Contours Lecture Notes

Flashcards about facts and definitions of contours

Contour Lines

Imaginary lines that do not actually occur on the ground, shown by brown lines on a 1:50 000 map.

Contour Lines Intersection

Contours cannot intersect (cross) each other and are continuous and closed except when they run to the edge of a map.

Contour Numbers

Numbers on contours are printed the right way up, upside down, or sideways to indicate which contour lines are higher or lower.

Slope Indication

When contour lines are close together, the slope is steep; when they are far apart, the slope is gentle.

Index Contours

Certain contours are printed in bold to help calculate altitude ranges quickly; they are 100m apart on a 1:50 000 map and 20m apart on a 1:10 000 orthophoto map.

Contour interval

The difference in altitude between successive contours.

Subcontours

In very flat regions, fine, broken, brown lines used to show relief features where a 20m contour interval is too large.

Uniform Slope

A slope that is the same throughout, also called an even slope, with contour lines at more or less equal distances apart.

Gradual Slope

Also called a gentle slope, with contour lines far apart, and the altitude varies little over a great distance.

Steep Slope

Contour lines are very close together, and the variation in altitude is great over short distances.

Terraced Slope

Also called a stepped slope, where the slope is alternately steep then gentle, with some contours close together and others further apart.

Convex Slope

The bottom of the slope is steep, becoming more gentle towards the top, forming an outward curve; contour lines are closer together at the bottom and further apart as one moves up.

Concave Slope

The reverse of a convex slope, forming an inward curve; contours are spaced far apart at lower altitudes and close together at higher altitudes.

Vertical Slope

Also called a cliff, identified by overlapping contours.

Spurs

Low mountain ridges often divided by incised valleys, recognized when the contours form a “V” shape, and the base of the “V” points towards lower ground.

Valleys

Recognized when the “V” shape of the contours points to higher ground.

Watershed

Also known as a divide, it is a ridge or higher ground that separates two river systems or drainage basins.