In this article we are going to talk about Marine Navigation.
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Ang Page At Blogsite ng Ekspedisyong Marino ay may iba’t ibang admin na willing magshare ng kanilang ideas para makatulong at makapg-inspire sa ating mga kabaro.
Okay let’s go, paq-usapan na natin Ano ba ang Marine Navigation ?
What Is Marine Navigation
The process of directing the movements of watercraft from one point to another; the process, always present in some form when a vessel is under way and not drifting, varies with the type of craft, its mission, and its area of operation.
Other meaning…
Navigation, derived from the Latin words "navis" (meaning "ship") and "agere" (meaning "to drive") is the process of accurately determining the position and controlling the movement of a craft or vehicle along a desired course. This is accomplished by finding the navigator's position compared to known locations or patterns.
All forms of
navigation have four steps:
1.
you locate your
position
2.
you determining a
course
3.
you monitor the course
4.
and repeat
What is a navigation technique?
A navigation technique is a way to determine the navigator's
position and to set the desired course.
There are different methods of locating your position, different
plotting methods, and also different ways to determine your course.
The system of locating, plotting, and setting a course is called
a navigation method.
The most common navigation
methods are satnav, dead reckoning, and radar navigation.
§ Dead reckoning
§ Pilotage
§ Celestial navigation
§ Inertial navigation
§ Radio navigation
§ Radar navigation
§ Satellite navigation
Every method has advantages and disadvantages.
For example, dead reckoning and radar can be used to determine
your location based on just one point or object.
But you need a lot of equipment.
Celestial navigation is very reliable, but you need clear skies.
Satellite navigation is very accurate, but you need a power
source.
Celestial
navigation is one of the oldest navigation methods. The navigator
uses the celestial bodies to determine his location.
With Coastal navigation,
the navigator uses the shape of landmarks along the coast, and the direction of
the coastline.
With Inertial navigation,
you use motion sensors to calculate your new position relative to the starting
position. (This is a form of dead reckoning.)
Pilotage simply
means fixing your position with a very high frequency and is used in harbors
and restricted waters.
Radio
navigation uses radio waves to measure the direction to a radio source.
For this to work, you need radio towers all over the place. GPS is winning the
battle for sure.
Radar
navigation is mostly used to avoid collisions when you're close to
land or other ships.
Satellite navigation is the most used form of navigation nowadays. This uses multiple satellites to pinpoint your location.
You can use analog or electronic equipment to get your position and plot it.
A lot of the electronic instruments are actually just modern
replacements for the old tools: they pretty much do the same job (but faster
and better).
Locating Your Position
You can determine your position
based on your previous position, or you can look out and use pretty much any
kind of landmark, celestial body, and so on, to pinpoint where you're at.
Different
Techniques to Get Some Lines
So you need lines to know where
you are. A navigation technique is simply the way you chose to get your lines.
To get yourself some lines, there are plenty of old skool methods and modern ones as well.
§ Compass bearings - you can use a compass to get a bearing, which is the most used way for many centuries now
§ Terrestrial range -
if you find that two charted points align, this gives you a directional line
§ Radar range -
measuring the distance and direction to an object, you only need one object to
get your position accurately
§ Observing celestial
bodies - using a sextant you can get LOP from celestial bodies
§ GPS uses 24
satellites (that's 24 LOPs) to pinpoint your exact location
§ Echo sounder - not as
accurate; can only confirm the boats known position
§ Parallel indexing -
uses echo to keep a safe distance from the shoreline, rocks, and so on
§ Dead reckoning -
using your previous location and speed and course to fix a new position
§ Light dipping - using
the height of a lighthouse to measure the distance from it.
Compass bearings
Getting
a compass bearing is easy. You find a point on a chart you can see on the
horizon, and you point your compass at it. Read the angle on the compass, and
simply draw a line in that angle across the point of reference. The classic way
is three compass bearing on three widespread objects.
For
this method, you need a compass and a marine chart.
Terrestrial range
If
you don't have a compass, you can still find your direction by using two landmarks
or objects. When two charted points align with your bowsprit, for example, two
buoys, you can draw a line through them. Voila, you know your direction. This
line is called a transit.
For
this method, you need a marine chart.
Radar
Radar
is different and pretty neat because it only needs one object to get a pretty
accurate position. It can get the range and bearing from one object and plot it
directly on the chart. So it's extremely useful if you navigate let's say a
massive container ship in a crowded, tight port.
Celestial navigation
For
celestial navigation, you need a couple of tools: a nautical almanac, a marine
chronometer, and a sextant.
You
first use the almanac and chronometer to pick a subpoint. That's the point
where the planet or star is currently located above Earth. Then, you take the
sextant to measure the angle between the celestial body and the horizon. This
gives you the distance between you and the subpoint. Here's your first line of
position. A neat circle around the location of a star.
You
need a sextant, chronometer, and almanac for this method.
GPS
The
easiest and most accurate way to pinpoint a location is by using satellites. A
GPS receiver calculates the distance from multiple satellites. This gives you
some lines, that are now in the sky instead of on a map. Again, where the lines
intersect is where you are.
GPS
is extremely accurate and reliable. It can find you within half an inch, and
will only fail if there's no power source, very heavy weather, solar flares,
and so on. It will work perfectly most of the time.
It
also can't tell you which direction you're pointing towards. So you can't use
it to measure bearings.
GPS
is an American technology, and China, Russia, and Europe have their own
variants, although they are not as widely supported.
You
need at least a GPS receiver, plus a marine chart or a chartplotter.
Echo Sounder
An
echo sounder is a sonar that's used to determine the water depth. It uses sound
waves and measures the delay of the reflections. This tells the distance to the
bottom.
Echo
sounding can be used to estimate a location but it's not very accurate. You
also need some sort of bearing. Then check the chart and your current depth.
Check at what point your depth and the bearing intersect.
For
this method, you need a sonar device, fishfinder, or MFD (multi functional
display).
Parallel indexing
If
you're sailing in a port or bay, there are lots of other vessels and objects to
avoid. So you want to stay on course accurately. To do this, you need to
monitor your position very carefully. If you want to avoid to have to plot your
position every minute, you could use parallel indexing to stay on course.
You
need a radar for this method.
Dead reckoning
You can also measure
the distance from your old position. For this, you need your course and speed.
This is called dead
reckoning. It's the same principle. Your old position is the
'object'. Your course is the angle (bearing), and your speed is the distance,
giving you a line of position.
You
need an inertial navigator for this method
Light dipping
This method isn't
used a lot, but it can be handy. We check when the top of the lighthouse
appears on the horizon. If we know the height of the lighthouse, and our eye
height, you can calculate how far away we are.
You
need a sextant and nautical almanac for this method.
List of Marine Navigation
Equipment
§ Gyro compass
§ Magnetic compass
§ Fluxgate compass
§ GPS receiver
§ Compass Deviation
Card
§ Radar
§ Autopilot
§ ARPA
§ Automatic Tracking
Aid
§ Speed & Distance
Log Device
§ Echo Sounder
§ Electronic Charts and
Chartplotters
§ Weather Satellite
Systems
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