1. Fundamentals of Nav
ATC Chapter 1

2. Aim To introduce the Concept and Fundamentals of Visual Navigation
7.1 Form of the earth
In order to apply this knowledge a student should have an understanding of the items listed in (a) to (h) and, if applicable, their effect on:
position on the earth
time differences
distance and direction
(a) the shape and rotation of the earth
(b) latitude, longitude
(c) meridians of longitude, parallels of latitude
(d) equator, Greenwich meridian
(e) great circles, small circles, rhumb lines
(f) difference between true and magnetic north
(g) terrestrial magnetism, magnetic variation and the change in variation with time
(h) distance on the earth i.e. relationship between a minute of latitude and a nautical mile.

3. Objectives Define “Visual Navigation and Dead Reckoning Navigation”
Describe the “Form of the Earth”
Identity our position, the direction we wish to travel and the distance we want to fly
Describe and calculate our air speed and velocity through the air
Calculate and describe our altitude above the surface of the Earth

4. 1. Definitions
Visual Navigation is fun, challenging and very satisfying if done properly.
Australia can be characterised as follows
A sparse population with our capital and other major cities concentrated along the coast, principally in the eastern states
Many towns on charts are very small and easy to confuse with other towns
A lack once away from the coast of easily recognisable land features due to the generally flat terrain and lack of trees, vegetation, rivers or other easily distinguishable features especially as you move further inland
There are few Navigation Aids such as a VOR or NDB as you move further inland

5. How to successfully navigate your way around Australia
1. Definitions
How to successfully navigate your way around Australia
Understand the concepts and principles involved in Visual Navigation
Plan your flight carefully before you depart
Be organised and disciplined in your approach in flight to navigating from your take off point to your destination
Be “ahead of the aircraft” by which we mean anticipating what needs to be done in the next few minutes and calculating contingencies to cope with unexpected events

6. 1. Definitions Visual Navigation
Visual Navigation is where pilots use aviation charts (maps) to match observed ground features to determine the position (fix) of the aircraft
Visual Navigation is based on a pilot:
Being able to sight sufficient ground features be able to fix the position of the aircraft at not less then 30 minute intervals
Navigation Aids such as a GPS, VOR, NDB may be used to assist in determining the position of the aircraft but the prime means of navigating is by Dead Reckoning

7. 1. Definitions Dead Reckoning
Dead Reckoning (DR) is the process of calculating one's current position by using a previously determined position, or fix and advancing that position based upon known or estimated speeds over elapsed time
Dead Reckoning is based on a pilot:
Flying accurately the Headings (HDG) which have been previously calculated
Knowing the elapsed time flown since the last known position
Being able to closely estimate the achieved Ground Speed (GS)
Accurate chart (map) reading to initially identify your position based on time elapsed and then confirming your position by reference to ground features

8. 2. Form of the Earth Shape and Movement
The Earths shape can be described as an “oblate spheroid”
It is flattened at the Poles, the surface is constantly changing due volcanic, seismic and tidal activity
For practical navigation purposes we can describe the earth as a perfect sphere
The Earth rotates eastward on its Polar Axis
The 2 points where this axis meets the surface are the North and South Geographical Poles (True North or True South)

9. 2. Form of the Earth Great Circles
A Great Circle is a circle drawn on the surface of the Earth with a plane that passes through the centre of the Earth
Examples include:
Meridians of Longitude
The Equator
Horizontal Paths of Radio Waves
A Great Circle divides a sphere into equal parts
A Great Circle is the shortest path between 2 points on the surface of a Sphere such as the Earth
Point out that only one parallel of Latitude can be a Great Circle eg the Equator

10. 2. Form of the Earth Small Circles
A Small Circle is a circle drawn on the surface of the Earth that is not a Great Circle
The centre of a Small Circle is not at the centre of the Earth
Small circle of a sphere

11. 2. Form of the Earth Rhumb Lines
In navigation, a rhumb line is a line crossing all meridians of longitude at the same angle
On a plane surface this would be the shortest distance between two points.
Over the Earth's surface at low latitudes or over short distances it can be used for plotting the course of a vehicle, aircraft or ship
For practical purposes a Great Circle direction and a Rhumb Line direction may for distances under 200 nm be considered the same.
Ask what type of charts do we use in Navigating
WAC - Lambert Conformal – 1: 1,000,000
VNC – Lambert Conformal – 1: 500,000
VTC – Transverse Mercator Projection – 1: 250,000
Image of a rhumb line, spiralling towards the North Pole

