Topographic Map

• A topographic map is used to show topography and features using symbols.

Map Symbols• Green- vegetation• Blue- water• Brown- natural features• Black/red- man made features

• http://pubs.usgs.gov/gip/TopographicMapSymbols/topomapsymbols.pdf

• Contour lines- indicate elevation using lines and associated numbers

• Forests and Clearings- shaded green• Streams- shown in blue• Trails- single dashed lines• Roads- red double lines (dashed for dirt, thicker

for major roads)

• Buildings:• Solid- inhabited (house)• Hollow- uninhabited (barn)• Multiple buildings may be shaded pink

• Boundaries: Broken lines, shape depends on type. • Benchmarks: indicate survey, uses triangles or X

and BM with elevation measurements.

• 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)

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)

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.

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)

• 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.

• 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.