MappingMapping

Chapter 16Chapter 16

Uses of Topographic Maps

To determine the topography or relief of a tract of land.

To determine hydrologic features such as drainage basins, streams, rivers and bodies of water.

To determine the cultural features or man-made features such as highways, railroads, dams and buildings.

Topographic maps are used by engineers and architects to determine building layouts, utility connections and drainage requirements. Contractors use topographic information to determine earthwork requirements.

Methods of Collecting Topographic Data

Satellite Imagery

Aerial Photography

Existing Topographic Maps

Field Work

Total Station

GPS

Control for Topographic Surveys

Horizontal Control: Establish Traverse.

Vertical Control: Establish Elevations from Benchmark.

ContoursContours

Used to Determine Topography

Contours

Contour lines are lines of equal elevation.

The contour interval is defined as the difference in elevation between contours.

Rules for Drawing Contours

Contour lines must close upon themselves. They cannot simply dead-end.

Contours are perpendicular to the direction of slope.

The slope between contour lines is assumed to be uniform.In other words, contour lines are assumed to be man-made.

The distance between contours indicates the steepness of the slope.

Concentric closed contours represent hills or depressions.

Examples of Rules Regarding Contours