A topographic map series is normally revised
Answer: A
Roads, buildings and boundaries alter far faster than the relief, so revision concentrates on them and the contours may stand for decades. This is why a sheet's revision date matters more than its original survey date.
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Assertion (A): The contour information on an old topographic sheet may still be reliable even where the roads shown have vanished.
Reason (R): Relief changes far more slowly than the works of people built upon it.
Answer: B
Both are true and the reason explains the assertion: hillsides endure while roads are rerouted and settlements grow, so the two kinds of content on a single sheet age at quite different rates and must be trusted to quite different degrees.
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Consider the following statements about topographic survey.
1. A benchmark can be reoccupied by a later surveyor.
2. Triangulation fixes horizontal position from observed angles.
3. Levelling determines the bearing of a line from north.
Answer: C
The first two are correct. The third misstates levelling, which yields height differences; bearings are obtained with a theodolite or a compass and belong to a different operation entirely, which is why the three are treated as separate survey tasks.
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Hachures, as used on older topographic maps, indicate slope by
Answer: D
Correct answer: short lines drawn down the direction of fall
Hachures are drawn along the line of steepest descent, and slope is read from their weight and spacing: short, thick, closely set strokes for steep ground and fine, widely spaced ones for gentle. They convey the shape of the land well but carry no heights, which is why contours displaced them - hachures survive today only for depressions and for cuttings and embankments.
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State whether the following is true or false.
Contours replaced hachures on topographic maps because contours can be measured.
Answer: A
A hachured slope shows the shape of the land but yields no height at any point, while a contour states one exactly. Once heights were wanted for engineering and artillery, the measurable representation displaced the pictorial one.
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A topographic map differs from a thematic map principally in that it
Answer: B
Correct answer: shows many kinds of feature together
A topographic map is general purpose: relief, drainage, settlement, communications, vegetation and boundaries all appear on one sheet, and the reader chooses what to take from it. A thematic map selects one subject and subordinates everything else to showing its distribution. Publisher and scale do not enter into it, and thematic maps frequently carry relief on their base.
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A re-entrant, in relief interpretation, is
Answer: C
It is the low ground between two spurs, and its contours V towards the higher ground in the usual way for a valley. The spur is its counterpart, the projecting high ground lying between two re-entrants, and its contours V the other way about.
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State whether the following is true or false.
A plateau appears on a contour map as a wide area with few contours surrounded by many closely spaced ones.
Answer: D
The flat top needs almost no lines because the height barely changes, while the steep edges crowd them together into a dense band. The pattern is distinctive enough to be recognised at a glance once it is known, and it distinguishes a plateau from a rounded hill immediately.
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A map has a contour interval of 10 m. Between two adjacent index contours labelled 100 m and 150 m, how many thin contours are drawn?
Answer: A
The lines at 110, 120, 130 and 140 metres lie between them, which is four. The two labelled lines themselves are the index contours and are not counted among the thin ones, which is the distinction that makes the answer four rather than six.
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Which feature would be shown by a symbol rather than by contours alone?
Answer: B
Contours at a vertical face would coincide exactly, which the drawing cannot show, so a rock symbol is used instead, together with a spot height at the top and bottom. The other three are ordinary slopes that contours describe perfectly well on their own.
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