SAR Fundamentals/Navigation instruments theory

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1 Subject
2 Authors
3 Scope
4 Prerequisites
5 Objectives
6 Time Plan
7 Aids
8 Question bank
9 Frequently Asked Questions
10 Feedback
11 License
12 Reference Material
13 Notes
14 To Do

Subject

What is this lesson plan about?

This lesson gives the students a theoretical (class room) understanding of the instruments that they may be using in the field to aid navigation.

The instruments covered are:

compass
GPS
altimeter
stride tally counter

For each instrument, the theory of how it operates is discussed along with how to select an instrument for purchase.

Authors

List who wrote this lesson plan.

Brett Wuth

Scope

What is included in this lesson, what's not and why.

SAR Fundamentals Ch.13 "Navigation"

Basic SAR Skills Manual: Ch.7 "Navigation"

stride count

Only basic use of a GPS is shown. Advanced features such as waypoints, tracks and maps are left to another lesson beyond the SAR Fundamentals course.

Waypoints are not an essential skill for using GPS. Students should be recording locations on paper, and should be able to estimate relative direction and distance to a new location.
- This material can be covered in additional material presented by a SAR group outside the SAR Fundamentals course.

Prerequisites

What should students already know/have accomplished before the lesson is presented.

Prior to this lesson, students should have already been introduced to the following concepts:

direction measured in degrees
directions measured from True North (this lesson will introduce declination and magnetic north)

Parts of a compass which can be used on a map

straight edge
ruler
rotatable bezel and interior north-south lines
roamer
magnifying lens

Specifying a location in UTM

the three components of a UTM: Zone, Easting, Northing
map datums: NAD27 vs WGS84
the 6 digit short form of UTM

elevation

contour lines

Objectives

At the conclusion of this lesson the participants will be able to:

explain how a GPS works
identify purposes for which a GPS is sufficient, a help, not useful
identify circumstances under which a GPS may fail
identify the significant configuration options of most GPS models
identify when to use NAD27 vs. NAD83/WGS84
configure a particular model of GPS for local SAR usage
read a UTM off a particular model of GPS and translate that to and from the UTM notation used with topographic maps.
determine the UTM of the location where they are at and the accuracy of their reading
given a destination UTM know what direction and distance to go to get to it
select a GPS for purchase
identify the parts of a compass
explain how a compass works
select a compass for purchase

Time Plan

Total Time: 1 hour 45 minutes

2013-02: 1 hour 16 min

See:

Time

Material

00:00

3 min

Introduction

Introduce topic title

Introduce Instructor

Present Objectives

Determine experience level of students.

Who uses GPS regularly?
Who uses a compass regularly?
Who is comfortable reading UTM's off a map?
Recruit more advanced students to assist in illustrating material.

00:03

1 min

Instruments

SAR workers use navigation instruments to make measurements in the field.

The measurements are used to calculate your location or that of other things.

The four instruments we will discuss:

pace counter
compass
altimeter
GPS

No one instrument is perfect. Each is better in some circumstances.

Each instrument has different ways of failing.

00:04

2 min

Pace Counter

Measuring distance with your feet.

When a GPS isn't working this is the best that can be done in the field.

Will be practiced in a separate exercise.

Pace is landing with the same foot.

Need to count each pace.

beads - slide bead on every 10 paces. Slide other for every 100 paces.

pedometer - measures the jiggle from each pace.

alternatives:

count in your head
use note book.
less accurate: know your speed and measure your time.

00:06

1 min

Compass

So far having been using the compass on the map.

Can also be used in the field. Because of magnetic needle.

00:07

2 min

Magnetic North

The needle of the compass points in the direction of Magnetic North towards the North Magnetic Pole.

This is not the same as True North. The North Magnetic Pole isn't the same location as the north pole.

North Magnetic Pole is currently (2012) 85.9 deg N 147.0 deg W northwest of of the tip of Ellsmere Island.

It moves. About 55 km closer to Russia each year.

00:09

4 min

Declination

The difference between True North and Magnetic North is called Declination.

It's expressed in degrees and fractions of degrees (minutes).

