Training On Demand

A topographical map is a representation of the Earth, or part of it.

The distinctive characteristic of a topographic map is that the shape of the Earth's surface is shown by contour lines.  

Contours are imaginary lines that join points of equal elevation on the surface of the land above or below a reference surface such as mean sea level. 

Contours make it possible to measure the height of mountains, depths of the ocean bottom, and steepness of slopes.

A topographic map shows more than contours.   Maps includes symbols that represent such features

as streets, buildings, streams, and woods.  These symbols are constantly refined to better relate

to the features they represent.A topographic map tells you where things are and

how to get to them.In our case, they assist with the location and

verification of wildland fires.They show the distance between any two places,

and they also show the direction from one point to another.

Maps are made to scale; that is, there is a direct relationship, between a unit of measurement on the map and the actual distance on the ground.

If 1 inch on the map represents 1 mile (which converts to 63,360 inches) on the ground, the map's scale is 1:63,360.

A convenient way of representing map distance is by the use of a graphic scale bar.  Most USGS topographic maps have scale bars in

the map margin that represents distances on the map in miles, feet, and kilometers. 

Scale indicates 1:24oooMap is complete with scale bar to measure

distanceContour interval as indicated is 40 ft.

Contour lines are a method of depicting the 3-dimensional character of the terrain on a 2-dimensional map.

Contour are lines drawn on the map represent equal points of height above sea level.

On multi-colored maps, contour lines are generally represented in brown. The map legend will indicate the contour interval—

the distance in feet (meters, etc.) between each contour line.

There will be heavier contour lines every 4th> or 5th contour line that are labeled with the elevation

Contour maps give us the grounds topography by the way the lines interact with each other as seen here.

Other General Map References

Black - man-made itemsBlue - waterBrown - contour linesGreen - substantial vegetationWhite - little or no vegetation Red - major highwaysPurple - features added to the map since the original survey.

Topo maps are used for two main purposes in the fire service:

Triangulate the location/ boundaries of a fireOr

Identify the location of fire resources in the field

Both operations require the use a way to gauge locationLatitude/Longitude or the Public Land Survey System

defines locations on a mapBoth require useful knowledge of compass

operation.

The Public Land Survey System (PLSS) is a way of subdividing and describing land in the United States.

All lands in the public domain are subject to subdivision by this rectangular system of surveys, which is regulated by the U.S. Department of the Interior

The PLSS is used to divide public domain lands, which are lands owned by the Federal government for the benefit of the citizens of the United States.

The original public domain included the land ceded to the Federal Government by the thirteen original States,

It encompasses major portions of the land area of 30 southern and western States.

Since the original PLSS surveys were completed, much of the land that was originally part of the public domain has been transferred to private ownership. 

Alabama Alaska Arizona Arkansas California Colorado Florida Idaho Illinois Indiana Iowa Kansas Louisiana

• Michigan• Minnesota• Mississippi• Missouri• Montana• Nebraska• Nevada• New Mexico• North Dakota• Oklahoma• Ohio• Oregon• South Dakota

• Utah• Washington• Wisconsin• Wyoming

Land is divided into 6-mile-square townships, which is the level of information included in the National Atlas.

Townships are subdivided into 36 one-mile- square sections. Sections can be further subdivided into quarter sections, quarter-quarter sections, or irregular government lots.

Most PLSS surveys begin at an initial point, and townships are surveyed north, south, east, and west from that point.

This line is perpendicular to the Principal Meridian.

Township N SRange E WEach 6 miles squaresFire in T3N R2E

1 mile square640 acresNumbered within Township/Range

½ Sections, ¼ Sections divide the section number further

Identified by cardinal direction location

Ie. “SW ¼ of Section 10”.

Fires are now most often located by Latitudinal and Longitudinal coordinates

Devices utilizing satellites easily gather coordinates for easy referenceDevices must be set to DATUM NAD83 to

provide to correct information PLSS acts as a secondary way of indicating

the location of a wildland fire.PLSS will make conversion to Latitude and

Longitude easy By identifying a fire’s location it can be

determined who must be notified

Triangulation has become a generic term for the process of measuring to two or more known points to determine - using geometry - the location of an unknown point.

To map a fire, firefighters should always triangulate to insure the most accurate possible idea.

Align the base plate with an imaginary line between two points on the map.

Turn the compass dial until the north lines align with the north lines on the map.

Read the bearing set on the compass dial.

Hold the compass flat.Sight from an object

you can identify on the map

Move the dial to match northRemember to account

for magnetic declination

Read and document the bearing

Move to your next landmark

Grid NorthWhere the grid on your map is pointing. Since grid

lines on the map are all parallel, they never meet in one point.

Magnetic NorthWhere the magnetic needle points. These wavy lines

depend on iron magma in the earth that changes each year

According to the NOAA Frisco CO has a 9⁰ E Magnetic Declination in 2012 9°E means we rotate the base plate's orienting arrow

9° E of 0°/N to compensate for the +9° declinationNot a big deal when we are close, but over distance it

can lead to significant inaccuracies.Topo maps should indicate a declination chart on them

Set the bearing on the compass dial.Lay the long edge of the compass on the

known point (where the bearing was taken from).

Turn the compass plate so that the north lines align with the north lines on the map.

Align the base plate with an imaginary line between two points on the map.

Turn the compass dial until the north lines align with the north lines on the map.

Read the bearing set on the compass dial. Be aware then of magnetic declination and

whether your compass is measuring magnetic north or has been adjusted to grid north.

Topo maps and navigation for the purpose of locating wildland fires is not difficult.

However, it is a skill that needs to be practiced on a frequent basis to remain proficient

Utilize what you have learned and practice your skills

Once you are re-familiarized with finding bearings on a map, you will remember how triangulation works

Practice these skills as a company