NAVIGATION: PACE AND COMPASS
Wayne Powell
LEARNING OBJECTIVES:
 Students will apply azimuth direction in real-world navigation
 Students will be able to set magnetic declination
 Students will be able to navigate using pace.and compass techniques
PREREQUISITE KNOWLEDGE AND SKILLS:
 Students must have completed the following labs:
’Maps: Direction, Scale, Latitude & Longitude’
PRE-LAB PREPARATION:
 Review azimuth direction from ‘Maps: Direction, Scale, Latitude & Longitude’.
 Read the section entitled ‘The Geographic North Pole and the Magnetic North
Pole’ in this lab
MATERIALS FOR STUDENTS TO BRING:
 Calculator
Copyright © 2006 Wayne Powell
1
To navigate from one place to another you need two pieces of information: direction and distance. To travel
around within the city we usually give directions in terms such as left-right, uptown-downtown, or perhaps
east-west. You might describe distance in terms of blocks, subway stops, or perhaps miles. The ability to
provide precise estimates for direction and distance, and the ability to locate exact positions in any
environment are essential skills for a geologist, and for everyone for that matter, and so we need to have
more accurate ways to describe direction and distance than vague and variable values such as blocks.
As was described in “Maps: Direction, Scale, Latitude and Longitude”, geologists describe direction
according to the number of degrees clockwise from north, a system known as the azimuth system. East is
090º. West is 270º. South is 180º. North is either 0º or 360º. Azimuth direction allows you to be exact in
your description of direction. For example, in Figure 1 you can see that Albany is 092º from Buffalo,
whereas to fly to Brooklyn from Buffalo you would travel along a line at 121º.
FIGURE 1: Examples of
azimuth directions between
locations in New York
State.
The Geographic North Pole and the Magnetic North Pole
Azimuth is based on the angle from north, so it is necessary to find north. For
that we use a compass. A magnetic compass is a very simple device that consists
of a small, lightweight, magnet needle balanced on a nearly frictionless pivot
point. This needle will rotate until it is aligned with Earth’s magnetic field such
that one end will point towards the magnetic north pole.
Earth has a weak magnetic field that emanates from its molten outer core. The
generation of this magnetic field is a complex phenomenon related to movement
of molten metals in Earth’s outer core. In this exercise we are concerned only
with Earth’s magnetic field as a means of navigation and so we can conceptually
simplify our discussion and imagine a simple model of Earth as a spinning ball
in which a giant bar magnet has been embedded (Fig. 2). The points on the
earth's surface to which the two ends (or poles) of this 'magnet' point are called
the magnetic north pole and the magnetic south pole. It is toward these magnetic
poles that the ends of the compass needle point. The north end of the compass
needle points towards the magnetic north pole and the south end towards the
magnetic south
2
FIGURE 2: Model Earth showing relationship
between geographic and magnetic poles
The magnetic north pole and the geographic north pole lie relatively close to each other, but are not
coincident (Figs. 2 and 3). The magnetic north pole currently lies offshore of Canada’s arctic islands and is
moving to the northwest at 40km per year.
FIGURE 3: Location of the
Magnetic North Pole (MNP) in
2005, 1972 and 1904,
in relation to the position of the
Geographic North Pole (GNP)
The needle of a compass in New York City will point toward
the magnetic north pole (along the dashed arrow in Figure 4)
rather than the geographic north pole (along the solid arrow in
Figure 4). These arrows diverge by 13.5º, such that a compass
in New York City would point 13.5º to the west of where we
would really want it to point. This difference between true
north (the axis around which the earth rotates) and magnetic
north (the direction in which the needle of a compass points) is
called the magnetic declination, and it includes a magnitude
(number of degrees) and a direction (east or west).
The magnetic declination changes with position around the
Earth. In Brooklyn your compass will point 13.5W of the true
north (geographic north pole), whereas in San Francisco a
compass will point 15ºE of true north (Fig. 5). From New
Orleans, the magnetic north pole lies in front of the geographic
north pole and so a compass needle would actually point to true
north (a magnetic declination of 0º). Therefore, to get accurate
measurements of direction from a compass, you must know the
magnetic declination for your locality and correct your
3
compass accordingly.
of the reading
FIGURE 4:. The position
geographic (GNP) and magnetic
(MNP)
north poles relative to New York
City.
FIGURE 5: Magnetic declination values across the coterminous United States.
Using a Compass
Although all magnetic compasses work on the same principle, that the magnetic needle will point to
magnetic north, the specific procedures to adjust for magnetic declination and to take readings of direction
may vary from one model of compass to another. For this lab exercise you will be using the Brunton 9020G
"Classic" compass. The key parts of this compass with which you must be familiar are labeled in Figure 6.
4
FIGURE 6: Parts of a compass
5
Setting Magnetic Declination
Before a compass can be used to measure
meaningful directions, the compass must be
set to correct for the magnetic declination.

Determine the magnetic declination of
your location. This can be done from a
topographic map, or a map such as that
shown in Figure 5. The magnetic
declination for New York City is
13.5ºW.

With thumb and index finger of one
hand, hold the degree dial at N and S

With your other hand, hold the
declination dial with your thumb on the
top, and your index and middle fingers
underneath.