12. 2. Form of the Earth Longitude
All Great Circles containing the Polar Axis are “Meridians of Longitude”
The prime meridian, based at the Royal Observatory, Greenwich in the UK, was established by Sir George Airy in 1851
Meridians of Longitude are specified by their angular difference in degrees East or West of the Prime Meridian
The Prime Meridian is either 0° if on the Atlantic side of the Earth or 180° degrees if on the Pacific Ocean side of the Earth
If you divide 360° by 24 hours, you find that a point on Earth travels 15° of longitude every hour

13. 2. Form of the Earth Latitude
Lines of constant latitude, or parallels, run east–west as circles parallel to the equator
Latitude is an angle which ranges from 0° at the Equator to 90° (North or South) at the poles

14. 3. Position, direction and distance
Position Fixing
Latitude is used together with Longitude to specify the precise location of features on the surface of the Earth
By convention a position is reported in the following format;
Latitude in Degrees, Minutes, Seconds, N or S of Equator
Followed by
Longitude in Degrees, Minutes, Seconds, W or E of the Prime Meridian
Seconds can be replaced by decimal parts of a minute eg 6 Seconds = 0.1
See handout Nav Chapter 1-1

15. 3. Position, direction and distance
Direction is the angular position of one point to another
We need a datum point to establish a reference point and for our purposes we use a North-South Line through our current position (local meridian)
By convention we use a flat circle divided into 360 degrees to refer to specific Headings (HDG) to our destination
See handout Nav Chapter 1-1

16. 3. Position, direction and distance
Describing Direction
The 4 Cardinal Points are;
North as 000, South as 180,
East as 090, West as 270
In between are all the other
points of the compass
A HDG of 300 is where on the
diagram?
A HDG of 115 is where on the
See handout Nav Chapter 1-1

17. 3. Position, direction and distance
True North
Our initial reference point for calculating
the HDG to fly is True North or the
North Geographic Pole
This makes it easy to measure
angles and plot and measure
tracks on our Navigation Charts
However we normally do not
have an instrument in our aircraft
that can display our HDG relative
to True North

18. 3. Position, direction and distance
Magnetic North
We have in our aircraft a compass that can display our HDG relative to Magnetic North
The Iron Core of the Earth acts as a huge magnet with the 2 magnetic poles being Magnetic North and Magnetic South
Currently the Magnetic North Pole lies in Hudson's Bay, Canada and it is currently moving toward Russia at between 55 and 60 km per year
The difference between True North and Magnetic North is the Magnetic Variation and varies depending on the location of your aircraft
Movement of Earth's North Magnetic Pole across the Canadian arctic, 1831–2001

19. Illustration of the Magnetic Field of the Earth
3. Position, direction and distance
Illustration of the Magnetic Field of the Earth

20. 3. Position, direction and distance
Magnetic Variation
Navigation Charts display lines of equal Magnetic Variation, called Isogonals
We adjust our planned True HDG to a Magnetic HDG by allowing for the Magnetic Variation to give us the Magnetic Track (TR) we need to follow to arrive at our destination
Variation is labelled east or west depending on whether the Isogonal is east or west of the Agonic Line (zero magnetic variation)
If variation is East, magnetic direction is less than true
If variation is West, magnetic direction in more than true
(East is least, West is best)
Use VNC to illustrate Isogonals

21. 3. Position, direction and distance
Magnetic Deviation
Magnetic deviation refers specifically to compass error caused by magnetized iron within a ship or aircraft.
This iron has a mixture of permanent magnetization and an induced (temporary) magnetization that is induced by the Earth's magnetic field.
To calculate the magnetic deviation for an aircraft compass is “swung” at regular intervals using specific procedures.
The outcome is a calibration chart which is displayed on or by the compass.
The deviation is generally minor , less than 2 degrees.

