State whether the following is true or false.
Every topographic map states the vertical interval of its contours.
Answer: C
Without it the lines are only a pattern, since counting them yields no height change. The interval belongs with the scale and the datum among the facts a sheet must declare for its content to be usable at all, and it is stated in the margin alongside them.
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The chief advantage of a contour over hill shading is that a contour
Answer: D
A labelled line states a value, which shading never does. Shading is in fact the more vivid of the two, which is why published sheets frequently carry both and let each do the thing it does best, shading for the shape and contours for the numbers.
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Consider the following statements about reading relief.
1. A V in the contours pointing uphill indicates a valley.
2. A saddle appears as an hourglass pattern of contours.
3. Closed contours always indicate a summit.
Answer: A
The first two are correct. The third ignores the hachured depression contour, which is also a closed loop but encloses ground falling inwards rather than rising. The inward ticks are the only thing that separates a crater from a hilltop on the sheet.
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Terrain drawn on a modern topographic sheet is most often derived from
Answer: B
Contours are now generated from a gridded or point-cloud model and then edited for cartographic quality. The older field methods survive mainly in the historical sheets they produced, and in the occasional survey of ground no aircraft or satellite can usefully see.
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Assertion (A): Contours generated automatically from an elevation model are usually edited before publication.
Reason (R): An unedited line can wander in a way that no real slope does.
Answer: C
Both are true and the reason gives the cause: noise in the model produces small kinks and loops that would be read as landforms, so the lines are smoothed and tidied without moving them away from the heights they represent.
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