l>Understanding Topographic Maps

Understanding Topographic Maps A topographic map, merely put, is a two-dimensional representation of a portion of the three-dimensional surface of the earth. Topography is the form of the floor surface, and topographic maps exist to stand for the land surface. Topographic maps room tools offered in geologic studies because they show the configuration of the earth’s surface. Cartographers solve the problem of representing the three-dimensional land surface ar on a flat piece of file by using contour lines, therefore horizontal distances and also vertical elevations deserve to both it is in measured from a topographic map. Basic Information
The terms listed below indicate what information is included on a topographic map, and where it have the right to be found.

Map Scale: Maps come in a selection of scales, covering areas ranging indigenous the entire planet to a city block (or less).

Vertical scale (contour interval): all maps have a horizontal scale. Topographic maps likewise have a vertical scale to allow the decision of a point in three dimensional space.

Contour Lines: contour lines are offered to identify elevations and are currently on a map the are developed from connecting point out of same elevation (elevation refers to elevation in feet, or meters, over sea level).

The following are general attributes of edge lines:

1. Contour lines perform not cross every other, division or split. 2. Very closely spaced edge lines represent steep slopes, conversely, edge lines that space spaced far apart represent gentle slopes. 3. Edge lines trend up valleys and form a "V" or a "U" wherein they cross a stream.

On most topographic maps, table of contents contour lines are generally darker and are significant with their elevations. Lighter edge lines perform not have elevations, yet can be determined by counting up or down from the nearest index contour line and multiplying by the edge interval. The edge interval is declared on every topographic map and is generally located below the scale.

Creating topographic profiles: Remember that topographic maps stand for a watch of the see as viewed from above. For creating a thorough study of a landform the is important to build a topographic file or cross-section with a specific interval. A topographic profile is a cross-sectional view along a line drawn through a section of a topographic map.

A profile may be constructed quickly and also accurately throughout any straight line on a map by adhering to this procedure:

a. Lay a strip of document along a line throughout the area where the file is to be constructed.

You are watching: On a topographic map, contour lines that are farther apart indicate

b. Note on the record the precise place whereby each contour, stream and also hill peak crosses the file line. c. Brand each mark with the elevation of the edge it represents. d. Prepare a vertical scale on profile record by labeling the horizontal lines matching to the elevation of every index contour line. e. Ar the document with the labeled contour lines in ~ the bottom of the profile paper and job each contour to the horizontal heat of the very same elevation. f. Affix the points.

Stream Gradient: Stream gradient can also be determined from a topographic map. The gradient that a heavy steam or river is determined by measuring a section of a stream or river and dividing the distance (in miles) right into the vertical difference (in feet) in between the 2 points. The an outcome is to express in feet every mile (ft./mi.). The equation provided is:

Tips for Interpreting Topographic Maps vertical exaggeration: vertical exaggeration is the impact that is produced when the horizontal and vertical scale on your topographic profile are not the same.

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Determining hillslope: among other things, a topographic map can be used to measure the average slope that a hill (or hills).

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Topographic Map instance As an example, look at a map that the Sulphur-Boundary Creek area along the middle Fork the the Salmon flow This map is a geologic map that glacial geology in the area, attracted on a topographic map base. The map has actually a contour interval of forty feet, which means that every place in between the marked 6800 foot line and also the following lowest heat (which is 6760 feet, and not marked) has actually an elevation same or better than 6760 feet, but less 보다 6800 feet. Friend can number out the key of any point by recognize the nearest labeling line, count the number of lines over or below it, multiply by the contour interval, and adding or subtracting the result from the nearest significant contour line. The an ext closely spaced the edge lines, the steeper the slope. You can find out exactly how steep the slope of the area you room interested in by individually the lowest elevation native the highest, and dividing the result by the horizontal distance. Horizontal distance is found on the scale. As you look in ~ the map, notification that the contour lines enclose smaller and smaller areas. The the smallest circles represent the top of peaks, and some are marked with x’s through numbers next to them. The numbers space the elevation at the top of the peak.

monitor a contour line along its length. Notification the indentations. Together the edge lines cross gullies or stream drainages, castle "vee" uphill. Drainages that have water in castle year-round have solid currently connecting the point out of the vees. Drainages that have water only part of the year are significant with dashed lines.