a topographic map is used to show topography and features using symbols
TRANSCRIPT
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Topographic Map
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• A topographic map is used to show topography and features using symbols.
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Map Symbols• Green- vegetation• Blue- water• Brown- natural features• Black/red- man made features
• http://pubs.usgs.gov/gip/TopographicMapSymbols/topomapsymbols.pdf
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• Contour lines- indicate elevation using lines and associated numbers
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• Forests and Clearings- shaded green• Streams- shown in blue• Trails- single dashed lines• Roads- red double lines (dashed for dirt, thicker
for major roads)
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• Buildings:• Solid- inhabited (house)• Hollow- uninhabited (barn)• Multiple buildings may be shaded pink
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• Boundaries: Broken lines, shape depends on type. • Benchmarks: indicate survey, uses triangles or X
and BM with elevation measurements.
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• Contour Lines• Each line connects points of equal elevation• Measured in terms of elevation above or below sea level• Can be based on other elevations
• Illustrates shape of land surface on a map• Can indicate which way water flows (from higher
elevations to lower elevations)
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Contour Intervals
• Elevations are evenly spaced vertically for ease of reading• Spacing depends on topography• High relief (mountains) have larger intervals so not too
crowded to read easily
• Intervals are noted in margin of map• Every 5th line is marked darker as an Index
contour and are usually labeled. (usually wider as well)
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Contour Intervals• You can determine contour interval by dividing elevation
difference of index contours by 5.
• Units of elevation are marked in the margin. • Most US maps use feet, but some do use meters.
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Map Scale• Drawn so that distance on map are proportional to
distance on ground. • Scale provides the proportions used
• Verbal Scales state what distance on map equals specific distance on ground• (ex: 1 inch = 2000 feet)
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• Fractional scales do not provide units, provide the ratio of map distance to the equivalent distance on the ground• Written as fractions (1/62,000) or ratios (1:62,000)• Can use any units and be turned into a verbal scale.
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• Bar scales are lines drawn to a known ground length• Provide distance marks for visual estimation• Can be sued like a ruler to measure the distance• Be careful where zero point is located when using the bar
scale.