Topographic Maps
Topography: The surface features of the Earth; the rises and falls of the land
Topographic Maps
 Show 3-D surface on a 2-D plane
 Made on Quadrangles (7.5 minute or 15 minute squares of latitude and
longitude)
 Made by the USGS for military, scientific, and commercial use
Features
 Name and Date
o Shown in the lower right
o Usually named after nearby towns
 North Arrows
o Located just left of center in the bottom margin
o MN – Magnetic north (where a compass points)
o GN – Grid north (north for the US grid system – townships and
ranges)
o N↑ – True north (points to the north pole)
 Latitude and Longitude
o Listed at the map sides and corners in degrees minutes and seconds
 Scale
o
o
o
o
Located at the bottom center
Verbal - A statement (one inch equals one mile)
Graphic - Shows actual distances
Fractional
 States a ratio or fraction of measurements
 Example: 1:24000 => one unit on the map = 24000 units on
the earth
 Smaller scales show more area, but less detail (things on the
map appear smaller)
 Larger scales show less area, but more detail (things on the
map appear larger)
 Symbols
o Buildings, Schools, Railroads, Churches
o Colors
 Red and Black - roads and man-made features
 Purple - revised features
 Blue - water features (lakes, streams, marshes)
 Brown - contour lines
Contour Lines
 Represent elevation above sea level and shape of the land
 Connect and mark points of elevation
 Contour interval - difference in elevation between 2 contour lines
 Benchmarks
o Show points of exact elevation
o Examples: BM 106; VABM 1212; X 5487; BM X 236
 Relief - difference in elevation between 2 points
 Slope = relief / distance
Contour Line Rules
 Contour lines may never cross.
 Hills - Contour lines form closed concentric circles
 Depressions - Contour lines form closed concentric circles with hachure
marks pointing inward
 Steep slopes - contour lines are close together
 Gentle slopes - contour lines are widely spaced
 Rule of V's - In streams and stream valleys, the contour lines bend and
make a 'V' pointing upstream.