nautical charts can anyone explain the purpose of a nautical chart?
DESCRIPTION
I. Purpose of Nautical Charts Nautical charts are different from maps in that they specifically depict water areas, while maps concentrate on land area, roads, landmarks, etc. Land areas and features on charts are sketchy and are noted only for their interest to the boater. Unlike maps, the nautical chart conveys much information specifically designed to assist in safely navigating the area that the chart covers Nautical charts are different from maps in that they specifically depict water areas. Land areas and features on charts are sketchy, meaning that there is not much detail/it is just a rough outline, and are noted only for their interest to the boater Nautical charts are specifically designed to assist in safely navigating the areaTRANSCRIPT
NAUTICAL CHARTS Can anyone explain the purpose of a Nautical
Chart?
(let them answer) A chart onboard allows you to compare what you
are seeing with what you should be seeing and can help you keep
your bearings. I. Purpose of Nautical Charts
Nautical charts are different from maps in that they specifically
depict water areas, while maps concentrate on land area, roads,
landmarks, etc. Land areas and features on charts are sketchy and
are noted only for their interest to the boater. Unlike maps, the
nautical chart conveys much information specifically designed to
assist in safely navigating the area that the chart covers Nautical
charts are different from maps in that they specifically depict
water areas. Land areas and features on charts are sketchy, meaning
that there is not much detail/it is just a rough outline, and are
noted only for their interest to the boater Nautical charts are
specifically designed to assist in safely navigating the area II.
How to use a nautical chart for a boating trip
Study your chart thoroughly. Look at the position from which you
will start and visually follow along the course you wish to take.
Look for "notes" - water depths, obstructions (especially under
water), bridges, power lines or any other unusual items that may be
a hazard to your progress. Look for visual objects featured on your
chart that you should be able to observe and identify to confirm
your position. When utilizing a Nautical Chart, even for reference
you want to: Study the area that your chart covers or the area you
intend to be at What are some of the things you should look for?
Yes you want to pay attention to notes, water depths, obstructions
or any other items that my be a hazard Look for visual objects on
your chat that you should be able to observe and identify to
confirm your position. III. Reading a Nautical Chart
A.Look for the chart title at the top right of the chart. Now to
use a Nautical Chart you have to understand some basic features: a.
Every chart has a title. It will be larger than the rest of the
print and can also be found by the chart number in the margin III.
Reading a Nautical Chart
B.CHART ORIENTATION TRUE NORTH is at the top of the chart. EAST is
at the right-hand side of the chart. WEST is at the left-hand side
of the chart. SOUTH is at the bottom of the chart. Charts are
always oriented with True North at the top, East on the right hand
side of the chart, West on the left hand side of the chart and
South at the bottom of the chart. III. Reading a Nautical
Chart
THE COMPASS ROSE MAGNETIC NORTH TRUE NORTH Magnetic North moves
over time.For the SF Bay, it is currently about 15 East of North.
True North is the point around which the earth rotates. Every Chart
has a compass rose. The compass rose is used to get bearings from
landmarks, or buoys The star on the Compass Rose points to True
North. Where the North pole actually is The inner circle projects
Magnetic North. Which shows the pull from earths magnetic field
III. Reading a Nautical Chart
C.SOUNDINGS Soundings are in meters, feet, or fathoms (6 feet per 1
fathom) Sounding Numbers reflect the depth of the water Map Colors
- shallow water is tinted a darker blue and deeper water is a
lighter blue and white. 1. All chart measure the depth of the water
in meters, feet, or fathoms.A fathom is a measurement that 1 fathom
equals 6 feet and is only used in water depths. 2. Each chart will
show the unit of measurement in the margin 3. No chart will have
more than one unit of measurement for soundings Soundings As you
can see here the white area depicts an area with deeper water depth
(point out a couple water depths feet) Then the blue shows the area
that is not as deep and could pose a hazard to normal boating
traffic. (point out a couple water depthsfeet) You can see a
channel that the larger vessels have to follow. NAUTICAL CHARTS
SOUNDINGS CONT.
Depths of water are the mean depth for that area. Water depth can
be affected by the storms, the moon, wrecks, and shoaling
(sandbanks), and winds It is important to know that soundings are
only the average depth for that area, which means that depths can
be higher or lower than the printed depth What are some factors
that would cause the water depth to change? (if they get stuck here
is a hint, think about tides!) 2. The reason they are only an
average depth if because water depth can be affected by storms,
wrecks, shoaling, or general daily tides. Note: For any particular
location, the height and fluctuation of tides depends to varying
degrees on the location of the Sun and the Moon, and to the details
of the shape of the beach, coastline, coastline depth and
prevailing ocean currents D.Other Symbols There are 39 different
types of bottom for the ocean floor. If an areas bottom is knownit
will be displayed on the chart M = Mud The type of ocean floor is
important information for fisherman, wade fishers, marine
biologist, and vessels anchoring in that area There are 39
different types of ocean floors. Harbor charts will annotate what
type of ocean floor was observed In this example the M means that
the ocean floor is made up of mud. Does anyone know what type of
bottom comprises a good part of San Francisco Bay?(mud and silt)
LIGHTS AND AIDS TO NAVIGATION (ATON)
D.Other Symbols LIGHTS AND AIDS TO NAVIGATION (ATON) There are
numerous different types and configurations of aids to navigations
(ATONs). In fact way too many and way to complicated to go over.
Can anyone tell me what this is and what it is for? (buoys can be
used to mark channels, bays, wrecks and sometimes have horns or
whistles which aid mariners in navigating during foggy conditions.)
E.Latitude & Longitude Points of latitude and longitude are
plotted like X, Y coordinates Latitude = X coordinate Longitude = Y
coordinate (Latitude, Longitude) Latitude and Longitude are
measured in degrees. One degree is broken into 60 minutes Here is a
graph that everyone is familiar with right? And The graph is made
up 4 quadrants just as the earth is split up into 4 quadrants. E.
Latitude & Longitude = 1 Minute = 1 Minute LARGE SCALE SMALL
SCALE
As you can see with the small scale chart each block is 1 minute
But with the Large scale chart each minute is broken down to
seconds. LARGE SCALE SMALL SCALE Can you find the coordinates for
the red X?
Latitude = 39 57 min N Longitude = 24 53 E Now looking at Latitude
and Longitude- Charts are in Degrees, minutes, and seconds. Each
charts will be labeled with a number and a degree symbol indicating
the degrees lat or long. As shown here (point) with 40 degrees
North Thenit will be further broken down, between each degree, with
numbers and a minute symbol. As shown here (point) with 55 minutes
North. Note that there are 60 minutes in 1 degree. It is further
broken down to seconds, which there are 60 seconds in a minute
Coordinates: (39 57 min N, 24 53 min E) Fishing vessel northern
belle
Emergencies Nautical Charts are not only used for navigation, but
for emergency situations as well.Knowing your location allows
responders to get to you quicker.In fact, one of the first things
the Coast Guard does is plot the position to get a visual reference
of the person in distress, then they dispatch resources to that
location to search. The video linked from below is an example of a
rescue operation that started with a distress call in which the
boat captain provides his position as a lat & long coordinate.
(after audio) This is an example of a Search and Rescue case,
something the Coast Guard does daily.This shows that Nautical
Charts are not only used for navigation, but for emergency
situations as well.Knowing your location allows responders to get
to you quicker.In fact, one of the first things we do is plot the
position to get a visual reference of the person in distress, then
we immediately dispatch resources to that location to search. Does
anyone know what the numbers were that the Captain called out?
Fishing vessel northern belle