Surveying II Module 1

CONTOUR LINE

This line on a map representing an imaginary line

on the land surface, all points of which are having

the same elevation above a datum plane, usually

mean sea level

contour map

also known as an isoline map, is a map illustrated with contour lines, for example a Topographic map, which thus shows valleys and hills, and the steepness or gentleness of slopes.

Contouring

The process of tracing contour lines on the surface of the earth is called

INDEX, INTERMEDIATE, SUPPLEMENTARY

TYPES OF CONTOUR LINES

SUPPLEMENTARY

These contour lines resemble dashes. When drawn, they show changes in elevation of at least one-half the contour interval. ______ lines are normally found where there is very little change in elevation, such as on fairly level terrain.

INTERMEDIATE

➢ The contour lines falling between the index contour lines are called intermediate contour lines. These lines are finer and do not have their elevations listed. There are normally four _____ contour lines between index contour lines.

index

Starting at zero elevation or mean sea level, every fifth contour line is a heavier line. These are known as index contour lines. Normally, each ____ contour line is numbered at some point. This number is the elevation of that line.

UNIFORM (Gentle SLOPE), UNIFORM (STEEP SLOPE), Concave slope, Convex slope,

TYPES OF SLOPE

Convex slope

are widely spaced at the top and closely spaced at the bottom

concave slope

are closely spaced at the top of the terrain feature and widely spaced at the bottom.

UNIFORM (STEEP SLOPE)

are evenly spaced but closer together. The closer the contour lines, the steeper the slope.

UNIFORM (Gentle SLOPE)

are evenly spaced and wide apart.

All points in a contour line have the same elevation.

Flat ground is indicated where the contours are widely separated and steep-slope where they run close together.

A uniform slope is indicated when the contour lines are uniformly spaced and;

A plane surface when they are straight, parallel and equally spaced.

Characteristics of contours

Major Terrain Features

Minor Terrain Features

Supplementary Terrain Features

Terrain features

terrain features

are derived from a complex landmass known as a mountain or ridgeline. The term ridgeline is not interchangeable with the term ridge.

ridgeline

is a line of changes in low to high ground. These changes can encompass a total of 10 natural or man-made terrain features

hill, saddle, valley, ridge, depression,

Major Terrain features

depression

A low point in the ground. They are represented by close contour lines that have thick marks pointing toward low ground.

depression

A series of closed contour lines on the map indicate a ____ if the higher values are outside

ridge

A sloping line of high ground

Ridge

If the higher values are inside the bend or loop in the contour, it indicates a ___.

Valley

If the higher values are outside the bend, it represents a ___.

valley

A stretched-out groove in the land, usually formed by streams or rivers.

saddle

Depressions between summits is called a ___. It is represented by four sets of contours as shown. It represented dip in a ridge or the junction of two ridges. And in the case of a mountain range, it takes the form of a pass.

saddle

A dip or low point between two areas of higher ground.

hill

A series of closed contour lines on the map represent a ___, if the higher values are inside

hill

An areas of high ground. From a hilltop, the ground slopes down in all directions.

draw, spur, cliff

Minor Terrain features

draw

is a stream course that is less developed than a valley.

spur

is a short, continuous sloping line of higher ground normally jutting out from the side of a ridge.

cliff

is a vertical or near-vertical feature that is an abrupt change of the land.

cut, fill

supplementary Terrain features

cut

is a man-made feature resulting from cutting through raised ground, usually to form a level bed for a road or railroad track.

fill

is a man-made feature resulting from filling a low area, usually to form a level bed for a road or railroad track