Basic Map and Compass Skills:How to Navigate in the Backcountry

Fox Cities Backpackers Meetup

Note: I shamelessly stole most of the graphics in this presentation from various websites.I know that makes me a bad person… I’ve listed the various sites on the last slide. I’m a geek, not a graphic artist. I actually LIKE clip art .

By Ken Stuber

Maps

• Only useful for navigation if you know how to use one

• Several typeso Trail Maps: tend to show trails, trail

distances, intersections and main features, but does not show topography (at least not well, usually).

o USGS Maps: Designed for navigation, LOTS of information crammed into a small space. Can be difficult to read without practice.

o Specialty Maps: Often a hybrid of the above two types, such as the “Trails Illustrated” maps made by National Geographic. Great for trip planning and basic navigation.

What to Look for When Choosing a Map• Will you be travelling on-trail of off-trail?• How heavily used are the trails you will be on?• What is the terrain like?• In general, you’ll need a more detailed map if– Trail is lightly traveled– There is little relief, terrain is monotonous– You will be off trail at all

• What scale? – 7.5 min USGS maps 1:24,000. 1in = 2000ft– “County” series USGS maps 1:100,000. 1in=1.6mi

Contour Lines

• Two dimensional representation of three dimensional space• Lines join points of equal elevation• Contour interval is the difference in elevation between lines• Every 5th contour line is an Index Contour which may have elevation marked on it.

Reading Topography on a Map

• Shaded Relief Map

1. Looks like a stylized aerial view2. Shading gives depth, making it easy to tell mountain from valley.

Reading Topography on a Map

1. Summit – Concentric circles2. Gentle Slope – Contours spaced far apart3. Steep Slope – Contours spaced close together4. Ridge – “Arrows” pointing down hill5. Gulley – “Arrows” pointing up hill

• “Standard” Topographical Map

Reading a USGS map• Map Name• Year of Production and

Revision• General location in State• Next Adjacent Quadrangle

Map• Map Scale• Distance Scale• Contour Interval• Magnetic Declination• Latitude and Longitude

Reading USGS Map Features and Terrain

• Black - man-made features such as roads, buildings, etc.

• Blue - water, lakes, rivers, streams, etc.• Brown - contour lines • Green - areas with substantial vegetation

(could be forest, scrub, etc.)• White - areas with little or no vegetation;

white is also used to depict permanent snowfields and glaciers

• Red - major highways; boundaries of public land areas

• Purple - features added to the map since the original survey. These features are based on aerial photographs but have not been checked on land.

Reading USGS Map Features and Terrain

Reading USGS Map Features and Terrain

Using a Compass

• Familiarize yourself with the types of compasses, their parts and features

• A quality compass will have a movable housing, scale and orienting lines, orienting and direction of travel arrows, and declination marks.

Using a compass without a map• Find your intended direction of travel on

the compass housing• Turn the housing so that direction meets

the Direction of Travel Arrow• Hold the compass in your hand in front of

you, make sure it is perfectly horizontal and away from metal objects with direction of travel arrow pointing ahead of you

• Rotate your body until the N-S arrow on the housing lines up with the magnetic needle

• The direction of travel arrow now points in your intended direction

Using a compass with a map (step 1)

• Place the compass on the map so that the edge connects where you are with where you want to be.

• The direction arrow on the compass should point toward where you want to be.

• You can also use the scale on the compass at this time to measure distance (as the crow flies)

• Hold the compass firm on the map

• Turn the housing until the North-South lines on the map are parallel with the orienting lines on the housing

• Make sure the N-S arrow on the housing is pointing toward North on the map

Using a compass with a map (step 2)

Using a compass with a map (step 3)

• Hold the compass in your hand in front of you, make sure it is perfectly horizontal and away from metal objects with direction of travel arrow pointing ahead of you

• Rotate your body until the N-S arrow on the housing lines up with the magnetic needle

• The direction of travel arrow now points in your intended direction

Traveling on the taken bearing

• Once you have your compass set for your intended direction of travel (taken a bearing), you need to get there.

• You can simply walk in the direction the arrow points, frequently checking the compass

• Or find a feature in the landscape (Unique tree? Rock? Ridge? Hill? Lake?) that lines up with your intended direction. Walk there and repeat.

Correcting for Lateral Drift• It’s nearly impossible to walk a perfectly straight line. Your

error doing so is called Lateral Drift.• One technique is to deliberately aim left or right of your

target, walk the expected distance, and then turn toward your target in the direction you intentionally missed. This way, you ALWAYS know which direction you missed it by.

Navigating around obstacles• When you reach an obstacle, hike a

rectangle around the object – Set a new bearing 90° from your

original heading and walk until you have cleared the obstacle. For example, if your original bearing was 315°, hike a new bearing of 45°. Count your paces to track distance traveled.

– Go back onto your original bearing, parallel to your original course until you clear the obstacle along that axis.

– Set a bearing 90° back to your original bearing (in this case 225°) and walk the same number of paces.

– Now turn back to your original bearing. You will be along your original line of travel.

How do you use a Mirror Compass?

• Allows you to see the compass dial and the background at the same time

• Helps keep the compass level while taking a bearing

• Can be bulkier and weigh more…

Magnetic Declination• Maps are oriented toward ‘true north’.• True North is the northern axis of the Earth’s rotation.• Compasses orient themselves toward ‘magnetic north’• Magnetic North is where the Earth’s magnetic field re-

enters the earth, the northern ‘pole’ of the Earth’s natural magnetism.

• Magnetic North changes slowly over time, currently: – Latitude:N 82° 17' 60"– Longitude:W 113° 24' 0"

• Magnetic Declination is the measure of the difference between true north and magnetic north, allowing us to correct for it when navigating.

Magnetic vs True North

Magnetic North changes over time

Magnetic North and True North are not in the same place, declination allows us to correct for it.

So what does declination mean to us?

• You’ll need to find current declination for where you will be– http://www.ngdc.noaa.gov/geomag-web/#

declination• Then you need to adjust for it when taking a bearing• You can do this one of two ways:– Buy a compass with a settable declination screw– Add or subtract the declination from the bearing

you took on the map

Manually adjusting for declination

• Rhymes and acronyms to help remember– CEEC: Correct Easterly Errors Clockwise– LARS: Left Add, Right Subtract– East is Least(-), West is Best(+)

• With East Declination, subtract declination from map bearing to get magnetic bearing

• With West Declination, add declination from map bearing to get magnetic bearing.

• When going from magnetic bearing to map bearing, it’s the opposite!!

Sites I stole graphics from:• http://www.usgs.gov/• http://www.exploringthenorth.com/porkiesum/map.html• http://www.princeton.edu/~oa/manual/mapcompass.shtml• http://www.walkandramble.co.uk/expert-advice/how-to-read-a-map-and-compass

.html• http://www.enchantedlearning.com/geography/mapreading/topo/• http://en.wikipedia.org/wiki/Contour_line• http://www.spidercanyon.com/backiss/bimapnav4a.html• http://blog.backpackerbucks.com/gear/10-little-goodies-worth-jamming-in-a-back

pack/

• http://adventure.howstuffworks.com/outdoor-activities/hiking/how-to-read-a-topographic-map1.htm

• http://www.learn-orienteering.org/• http://www.thecompassstore.com/• http://academic.brooklyn.cuny.edu/geology/leveson/core/linksa/magnetic.html