Map, Compass & GPS

Map, Compass & GPS
Wild flowers along Fall Creek on the way to the Green Lakes - Oregon

Monday, March 9, 2015

Topographic Map Symbols

Colors and symbols add the detail unique to a topographic map.  These details may not be found in gazetteers or travel guides.  Map detail includes important information about elevation, water, structures, trails, ground cover and roads; and much more.

 “The mapmaker has been forced to use symbols to represent the natural and man-made features of the earth’s surface.  These symbols resemble, as closely as possible, the actual features themselves as viewed from above.”

                                                                        U.S. Army Field Manual FM 21-28                                                                                                     Map Reading and Land Navigation, 1993

Topographic maps are rich in symbols.  Specific to a location, symbols identify features such as buildings, springs, bench marks, mines and bridges.  The United States Geologic Survey’s (USGS) guide Topographic Map Symbols is four pages long and lists dozens of symbols.  To view the USGS’s complete listing go here.

The following graphics are a sampling from Topographic Map Symbols.  The symbols below are those used for rivers, lakes and canals.  Note the different colors used.
The graphic below illustrates symbols related to buildings and other man-made features.

Note that the color of these symbols is predominantly black.

Let’s highlight a few symbols that the backcountry hiker will find helpful (the symbol will be listed to the left.)

 Bench Marks are survey monuments.  Location and elevation data is accurate.   Bench Mark will be represented by the letters BM and next to it will be printed the elevation data; see map above.  In the backcountry, Bench Marks will have a brass/bronze plate at the location to identify the mark and its position data.  Please do not tamper with a Bench Mark.

A trail is highlighted in the map above.  Trails are black dashed lines.

     Useful to the hiker are four wheel drive roads (4WD) and unimproved roads.  These are commonly called jeep roads and may be usable on foot, horseback or mountain bike.  Some of these roads may not be passable by vehicle.           

Thin, powder-blue lines represent streams.  What looks like a dashed blue line (right half) represents an intermittent stream; a flow that may disappear in dry weather.

I recommend spending some time browsing through Topographic Map Symbols and to become familiar with the symbols listed. The web site provides a fine review of colors and symbols that are linked to photographs.

No comments:

Post a Comment