Topographic Maps and Profiles (Chapter 7)

Datum or Reference Plane

Every topographic map shows, to scale the width, length, and variable height of the land above a datum or reference plane.

Bench Marks

In addition to index contours, bench marks (shown on maps with the symbol X,BM,or "triangle with dot on the middle") are usually present on the map.

Contour interval

In the bottom central margin of every topographic map, the Contour interval is indicated letting the reader know the amount of elevation change that occurs between each contour line.

Topography

"the shape of the land" and refers to the surface configuration of features on the Earth such as hills, valleys, lakes, slopes, streams, ect

Topographic profile

A side view- will provide a more useful representation of the elevation and slopes of an area. A topographic profile is a cross section along a given line which represents an outline of the physical features at the Earth's surface.

Townships

All states were divided into six square mile area called townships, and described by a grid system with reference to established base lines and principal meridians

Topographic Maps

Are important research tools that provide insight into the various processes that the surface of the Earth.

U.S. Geological Survey Standard Colors and Map Symbols (Brown)

Contour lines

Contour Slope

Contour lines that are closely spaced spaced together indicate a steep slope; contour lines widely spaced apart indicate a gentle or gradual slope.

Sections

Each township is divided into 36 one-mile square parcels of land, called sections, with each section containing 640 acres.

Contour Line

Is a line drawn on a topographic map that connects all points that have equal elevation above or below a datum.

U.S. Geological Survey Standard Colors and Map Symbols (Red)

Major roads and highways

Graphic scales

Often refers to as bar scales, are a series of bars divided into segements that show the relation between measurements on the maps to actual distance on Earth.

Datum

Reference plan on the Earth's surface.

Fractional Scales

Sometimes called ratio scales (eg., 1:24,00 or 1:62,500) expresses a distance of one unit on the map represents some distance of the same unit on the surface of the Earth.

Index Contour

To help determine the elevation of the contour lines, on most maps every fifth contour line is printed as a bold line, called index contour. They are labeled with elevation data to help interpret the map

United States Geological Survey

Topographic maps have been produced by the United States Geological Survey (USGS) Since the late 1800's and most areas of the united states have been accurately portrayed on these commercially availible maps.

U.S. Geological Survey Standard Colors and Map Symbols (Green)

Vegetation, woods, orchards, vineyards

U.S. Geological Survey Standard Colors and Map Symbols (Blue)

Water features such as lakes, swamps, rivers, streams; intermittent water features are depicted with a dashed line