Agriculture Reference
In-Depth Information
Contours make it possible for the user of a USGS quad map to deter-
mine the height of mountains, depths of the ocean bottom (bathymetric
maps), and steepness of slopes. A topographic map shows more than
contours. The elevations of tops of mountains are often shown, eleva-
tions of ponds or borrow sites, and of key cultural features of interest.
A USGS map includes symbols that represent such features as streets,
buildings and other structures, infrastructure (power and pipelines),
streams, vegetation, and other made-made and natural features.
the information contained in
topoGraphic mapS
If you like reading maps and have experience doing so, you may find
that with little to no instructions you will be able to understand most
of the graphic content shown on a topographic map. For the most part,
interpreting the lines, areas, and other symbols will be easy. The system
of colors and line weights used will also help make the features repre-
sented more obvious. For example, areas shaded in green indicate the
presence of vegetation, usually forest. Features colored in blue represent
water, lines of blue represent small streams, and amorphous shapes can
be lakes and ponds. You will easily understand what you are looking at,
and if not, refer to the legend when in doubt. The various map features
are shown as points, lines, shading, and text. The width of lines and
intensity of colors graphically help to distinguish between higher and
lower levels of importance, depending on the size and extent of the fea-
ture. For example, individual houses may be shown as small, uniform
black squares, while the actual shapes of larger buildings are shown. In
densely built-up areas, most individual buildings are omitted, and the
area is shaded in light gray or perhaps standard urban land use colors.
On some maps major public buildings such as post offices, churches, city
halls, and other landmark buildings are outlined using a set of symbols
that can be found in the legend. Features such as cemeteries, airports,
and athletic facilities also follow a standard set of symbols.