If Magnetic North is to the east of True North, the declination is degrees EAST. Opposite is degrees WEST.

Declination changes from year to year.

It also changes from area to area.

Pincher Creek has about half a degree more declination than Lethbridge.
Banff is about one degree more declination than Pincher Creek.

*Navigation/Declinations:*
Pincher Creek, February 2020: 13 deg 38' E Lethbridge, February 2020: 13 deg 12' E Banff, February 2020: 14 deg 36' E

Look up online Declination: http://magnetic-declination.com/

Calculation on topo maps is old, not accurate.

Ask the person briefing you.

00:13

4 min

Compass failures

Compasses don't work:

when there's magnetic distrubances

other magnets nearby
things that generate magnetic fields
- power lines
- generators, electric motors

attracted to certain metals

don't hold close to building, vehicle, belt buckle

when the needle doesn't settle

don't use when vibrating, turning

when the needle scrapes the housing

doesn't work close to magnetic poles because needle points down
the further from the equator, the more the magnetic field points down
compass needles are built for zones
- don't use a compass from the southern hemisphere in the northern hemisphere
unless compass has "Global" needle bearings

00:17

7 min

Choosing a compass

Features to look for in compass:

straight edge
ruler (scale)
roamer
bezel (barrel) in 360 degrees (not 4 x 90 degrees, mils, or named directions)
interior north-south lines
adjustable declination
nice: magnifying lens
sighting mirror
- sighting line
- sighting notch
  - nice: both top and bottom of mirror
needle zones (nice: Global)
nice: luminous
nice: clinometer

Good compasses:

SUUNTU MC-2G
Silva Ranger
approx $70

00:24

4 min

Altimeter

Measures the weight of the air above you - air pressure.

The higher you go up, the less pressure - displays elevation is feet or meters.

Air pressure also affected by weather - high and low pressures

needs to be recalibrated when the weather changes

Can be bought as separate device, or built into watches, radios, cell phones.

Does not require clear view of sky. Works when GPS's fail. Works indoors, in caves.

Only useful when elevation helps is determining location.

e.g. following a feature (ridge line) until hit certain elevation
e.g. traversing along same elevation until hit certain feature (creek)
terrain has a lot of elevation details : big hills, mountains : Kananaskis, Waterton, BC

00:28

1 min

Satellite navigation systems

There are two satellite navigation systems available

GPS - Global Positioning System
- controlled by the US military
- most commonly used
GLONASS - Global Navigation Satellite System
- controlled by the Russian military
- starting to be found in devices
- works substantially the same as GPS and can be combined

Other systems will soon arrive from the Chinese and the Europeans.

00:29

3 min

How a GPS works

3 major components

1. radio receiver
- compares time for radio signal to arrive from satellites
- receives information on satellite locations
- optional WAAS: receives corrections to satellite location, signal distortions
2. computer
- computes where GPS currently is (needs 4 separated satellites)
  - 10-15m accuracy
  - applies corrections: ~ 1m accuracy
- records where GPS has been
- allows entry of remote locations
- calculates distance and direction between points
- calculate speed/time
- draw a route on a map
- place points on map
3. magnetic sensor (only some models)
- determines direction GPS is facing
- GPS without magnetic sensor tells what direction GPS has moved, but not direction GPS is facing
- test GPS by turning it. Does the direction arrow change?

00:32

10 min

How a GPS fails

radio signal not received from 4 satellites

heavy tree cover
blocked view of sky (hills, mountains, building)
blocked view of geosynchronous WAAS satellites (32 deg elevation around Pincher Creek)
- North America only
satellites not in right positions (below/at horizon, clustered)
satellites not working/disabled (military selective availability)
radio interference (jamming; spoofing)
multipath (reflected) signals[3]
weather does not affect signal

computer fails

batteries (-15C)
temperature (too hot)
water/condensation (if not sealed)
electromagnetic interference (industrial sites)

magnetic sensor fails (same as compass)

metal (belt buckles, cars)
magnetic fields (power lines)
magnetic anomalies (far north)

00:42

4 min

Alternatives/Aids to GPS