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Introduction to Coastal
Navigation
University of Texas Sailing Club
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Disclaimer
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I am not a certified by ASA, US Sailing, USCG or anyone else
to teach this class nor will this class count towards an ASA, US
Sailing or USCG certificate.
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The purpose of this class to inform and familiarize
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Outline
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Before sailing
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Reading charts
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Understanding symbols
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Planning a route
While sailing
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Lights & Buoys
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GPS
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Visual (line of sight) positioning
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Dead reckoning
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Basic idea of celestial navigation
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Right of way
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Google Maps
Houston
Houston Yacht Club
Kemah
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Google Earth
You try to be smart & use a satellite image…
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NOAA Chart
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Planning a course
Ship Channel
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Planning a course
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Houston Yacht Club
What additional information is given?
Google Earth
NOAA Chart
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Kemah
There’s a channel?
Google Map
NOAA Chart
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NOAA 11327 – Galveston Bay
http://www.charts.noaa.gov/InteractiveCatalog/nrnc.shtml
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Understanding Chart Symbols
Compass Rose
True (geographic
north)
Magnetic north
Correction factor
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True vs Magnetic North
Source: coastalnavigation.com/
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Understanding Chart Symbols
LIGHTS
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Fl 4s 30ft Priv = Flashing every 4
seconds 30 ft above mean tide.
Private light
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Q G 23ft “1” = Quick flashing green
23 ft above mean tide. Painted “1”.
Private light
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F R 12ft Priv = Fixed red 12 ft above
mean tide. Private light
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Fl R 6s 17ft 4M “2” Ra Ref =
Flashing red every 6 seconds 17 ft
above mean tide visible for 4 miles.
Painted “2”. Radar reflective
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G “1” Ra Ref = Green buoy painted
“1”. Radar reflective
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Understanding Chart Symbols
OBSTRUCTIONS
Visible from surface
Partly Submerged Wreck
Submerged
All sorts of fun stuff
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Understanding Chart Symbols
DEPTH
Marsh & Shallows
Dumping area from dregging
Reef
Depth in feet (US maps only)
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Plotting a Position Fix (PF)
Using several reference points to determine your location on a
chart.
+ Plotting a visual fix
At 10:40PM, You see a red
light flashing every 6
seconds at 217 degrees
and a green light flashing
every 6 seconds at 137
degrees according to your
magnetic compass. Where
are you?
2240
20 minutes later, the same
red light is at 232 degrees
and the green light is at 147
degrees. How fast are you
traveling?
You continue sailing the
same heading. 20 minutes
later, the red light is now at
250 degrees and the green
light is at 160 degrees.
What happened?
2300
2320
2320
+ Why is this
relevant?
You plan to sail the
following course from
Kemah to the Houston Yacht
Club. How do you know
when to turn (without being
glued to your GPS)?
For example:
• Sail along ship channel
until past R “2” and G “1”
• Turn to heading 030 on
your compass; pointed at
the G Radar Reflective
Mark (bad example)
• When the 6s Green is on
the beam, turn to
heading 320
• Once the 2.5s Green is
on the beam, turn to
heading 270
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A running fix
When you only recognize one object
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NOAA 13233 – Martha’s Vineyard
Below Cap Cod in Massachusetts.
(beautiful sailing, check it out at some point)
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Plotting a Running Fix (R Fix)
Using a single reference point and your assumed course to
determine your position
+ Running Fix
It’s hazy out, so you can only
see Gay Head Light. You
are sailing a course of 270
degrees magnetic at 6
knots.
• At noon, you sight gay
head at 220 degrees.
• At 12:10, it is at 180
degrees.
• At 12:20, it is at 140
degrees.
Plot your course
• Now you change course
to 180 degrees. At 12:30,
Gay Head is now at 110
degrees.
???
R Fix 1210
R Fix 1220
R Fix 1230
+ So, what?
When plotting a course, you
need at least one reference
point if you keep track of
your course
Why? This allows you to
notice currents, tides and
wind.
• What would have
happened if the course
was pushed east instead
of west?
R Fix 1210
R Fix 1220
R Fix 1230
R Fix 1230
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Distance to the Horizon
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On the ocean:
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Where d is in statute miles and h is in feet
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So if you fall in the water, you can see about a mile
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In a small boat, where your head is 3 feet off the water, two miles
To an elevated coast
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So a 10 foot dune is visible 6 miles out to sea from 3 feet above the
water
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Celestial Navigation
How stars can guide you
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Basic Idea
The moon, sun and each star is
directly overhead on some point of
the planet. Call this point A.
(technically the ephemeral point)
By measuring the angular distance
from directly over you to the object,
you know how far away from point A
you are.
It is really hard to accurately measure
direction to the object, so you
measure 2+ objects.
There is a point on the sphere where
these distances ‘intersect’. This is
your Celestial Fix.
Source: tjradcliffe.com
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In 3D
Source: wavetothewind.com/
You get a Circle of Position, but if
you zoom in, it can be approximates
as a Line of Position.
Two or more of these intersect to give
you your position on the globe.
Source: onboardintelligence.com/
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How do you
measure angles?
With a sextant
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Originally developed by Sir Isaac
Newton in the late 1600s (as an
octant)
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Refined to it’s current form in the
1757
Required accurate time keeping –
lead to the development of the
chronograph (1816)
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Plotting the fix
The more stars you measure, the
more accurate your fix becomes
(hopefully).
A lot of spherical trigonometry (or
tables in the form of the Nautical
Almanac) is needed. See me offline
if you want more information.
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How GPS works
Simply the intersection of spheres of position to give you (x,y,z)
Source: education.nationalgeographic.com/
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Navigation Lights
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Right of Way
Horns
Who yields?
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Do you need to change course?
Is a collision imminent?
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If you see green, ALL CLEAR
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If you see red, BE READY TO YIELD
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Just keep an eye on the ship – he may not see you
Determine if a collision may occur (compass bearings)
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If relative compass bearing is approaching your heading, YIELD
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If go away from your heading, ALL CLEAR
If you see white,
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If it is the stern light, ALL CLEAR
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If a mast head light, FIND THE RED OR GREEN
Make any course changes APPARENT
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Channel Markers
Keep right in virtually all marked
shipping channels in the US unless
otherwise noted.
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ALWAYS check the chart before
heading into a channel
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NEVER attempt to sail along an
active shipping channel
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CHECK tide information before
entering a narrow channel
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ENSURE your boat can go FAST
enough
Source: watercraft.ohiodnr.gov/
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Take aways
If you remember nothing else…
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Always familiarize yourself with a new body of water. What
looks sailable on Google Earth may not be so.
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http://www.charts.noaa.gov/InteractiveCatalog/nrnc.shtml
Things disappear behind the horizon!
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A swimmer can see about a mile
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A small sailboat can see about two miles (or a sand dune on a
beach 5 miles away)
A boat with its port side to you has the right of way. You have
the right of way if you see its starboard side.