22. 3. Position, direction and distance
Distance Measurement
For Navigation we use Nautical Miles to measure distances
1 Nautical Mile (nm) is the length, at the Earth's sea-level surface, of one minute of arc of a great circle
The International Nautical Mile is 1,852 metres or 6,076.1 feet
Consequently, one degree of latitude (measured along a meridian) has an equivalent surface distance of 60 nautical miles
For other Horizontal Distances we use Kilometres or Metres, for example Runway length, visibility, horizontal distance from cloud
For Vertical Distances we use Feet, for example Altitudes to fly and vertical separation from clouds

23. 4. Calculate Air speed and Velocity
We fly in a mass of air that will move in accordance with the direction of the wind and its velocity.
To accurately navigate we need to understand how the wind affects the path and speed of our aircraft over the ground.
The 4 speeds we are interested in are:
Indicated Airspeed (IAS)
Calibrated Airspeed (CAS)
True Airspeed (TAS)
Groundspeed (GS)

24. Total Pressure – Static Pressure = IAS
4. Calculate Air speed and Velocity
Indicated Airspeed
Our Airspeed Indicator (ASI) in the C172 compares the total pressure measured by the Pitot Tube of the air due to its movement relative to the aircraft with the static pressure measured by the Static Vent.
Total Pressure – Static Pressure = IAS
The reading you obtain from the ASI is affected both by the speed and the density of the air.
For manoeuvring the aircraft we use IAS as displayed by the ASI. For example flap limiting airspeeds and approach airspeeds

25. 4. Calculate Air speed and Velocity
Calibrated Airspeed
Our Airspeed Indicator (ASI) in the C172 is subject to 2 types of errors;
Instrument Error
This type of error is a result of friction within the instrument and/or bad design.
Position Error
The location of the Pitot Tube and the Static Vents are critical to the accuracy of the ASI. Incorrect positioning may lead to errors when the airflow in the vicinity of the Pitot Tube and Static Vents is disturbed for example by lowering flaps.
Calibration Table
The ASI is “calibrated” and the results are used to provide a Calibration Table for pilot use to aid in interpreting the ASI. In practice the errors are very small and we can generally assume IAS = CAS

26. 4. Calculate Air speed and Velocity
True Airspeed
For navigation purposes we need to be able to calculate the effect of changes in air temperature and air pressure on our speed through the air. Once calculated this gives us our True Airspeed (TAS)
The ASI is calibrated in accordance with the international standard sea level atmosphere. Changes in the air density (temperature and pressure) will mean that the ASI does not display the TAS.
Temperature Changes
The warmer the air the less dense it is. Which means the aircraft must travel faster through the air to maintain the same IAS, therefore TAS is higher.
Pressure Changes
As we gain altitude there are less molecules of air and therefore the air is less dense. Which means that as we gain altitude we will have a lower IAS for the same TAS.

27. 4. Calculate Air speed and Velocity
Calculating True Airspeed
The G1000 calculates and displays our TAS (below the IAS indicator).
We can however manually calculate the TAS with our Flight Computer.
We do that by reference to the Outside Air Temperature and the Pressure Altitude.
TAS will always be higher than IAS.

28. 4. Calculate Air speed and Velocity
Wind Velocity
A Velocity is a rate of change of position in a given direction and is therefore a combination of both speed and direction.
The speed and direction of an air mass is a velocity.
By convention wind speed and direction is provided in the following format;
Direction (3 digits)/ Speed (2 or 3 digits)
Example
A wind of 20 knots travelling from the north would be expressed as 360/20

29. 4. Calculate Air speed and Velocity
Weather Reports
Weather reports will provide wind information in the following format
Degrees Magnetic
For surface winds eg for take off or landing in an ATIS or TAF
Degrees True
For navigating through an air mass in an ARFOR
This means that we must adjust the winds we use in navigating from one place to another to take into account the Magnetic Variation.
See the Bureau of Meteorology – Aviation section for detailed information on aviation weather reporting.