Twist the degree dial so that the
orienting arrow points to N

If the magnetic declination is west, twist
the degree dial counter-clockwise so that
FIGURE 7: Examples of magnetic declination
settings
the orienting arrow points to the value of
on a Brunton 9020G compass. (a) A west declination
your magnetic declination (e.g., 25ºW in
(b) An east declination.
Figure 7a). (Note that every large tick on
the degree dial is 10º, and every small tick is 2º.)

If the magnetic declination is east, twist the degree dial clockwise so that the orienting arrow points to
the value of your magnetic declination (e.g., 40ºE in Figure 7b).
Taking a Bearing on a Landmark
To determine the direction between your current position and a
distant landmark do the following:

Make sure that the magnetic declination has been correctly
set on the compass

Aim the direction arrow at the landmark of interest (e.g.,
the factory in Figure 8)

Rotate the degree dial until the floating magnetic needle
lies within the orienting arrow (shed) such that the red end
of the magnetic needle (north pole) coincides with the
pointy end of the orienting arrow

Read the number from the degree dial that lines up with
the index line. That is the azimuth bearing to the landmark.
6
FIGURE 8: Example of taking a bearing on
landmark with a Brunton 9020G compass
Navigating to Locations from Azimuth Directions
If you know the direction that you need to travel, then you can use your compass to find the bearing of your
path by doing the following:

Make sure that the magnetic declination has been correctly set on the compass

Rotate the degree dial until your target azimuth direction (e.g., 260º) lines up with the index line

Hold the compass in front of you and start to turn around
until the floating magnetic needle rotates into the orienting arrow (shed) such that the red end of the
magnetic needle (north pole) coincides with the pointy end of the orienting arrow

Let your eyes move forward from the direction arrow and note a landmark that lies along this line

Begin walking toward this landmark and count the number of paces that you take in order to determine
the distance that you have traveled
Exercise
Determining Your Pace Length
Geologists commonly determine the distance that they walk between study localities (e.g., sample
stations, rock outcrops) based upon the number of steps that they take. Figure 9 depicts 6 footprints:
feet together, right, left, right, left. These footprints record 4 steps (each time a foot touches down) or 2
paces (each time the same foot touches down). Geologists usually lead with their right foot and count
each time their left foot touches down while walking along a traverse, thereby counting the number of
paces taken. This is called pacing. If you know how many paces you have taken, and you know the
average length of your pace, then you can calculate the distance that you have walked:
Distance Walked = (Number of Paces) x (Length of Pace)
FIGURE 9: Steps and paces

Start in front of the stairs to the main entrance of Ingersoll Hall where the concrete sidewalk meets
the asphalt pathway

Begin walking in a straight line across the quadrangle to the edge of the concrete sidewalk in front
of Boylan Hall

Count the number of times that your left foot touches down (paces) while walking to Boylan Hall
and record this number
7

Walk back across the quadrangle to Ingersoll Hall, again counting the number of paces that you
take. Record this number

Average these two results and record your answer

The length along the asphalt pathway between concrete sidewalks across the quadrangle is 50
meters
Number of Paces to Boylan Hall:
__________
___________
Average Number of Paces to Cross Quadrangle:
Number of Paces to Boylan Hall:
___________
Pace Length = 50 meters / (Average Number of Paces to Cross Quadrangle
= 50 meters / _______________
= ________________________ meters
Determining Direction and Distance between Landmarks

If you have not done so already, begin by setting the magnetic declination of your compass to 13.5º
West by following the instructions provided earlier in this lab.

Confirm that you have correctly set your magnetic declination by taking a test reading.

o
Stand directly in front of one of the hand rails on the stairs of Ingersoll Hall
o
Take a bearing on the hand rail on the stairs of Boylan Hall that is directly across the Quad from
you by following the instructions provided earlier in the lab.
o
You should get a bearing of approximately 350º. If you do not, ask your instructor for assistance
Once you have confirmed that your compass is set correctly navigate between the pairs of landmarks
listed in the table below, recording the compass bearing and the distance between each pair. These 6
assigned navigation tasks may be done in any order.
Starting Location
Destination
Bedford Avenue Gate
Boylan Hall Main
Steps: Bottom, Center
Water Fountain near
Bedford Gate
Ingersoll Hall Main
Steps: Bottom, Center
Martin Luther King Jr.
Statue
Water Fountain at East
End of Ingersoll Hall
Boylan Hall Main
Steps: Bottom, Center
Water Fountain at East
End of Ingersoll Hall
Direction
(Degrees)
Distance
(Paces)
Distance
(Meters)
8
Ingersoll Hall Main
Steps: Bottom, Center
Martin Luther King Jr.
Statue
Bedford Avenue Gate
South Flag Pole
Finding Landmarks based on Direction and Distance (Orienteering)

In this exercise you will practice similar compass skills. However, this time are provided with
directions between two points (starting point, direction, and distance in meters), and your goal is to
record in the table below the feature/landmark that lies at the end of your directed path.

These 6 assigned navigation tasks may be done in any order.
Starting Position
Direction
(Degrees)
Distance (Meters)
Bedford Avenue Gate|
70
67
Martin Luther King Jr.
Statue
280
60
Center of Quadrangle
(Intersection of
Walkways)
300
32
Main Door of Library
275
100
South Flag Pole
260
42
Water Fountain at by
Bedford Avenue Gate
100
117
Destination Landmark
9