Digital Cartography and Automation Questions and Answers

Answer: A

Each feature is stored by its geometry and its attributes, so a road is a sequence of coordinates rather than a set of coloured cells. This keeps boundaries sharp at any scale of display, since the geometry is redrawn rather than magnified.

Answer: B

Every cell covers a fixed patch of ground and carries one value, which suits continuous phenomena such as elevation or reflectance. Sharp boundaries become stepped, since a cell cannot be partly one thing and partly another.

Answer: C

Correct answer: raster

A continuous surface has a value everywhere, and a raster stores exactly that - one value per cell over the whole extent. Vector data suit discrete objects with definite boundaries: a road, a parcel, a building. Rainfall has no boundaries of its own, so forcing it into polygons would invent them.

Answer: D

Correct answer: False

A raster has a fixed cell size, so enlarging it beyond that resolution merely makes the cells visible as blocks - no detail appears that was not recorded. Vector geometry is stored as coordinates and can be drawn at any scale sharply, though that sharpness says nothing about whether the data were accurate enough to warrant it.

Answer: A

Connectivity, adjacency and containment are stored explicitly, so the software knows that two districts share a boundary rather than merely having lines that happen to coincide. This is what makes network and overlay analysis possible.

Answer: B

Each line is an independent string of coordinates, and shared boundaries are digitised twice with no record that they are the same edge. Simple to produce, but it makes adjacency queries impossible without rebuilding the relationships.

Answer: C

Correct answer: two versions of the same boundary are overlaid

Where the same line has been digitised twice, or captured from two sources, the two versions differ by a small amount along their length. Overlaying them creates a chain of long thin polygons between the two. They are geometrically valid and analytically meaningless, and they are removed by a tolerance or by snapping the boundaries together first.

Answer: D

Correct answer: forcing nearby vertices to a common position

Snapping pulls a vertex within a stated tolerance onto an existing one, so that lines meant to meet actually share a point rather than merely appearing to. Without it a digitised network is full of tiny gaps and overshoots, invisible on screen and fatal to any analysis that depends on connectivity.

Answer: A

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

Both are true and the reason gives the mechanism. A routing algorithm follows shared nodes, so two line ends a few centimetres apart are not connected however close they look at map scale. The network appears complete and the route fails, which is why connectivity must be validated rather than inspected.

Answer: B

It keeps the points that matter most to the shape and discards those within a stated tolerance of the line between them. Raising the tolerance removes more vertices, which is how the same data serve several display scales.