30. 4. Calculate Air speed and Velocity
Groundspeed
The GS is one of the most important pieces of information a navigator needs to accurately fly to your destination.
GS is found by adjusting your TAS for the effect of wind (direction and velocity).
Example
TAS = 120 knots, HDG = 360, Wind = 360/25
Calculation – 120 knots – 25 knots of wind = GS of 95 knots
(As there is nil cross wind the calculation is simple. We will try more complex examples using the Flight Computer to calculate our GS in future lessons)

31. 4. Calculate Air speed and Velocity
Time Intervals
We use the GS to calculate a TI which in turn dictates your fuel requirements, the time you will arrive and the payload you can carry.
We can check our GS as the flight progress by comparing the time it takes to fly over 2 known points with the distance actually travelled.
Example
Distance travelled between Alpha and Bravo = 90nm
Time Interval to travel between Alpha and Bravo = 45 minutes
GS = 90/45 or 2nm per minute therefore GS = 120 knots

32. 4. Calculate Air speed and Velocity
Triangle of Velocities
The Triangle of Velocities is typically used to calculate HDG and GS
In order to use the triangle we must know at least two of the following:
Track (TR) and Groundspeed (GS)
Wind (Direction and Strength)
Heading (HDG) and True Airspeed (TAS)
Wind
Heading and True Airspeed
Track and Groundspeed

33. 5. Altimetry Vertical Navigation
Unlike driving a car when flying we operate in a 3 dimensional environment and we need to have some way to navigate both horizontally and vertically
Terrain Separation: We need to ensure we know where we are in relation to the ground to ensure a safe flight to our destination
Traffic Separation: We need to have a common system of determining our altitude to ensure separation from other aircraft
Aircraft Performance: How high or low we fly will affect aircraft performance and how efficiently we can get to our destination
See handout Nav Chapter 1-1

34. 5. Altimetry Vertical Measurement
Altitude: Measured by reference to Mean Sea Level (MSL)
For example at Parafield we fly our circuit altitude is 1,000 feet Above Mean Sea Level (AMSL) so all aircraft are at the same Altitude
Height: Measured by reference to a point above the ground
For example if we were flying above Mount Lofty at an altitude of 3,500 feet we would be at a height of 727 feet above Mount Lofty
Flight Level: Measured by reference to a common pressure datum of hPa
For example above 10,000 aircraft set 1013 hPa on their Altimeters and fly at “flight levels” such as FL 150 (15,000 feet)
See handout Nav Chapter 1-1
Altitude
Height
Sea
Ground

35. 5. Altimetry Altimeter Settings
QNH: Setting the Altimeter to a specified QNH will indicate aircraft Altitude (AMSL)
QFE: Setting QFE (Field Elevation) will determine the altitude above the ground
Note: QFE is normally only used in some recreational aviation activities such as aerobatics or parachuting
ISA Pressure: The International accepted standard pressure at sea level is “ hPa”
This is used to establish “flight levels” for aircraft flying at high altitude, for example in Australia above 10,000 feet, in the USA above 18,000 feet
See handout Nav Chapter 1-1

36. 5. Altimetry QNH Settings
We set the actual pressure or “QNH” before take off as the actual pressure is seldom the same as the ISA standard of
Setting the QNH on the Altimeter sub scale will provide the pilot with the actual altitude of the airfield and in flight the altitude of the aircraft AMSL.
Pressure Changes
During the day the actual pressure will change and according the actual QNH will change.
Pressure changes are advised in aviation weather forecasts, by ATC and by an airfield ATIS.
If we are on the ground we can determine the QNH by setting the known airfield height above mean sea level and reading the QNH off the altimeter sub scale.
See handout Nav Chapter 1-1

37. 5. Altimetry Selection of Altitudes
VFR Hemispherical
Altitudes Below 10,000 Feet
Magnetic Tracks
Cruising Altitudes
(Area QNH)
1,500
3,500
5,500
7,500
9,500
2,500
4,500
6,500
8,500
Hemispherical Cruising Altitudes are optional below 5,000 feet however it is recommend that wherever possible hemispherical altitudes should be flown
See handout Nav Chapter 1-1
Why is it important to fly at the correct altitude?
IFR aircraft fly at Evens or Odds Altitudes

38. VFR Hemispherical Cruising Levels Above 10,000 Feet
5. Altimetry
Selection of Cruising Levels
VFR Hemispherical Cruising Levels Above 10,000 Feet
Magnetic Tracks
Cruising Levels
(1013 hPa)
115
135
155
175
195
125
145
165
185
FL 115 is not available when the Area QNH is less than 997 hPa
FL 125 is not available when the Area QNH is less than 963 hPa
See handout Nav Chapter 1-1
Oxygen is required for flight above 10,000 feet.
VFR flight is prohibited above 20,000 feet.

39. Questions?