Topographic Mapping Questions and Answers

Answer: C

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason is the constraint. Contour spacing on the paper is the vertical interval divided by the slope and then reduced by the scale, so steep ground at small scale crowds the lines together. A fine interval would produce a solid band of ink conveying nothing, so the interval is opened out until the lines separate - accepting less detail in exchange for a legible sheet.

Answer: D

Correct answer: form lines

Form lines are sketched to convey the shape of the ground where no levelling has been done, so they are drawn broken to warn that they carry no reliable height. Index contours are the thickened, labelled lines drawn every fifth interval; supplementary contours are extra lines at half the interval on flat ground; and depression contours carry hachures pointing inward.

Answer: A

Emphasising every fifth line and labelling it lets a reader establish a height quickly and then count the thin lines from there. The device costs nothing in ink and greatly speeds up interpretation, which is why every published series uses it.

Answer: B

A benchmark is physically fixed, usually cut into a wall or set in a pillar, so a surveyor can return to it and recover the height. A spot height is a value printed on the map with no permanent mark on the ground at all, so it cannot be reoccupied.

Answer: C

Each national survey adopts a datum derived from tide-gauge observations at one or more stations. Two countries with different datums can assign slightly different heights to the same summit, which matters in border regions.

Answer: D

Each survey works from its own sea-level datum, and the datums differ by up to a couple of metres. The discrepancy is not an error by either survey but a consequence of the reference each has chosen, and it shows up wherever two national series meet at a border.

Answer: A

Correct answer: 1 and 2 only

Statements 1 and 2 are correct: contours at different heights cannot cross, since a point cannot have two heights, and the exception is the overhang or vertical cliff where they touch or merge; and even spacing does mean uniform slope. Statement 3 is wrong - the interval is chosen for the scale and the relief of each sheet, so a mountain sheet and a fenland sheet in the same series routinely differ.

Answer: B

Steepening upwards is the signature of a concave slope, which appears hollowed when seen from the side. The convex case reverses the pattern, with the close spacing at the bottom and the slope easing as it rises, and it appears rounded from the side.

Answer: C

Correct answer: closely spaced contours on one side and widely on the other

An escarpment is asymmetric by definition: a steep scarp face on one side and a gentle dip slope on the other. The contour pattern reproduces that asymmetry directly, crowding on the scarp and opening out on the dip. Closed contours with inward hachures are a depression, and an hourglass is a col.

Answer: D

The vertical scale is 1:10,000 once expressed as a ratio, and dividing the horizontal denominator of 50,000 by that gives 5. Both scales must be written as ratios before they can be compared, which is the step that trips people up here.