l>Understanding Topographic Maps

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Understanding Topographic Maps A topographic map, just put, is a two-dimensional representation of a part of the three-dimensional surface ar of the earth. Topography is the shape of the soil surface, and also topographic maps exist to stand for the soil surface. Topographic maps space tools supplied in geologic studies because they display the construction of the earth’s surface. Cartographers deal with the trouble of representing the three-dimensional land surface ar on a level piece of record by using contour lines, thus horizontal distances and vertical elevations have the right to both it is in measured native a topographic map. Basic Information
The terms listed below indicate what details is included on a topographic map, and also where it have the right to be found.

Map Scale: Maps come in a variety of scales, covering locations ranging native the entire earth to a city block (or less).

Vertical scale (contour interval): all maps have a horizontal scale. Topographic maps additionally have a vertical range to allow the decision of a suggest in 3 dimensional space.

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

The following are general characteristics of contour lines:

1. Contour lines carry out not cross each other, divide or split. 2. Carefully spaced contour lines represent steep slopes, conversely, edge lines that room spaced far apart stand for gentle slopes. 3. Contour lines tendency up valleys and form a "V" or a "U" whereby they cross a stream.

On most topographic maps, table of contents contour currently are normally darker and are marked with your elevations. Lighter contour lines carry out not have elevations, but can be established by counting increase or down from the nearest index contour line and multiplying by the edge interval. The contour interval is proclaimed on every topographic map and also is normally located listed below the scale.

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Creating topographic profiles: Remember the topographic maps represent a check out of the see as checked out from above. For producing a in-depth study that a landform it is essential to construct a topographic profile or cross-section v a certain interval. A topographic file is a cross-sectional watch along a line attracted through a section of a topographic map.

A profile may be built quickly and accurately across any straight line on a map by following this procedure:

a. Place a strip of document along a line across the area wherein the profile is to it is in constructed.

You are watching: On topographic maps contour lines that are farther apart indicate

b. Mark on the file the specific place whereby each contour, stream and hill optimal crosses the profile line. c. Brand each mark with the elevation of the edge it represents. d. Prepare a vertical range on profile record by labeling the horizontal lines matching to the elevation of each index edge line. e. Location the file with the labeling contour lines at the bottom of the profile record and project each edge to the horizontal line of the same elevation. f. Affix the points.

Stream Gradient: Stream gradient can likewise be identified from a topographic map. The gradient of a steam or flow is figured out by measure a section of a present or river and also dividing the street (in miles) right into the vertical distinction (in feet) between the two points. The an outcome is express in feet per mile (ft./mi.). The equation provided is:


Tips because that Interpreting Topographic Maps upright exaggeration: vertical exaggeration is the impact that is produced when the horizontal and also vertical scales on her topographic profile room not the same.

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

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Topographic Map example As one example, look at a map the the Sulphur-Boundary Creek area follow me the center Fork that the Salmon river This map is a geologic map that glacial geology in the area, drawn on a topographic map base. The map has a edge interval of forty feet, which means that every place in between the significant 6800 foot line and the following lowest heat (which is 6760 feet, and not marked) has an elevation equal or higher than 6760 feet, however less 보다 6800 feet. Friend can figure out the elevation of any point by detect the nearest labeled line, count the number of lines above or listed below it, multiplying by the edge interval, and adding or individually the result from the nearest marked contour line. The much more closely spaced the edge lines, the steeper the slope. You can discover out precisely how steep the steep of the area you are interested in by individually the lowest elevation indigenous the highest, and also dividing the an outcome by the horizontal distance. Horizontal distance is found on the scale. As you look at the map, notice that the edge lines enclose smaller and smaller areas. The smallest circles stand for the tops of peaks, and some are marked with x’s with numbers next to them. The numbers space the elevation at the peak of the peak.

monitor a contour line follow me its length. Notification the indentations. Together the edge lines overcome gullies or stream drainages, lock "vee" uphill. Drainages that have water in castle year-round have actually solid present connecting the points of the vees. Drainages that have water only part of the year are marked with dashed lines.