensive topographic-geologic framework needed for siting and layout.