Charting for BeginnersCharting for Beginners

Essential Questions…Essential Questions…

How do you use a compass? How do you use a compass? How do you use the tools while How do you use the tools while

charting?charting? What is the difference between What is the difference between

bearing, course, and heading?bearing, course, and heading?

Why do we ChartWhy do we Chart

A navigator is concerned with A navigator is concerned with keeping the ship in navigable waters keeping the ship in navigable waters and fully afloat at all times.and fully afloat at all times.

As the ship approaches land, the risk As the ship approaches land, the risk of danger increases as the water of danger increases as the water becomes shallow and traffic becomes shallow and traffic increases.increases.

How do you use a compass?How do you use a compass?

Types of CompassesTypes of Compasses

Gyro CompassGyro Compass• points to True North, is an expensive points to True North, is an expensive

piece of equipment piece of equipment Magnetic CompassMagnetic Compass

• points to magnetic northpoints to magnetic north• the compass needle will attempt to align the compass needle will attempt to align

itselfitself red pole pointing toward magnetic northred pole pointing toward magnetic north blue pole toward magnetic southblue pole toward magnetic south

VariationVariation

Variation is the angle between the true Variation is the angle between the true and magnetic meridians at your present and magnetic meridians at your present positionposition

Is different in different parts of the worldIs different in different parts of the world It undergoes slight yearly changesIt undergoes slight yearly changes

• it is the angle that the magnetic meridian is it is the angle that the magnetic meridian is deflected east or west of the true meridian due deflected east or west of the true meridian due to the effect of Earth's magnetismto the effect of Earth's magnetism

• is indicated on the compass rose is indicated on the compass rose

Compass DeviationCompass Deviation

Deviation is the difference between Deviation is the difference between magnetic north and compass northmagnetic north and compass north

is the amount that the compass needle is is the amount that the compass needle is deflected from the magnetic meridian due deflected from the magnetic meridian due to the effects of any "on board" magnetic to the effects of any "on board" magnetic fieldsfields

it is not a constant errorit is not a constant error• compass deviation only changes as the ship's compass deviation only changes as the ship's

head changes, these are recorded on a head changes, these are recorded on a deviation card deviation card

How do you use the tools while How do you use the tools while charting?charting?

What is the difference between What is the difference between bearing, course, and heading?bearing, course, and heading?

BearingBearing

the direction in which the object lays the direction in which the object lays measured from a reference, bearings measured from a reference, bearings of objects are taken with north as of objects are taken with north as reference and not the bow of the reference and not the bow of the boatboat

the bearing of an object can have the bearing of an object can have three different values three different values

Relative BearingRelative Bearing an indication of direction with respect to the bow an indication of direction with respect to the bow

of the boatof the boat can be indicated in one if two wayscan be indicated in one if two ways

• "red" / "green" depending in the side if the ship that the "red" / "green" depending in the side if the ship that the bearing was taken on. Red meaning the port side.  bearing was taken on. Red meaning the port side.  Green meaning the starboard side.  The bow is 0 Green meaning the starboard side.  The bow is 0 degrees and the stern is 180 degrees.degrees and the stern is 180 degrees.

• using 360 degree notation measured clockwise from using 360 degree notation measured clockwise from directly in front of the bow.  Uses three figures followed directly in front of the bow.  Uses three figures followed by the word relative.by the word relative.

are used with unstabilized radar display.  The are used with unstabilized radar display.  The direction of the ship's head must be found before direction of the ship's head must be found before relative bearings can be applied. relative bearings can be applied.

CourseCourse

is the direction in which you want is the direction in which you want your boat to proceed, usually your boat to proceed, usually designated True, Magnetic, or designated True, Magnetic, or Compass, is set using north as a Compass, is set using north as a reference point reference point

HeadingHeading

is the direction in which your boat is is the direction in which your boat is moving at any particular moment moving at any particular moment

How can you find out where you How can you find out where you are?are?

Dead Reckoning Dead Reckoning Estimated Position Estimated Position Lines of Position (LOP)Lines of Position (LOP) FixFix

Dead ReckoningDead Reckoning

It is only an approximate position. It is only an approximate position. arrived at by allowing for the course arrived at by allowing for the course

the ship is steering and ship's speed the ship is steering and ship's speed through the water, forecast from the through the water, forecast from the last known position of the ship.  last known position of the ship. 

This position is indicated on a chart This position is indicated on a chart by a + and the time arrived at. by a + and the time arrived at.

Estimated PositionEstimated Position

is calculated using all known factors that is calculated using all known factors that may be affecting the ship's progress may be affecting the ship's progress including the course steered, leeway, including the course steered, leeway, speed of the ship through the water, and speed of the ship through the water, and the set and drift of the current.  the set and drift of the current. 

It is indicated in a chart by a dot, It is indicated in a chart by a dot, indicating the actual position, surrounded indicating the actual position, surrounded by a triangle.by a triangle.

Lines of Position (LOP)Lines of Position (LOP)

is any line drawn on a chart on which is any line drawn on a chart on which the boat's position is known to lie.  the boat's position is known to lie. 

This line can be obtained visually or This line can be obtained visually or electronically.  electronically. 

Two lines are needed to determine Two lines are needed to determine the actual position, fix, of the ship. the actual position, fix, of the ship.

LOP can be obtained through a variety of LOP can be obtained through a variety of methods see p 166 of reference guide.methods see p 166 of reference guide.

position lines drawn on the chart should position lines drawn on the chart should have arrowheads to indicate how the line have arrowheads to indicate how the line if position was arrived at.if position was arrived at.

when using only two LOPs attempt to have when using only two LOPs attempt to have the LOP cross at an angle of 90 degrees to the LOP cross at an angle of 90 degrees to each other.  each other. 

errors can result if the angle is cut less errors can result if the angle is cut less than 60 degrees or greater than 120 than 60 degrees or greater than 120 degrees degrees

FixFix

is the intersection of two or more is the intersection of two or more lines of position.  lines of position. 

It is indicated on a chart by a dot It is indicated on a chart by a dot with a circle around it, the dot with a circle around it, the dot represents the actual position of the represents the actual position of the ship at the time of observation.  ship at the time of observation. 

The ideal fix has three LOPs each The ideal fix has three LOPs each cutting at 60 degrees to each other cutting at 60 degrees to each other and all intersecting at a single point and all intersecting at a single point