What do hachures indicate on a topographic map?

hachured contour. [symbology] On a topographic map, concentric contour lines drawn with hachures to indicate a closed depression or basin. Concentric contour lines drawn without hachure marks indicate a hill.

What do hachures represent?

Hachures (/ˈhæʃʊərz/) are an older mode of representing relief. They show orientation of slope, and by their thickness and overall density they provide a general sense of steepness.

Why would a cartographer use hachures?

Hachuring across an area creates tonal variations throughout the map. These tonal variations are a form of analytical hillshading, creating a three-dimensional representation of the topography. Such hillshading can employ vertical or oblique lighting techniques to create such effects.

What does nearness of contour lines indicate?

3-D Surface To achieve this, contour lines are drawn closer or more apart, based on the summits and valleys of the land. Someone who read the diagram needs only to follow the nearness of the contour lines with each another to understand the steepness or flatness of a certain area of the property.

What is every 5th contour line called?

index contour
To make topographic maps easier to read, every fifth contour line is an index contour. The index contour lines are the only ones labeled. The index contours are a darker or wider line in comparison to the regular contour lines. Elevations are marked on the index contour lines only.

How do you read a contour survey?

Widely spaced contour lines indicate gentle slope. Equally spaced contour lines indicate uniform slope. Closed contour lines with higher elevation towards the centre indicate hills. Closed contour lines with reducing levels towards the centre indicate pond or other depression.

What is the difference between a valley and saddle?

If you are in a saddle, you see high ground in two opposite directions and lower ground in the other two directions. Contour lines for a saddle normally resemble an hour glass. Valley – A valley is a stretched-out groove in the land, usually formed by streams or rivers.

How do you know where a river starts?

The place where a river begins is called its source. River sources are also called headwaters. Rivers often get their water from many tributaries, or smaller streams, that join together. The tributary that started the farthest distance from the river’s end would be considered the source, or headwaters.