navigation

Route Selection and Navigation

Direction Determination

North

• True North- line through North Pole.

• Magnetic North- direction to northern magnetic pole.

• Grid North-North as established by map maker.

TrueNorth

MagneticNorth

GridNorth

True North• By Sighting Polaris, a Star located almost over North Pole. • Northerly direction along a line of longitudeA gyrocompass is a compass finds North by using an fast spinning wheel and

friction forces in order to exploit the rotation of the Earth. • Find true North, i.e. the direction of Earth's rotational axis, as opposed to

magnetic North• Not affected by metal

Magnetic NorthMagnetic North• North Arrow of Magnetic compass align North-South with earth’s magnetic

line of force.• North magnetic pole currently located in Northern Canada (1227 Km from

Geographical pole i.e. Pole of Rotation)• Compass: Determines direction using a magnetic north needle pivoting 360

degrees and pointing to magnetic north

Isogonics chart

http://www.centennialofflight.gov/essay/Dictionary/Poles/DI81.htm

The Agonic Line is the line of zero degree variation

Declination angleDeclination angle

Magnetic declination

• The angular distance between north and magnetic north

• Degree of declination depends on geographic location

• True and magnetic north are the same at Agonic line

MAGNETIC NORTH

TRUE NORTH

GRID NORTH

Grid North

• The direction of a grid line which is parallel to the central meridian on a map.

• Grid North may not match true north because a map is a flat representation of a curved surface.

• Grid North pertains to the north for a specific plane coordinate system. All north-south lines run parallel to one another in the UTM projections.

Types of compass• Azimuth: 0 to 360 degrees, bearings

– Read in clockwise direction from north• Quadrant: 0 to 90 degrees, bearings

– read eastward or westward of the north or south direction• Mariner’s compass: 32 bearings

– Also called a compass rose• Converting exercise

Direction Designation

Types of Azimuth• An azimuth is an angle measured clockwise from a base line

direction (north).• Defined as a horizontal angle measured clockwise from a

baseline• Types of azimuth:

– Orthodrome based on true north – magnetic azimuths based on magnetic north – grid azimuths measures with grid north as base

• Bearing: Same as a azimuth but representedusing North or south as a baseline

• Back bearing: the 180-degree opposite of the azimuth or bearing. Also known as back azimuth.

Azimuths (cont.)Grid azimuth =

45 degrees

546000mE

3818

000m

N

19

20

22

21

23

47 48 49 50 51 52 53 54

GGNN

Orthodrome

A great circles arc that is A great circles arc that is casted between two casted between two points on a surface of a points on a surface of a sphere. Is the shortest sphere. Is the shortest geodetic connecting line geodetic connecting line between two points on a between two points on a sphere.sphere.

Measuring an AzimuthProtractors

Measuring an AzimuthCompasses

302010

W

E

E. decl.

W.decl.

mm

BASE PLATE

DIRECTION OFTRAVEL ARROW

BASE LINE

INDEX LINEORIENTEERING

ARROW

ROTATINGDIAL

FLOATINGMAGNETIC

NEEDLE

ORIENTEERINGLINE

N

S

11

/ 21

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Magnetic Lensatic Compass(Military Type)

Silva Polaris Compass(Civilian Orienteering)

Direction - Some ExamplesWhere is north onthis map?

Where is north onthis map?

Position Determination

• Land OperationLand Operation Water Operation Water Operation

Resection method

• Resection is the method of locating one's position on a map by determining the grid azimuth to at least two well-defined locations that can be pinpointed on the map.

• For greater accuracy, the desired method of resection would be to use three or more well-defined locations.

http://www.map-reading.com/resect.php

Nautical Charts• Used for marine navigation and contain information on all

navigational aids, such as buoys and beacons, lighthouses, radio and radar stations, shipping channels, restricted areas.

• Types of nautical charts: – Sailing charts are used to fix a position in long-distance navigation.

They usually employ Mercator's projection. – General charts of the coast are used the same as sailing charts and

also for near-shore navigation. They employ Mercator's projection. – Coast charts are used for coastwide navigation and to approach a

shore from a long distance offshore. They show details of land formations and artificial landmarks which help fix positions.

– Harbor charts are used to navigate harbors and their approaches. They greatly detail terrain and artificial objects.

Buoys - floating objects that are anchored to the bottom. Beacons -Which are structures that are permanently fixed to the sea-bed or land.

http://www.boatus.org/onlinecourse/ReviewPages/BoatUSF/Project/info5d.htm

Nautical Charts

Symbols used in Nautical Charts

Position Determination• Lines of Position: The modern chart shows us positions of

many recognizable navigation aids like churches and lighthouses, which facilitate the approach to a coastal area.

• Ranges: A precise way to obtain a Line of Position (and without a compass) is to locate two navigational aids in line.

Position Determination

• Fix is the ship's position on the earth at some given point in time. A fix is determined by the simultaneous intersection of Line of Positions.

• Dead reckoning is a technique to determine a ship's approximate position by applying to the established charted position a vector or series of vectors representing true courses and speed.

LORAN (LOng RAnge Navigation)

• LORAN is a position-fixing system consisting of an array of fixed stations that transmit precisely synchronized signals to mobile receivers.

• Fixed difference in the time of arrival of the signals from any two stations will define a hyperbolic arc on which the receiver must lie.

Global Positioning System

• The Global Positioning System (GPS) consists of a constellation of satellites that broadcast two pieces of data to radio-navigation receivers. A receiver determine the precisely-known position of these satellites at the same time, then the receiver could precisely determine its own position through triangulation.

Aeronautical charts• Contain a great deal of data on ground features, with an emphasis on

such things as landmarks, elevations, heights of obstructions, airports, and airways.

• World Aeronautical Charts (WAC) based on Lambert Conformal Conic projection are used for flight planning and in-flight navigation by VFR pilots on extended cross country flight at low to medium altitudes and medium to high airspeed.

• Sectional Aeronautical Charts: Series of charts based on Lambert Conformal Conic projection covering the United States at a scale of 1:500,000. The topographic information consists of contour lines, shaded relief, drainage patterns, and an extensive selection of visual checkpoints and landmarks. Cultural features include cities and towns, roads, railroads, and other distinct landmarks. The aeronautical information includes visual and radio aids to navigation, airports, controlled airspace, special-use airspace, obstructions, and related data.

Aeronautical charts

World Aeronautical Charts

Sectional Aeronautical Chart

Terminal Area Charts

Helicopter Route Charts