Topographic Surveying and Mapping
Core concepts
Topographic surveys locate natural and cultural features and depict relief. Candidates must know contour intervals, contour characteristics (they never cross except at overhangs), spot elevations, and the difference between planimetric and topographic maps. Field methods include total station and GNSS, and deliverables include digital terrain models and plan sheets.
Traps
Questions frequently test contour interpretation: closely spaced contours indicate steep slopes; contours crossing a stream form a V pointing upstream. Another trap is confusing contour interval (vertical distance between contours) with horizontal spacing. Also watch for scale questions-a 1:2,400 scale means 1 inch equals 200 feet, and map accuracy depends on scale.
Worked example
If contours are at 2-foot intervals and a point lies halfway between the 620 and 622 contours on a uniform slope, its elevation is approximately 621 feet.
Rule of thumb
Contours point upstream in valleys, and spacing indicates slope steepness, not elevation.