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Topographic Survey 􀁝. Topography - defined as the shape or configuration or relief or three–dimensional quality of a surface Topography maps are very useful for engineers when planning and locating a structure. Topographic Survey. Introduction U.S. Geological Survey (USGS) has developed

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Topographic survey
Topographic Survey􀁝

  • Topography - defined as theshape or configuration orrelief or three–dimensionalquality of a surface

  • Topography maps are veryuseful for engineers whenplanning and locating astructure

Topographic survey1
Topographic Survey


U.S. Geological Survey

(USGS) has developed

maps for a large part of

the US

Napoleon Bonaparte

received his first promotion

because of ability to make

and use maps

Topographic survey2
Topographic Survey


The most common method of representing the

topography of an area is to use contour lines

A contour line is an

imaginary level line

that connects points

of equal elevation

Topographic survey3
Topographic Survey

There are several rules to note when viewing topographic maps:

The rule of Vs: sharp-pointed V usually are in stream valleys,

with the drainage channel passing through the point of the V,

with the V pointing upstream.

The rule of Os: closed loops are normally uphill on the inside and

downhill on the outside, and the innermost loop is the highest


Spacing of contours: close contours indicate a steep slope;

distant contours a shallow slope. Two or more contour lines

merging indicates a cliff.


Contours that point up hill can indicate a valley or stream


Imagine a hill that

has its top sliced off

with a really big knife


When is the steepest part of this terrain?

The shallowest part?

Topographic survey4
Topographic Survey

The selection of the contour is important

The contour interval should be small enough to give the desired topographic detail while remaining economic

Usually every fifth contour line is shown in a heavy, wider line, this is called a index line


The relief is the distance between the highest point and lowest point of elevation on the map.

A mapmaker chooses the contour interval based on the relief.

A smaller interval may be used on a flat map whereas an interval of 100 feet may be used on steep mountainous terrain.

Reading a topographic map
Reading a Topographic Map

  • Topographic maps, like other maps, use symbols to represent part of the Earth’s surface.

  • Different colors are also used to determine different parts of the Earth’s surface:

  • Buildings, roads, railroads and bridges are black.

  • Contour lines are brown.

  • Major highways red.

  • Cities and towns are pink.

  • Bodies of water such as lakes, rivers, ponds and oceans are blue.

  • Wooded areas are represented by the color green

Contour lines the golden rules
Contour Lines: The Golden Rules

  • The following four rules can help you interpret the sizes and shapes of landforms on a topographic map.

  • 1. Contour lines never cross.

  • 2. The spacing of contour lines depends on slope characteristics.

  • 3. Contour lines that cross a valley or stream are V-shaped.

  • 4. Contour lines form closed circles around the tops of hills, mountains, and depressions.