Navigation and navigation. . .
Measuring the direction and distance of the distance at sea, this allows us to measure the old log in terms of speed has long been replaced by more complex mechanical and electronic equipment.
The oldest is the Walker log.
This is a torpedo.
On the length of a woven line, a spinner in the shape of a few inches long is dragged behind the boat.
When it moves in the water, the spiral fin on the torpedo will make it rotate and twist the line. The on-
The plate end of the line is connected to the back of the log instrument, where it rotates the shaft connected to the deceleration gear box.
This in turn moves hands on a series of dials, like the old-fashioned gas meter, directly reading the distance the spinner moves in the water.
The advantage of Walker log is its rugged simplicity and the convenience of removing weeds or debris from pinner.
Its disadvantage is that its display must be installed at the back of the ship;
Log line (
Usually 30 or 60 feet in length
Must be streamed before the log can be used and restored before entering the port;
It tends to be lower-
Read at a very low speed;
At a speed of about ten knots, the spinner tends to jump out of the water and slide along the water.
There are clear techniques for streaming and restoring mechanical tracking logs designed to reduce the risk of line winding.
To stream logs, attach on-first-
Display the plate end of the hook on the back of the unit.
Then, keep the spinner in hand and feed all the lines out to form a long U-
Before throwing the spinner outside the ship, tilt the shaped ring back away from the side of the ring.
Some owners like to stick to the back of the display unit for a few seconds, just to absorb the grip when the load reaches the line.
Speed is essential when restoring logs, especially if the ship moves fast.
Release the inside end of the board from the hook on the back of the display and put it outside the ship so that when you pull the log line, it can be tracked back to the ship.
Then take the spinner and line up and wrap it around as you walk.
Trailing rear lines like this can unlock any kinks.
The electric trailer log is on the surface similar to the Walker log because it uses the spinner on the long line to mop the rear of the boat.
In this case, however, the spinner is divided into two parts, and the "log line" is the cable.
The front part of the spinner is connected to the cable and only the rear part can be rotated freely.
When it does this, the electronic sensor on the front will make and disconnect the circuit, so on-
The board display unit receives short pulse power each time the spinner rotates.
These pulses are counted electronically and displayed in digital form for speed and distance operation.
The advantages and disadvantages of this type of log are very similar to the mechanical Walker log, except that it relies on the power of the internal dry battery, in return, it allows the display unit to be installed almost anywhere on board, and because the line itself is not distorted, it is quite easy to stream and recover. Hull-
Mounted impeller logsOn cruise ship, Hull-
The installation logs are by far the most popular type, although in principle they are very similar to the electrical tracking logs: the rotating impeller sends a pulse stream to the display unit installed near the cockpit or chart. The impeller -
This can be a miniature version of the trailing log spinner, or a paddle wheel about inches in diameter-
Mounted in an accessory called a sensor that can highlight the bottom of the boat or hang under the beam.
The disadvantage of this system is that the impeller so close to the hull is affected by the flow of water around the hull, and the withdrawal of sensors at sea to remove weeds or debris is difficult and potentially dangerous. The reason in-
Hull logs are so popular, mainly to facilitate the flow and recovery of 30 feet or more log lines at the beginning and end of each article.
Other logsAt with the highest price and complexity are several alternative ways to measure the speed in water: induction logs are based on the same principle as generators and motors: If you move the magnetic field to a conductor, the current will be generated.
In this case, the conductor is seawater and the magnetic field is generated by the sensor.
When the sensor moves in the water, a small current is measured through the sensor.
The sonic log uses an accurate measurement of the sound speed between two previously installed sensors.
Each sensor makes a continuous click, and the human ear cannot hear it, while listening to the Click from another sensor.
When the ship is traveling, the water passes through the hull's motion to slow down the clicking sound of the forward, while speeding up the backward.
The instrument accurately measures the time spent on each click trip, compares them, converts the results into a speed display through the water, and calculates the distance from this.
Another type of acoustic logging uses advanced echo depth detector technology to measure the speed at which plankton and debris pass through their sensors.
The biggest advantage of these three types is that they are more than ordinary in-
Hull logs, when turbulence or bubbles make the impeller logs unreliable, they can continue to work at very high speeds or in harsh marine conditions.
Calibration of logsNo logs can be relied on to ensure 100 accuracy.
This is especially true for Hull mounting logs because-
In addition to the inherent inaccuracies of the instrument itself --
Dirt increases as the season goes on, which means the boat is dragging
A layer of water is thickened along it, so the flow through the impeller will be slower than the boat passing through the water.
Instead, around certain parts of the hull, such as next to the keel of the sailing boat or near the propeller of the motor boat, the flow of water may actually accelerate, resulting in a log overflowread.
If you know the error, you can always allow the error to occur, and most electronic logs have a calibration facility that can be adjusted based on these changes.
Finding and correcting log errors if necessary is called calibration.
In principle, it includes measuring the time required to cover a known distance, using it to calculate the real speed, and comparing it to the speed indicated by the log. Any accurately-
Known distances can be used, although the best distance is undoubtedly the measured distance set specifically for this purpose.
They are composed of two (
For transfer piles, accurately mark the beginning and end of
Measure the distance and display it on the appropriate chart.
The process of measuring the distance of steering coverage is also shown.
Before passing through the first transit line, park the ship on the route and travel at a steady speed;
Make a note of the time you go through the starting point, keep the route and speed, regardless of the wind or TIDE, until you cross the finish line and take note of the time spent.
Note that an actual log read is performed every 15 seconds, so that you can calculate the average log speed of the entire run.
Since completely stationary water is rare, it is important to repeat the process in the opposite direction.
After finding the speed in both directions, by taking the average value, adding the two speeds and dividing them by two, the speed through water can be calculated.
More accurate results can be obtained by running four to six times, but this can be a very time-
The consumption process, especially at all speeds, the log error is not necessarily the same, so the calibration operation needs to be carried out in different speed ranges and checked repeatedly after adjusting the log.
A common mistake is to calculate the average time spent and divide the distance by this.
The result is always to underestimate the speed of the ship, as it certainly takes longer in the "slow" direction than in the "fast" direction.
Some large charts (harbour plans)
There is a clear distance scale-
Like you found on the road atlas.
It is usually printed near the bottom edge.
But this is not always the case on smaller-scale charts for coastal and maritime navigation, it is impractical to provide such a scale, as the scale of the chart varies slightly from top to bottom.
However, by definition, a sea is a minute of latitude, so the latitude scale on both sides of the chart constitutes a distance scale.
The slight difference between the sea and the international sea is so small that it can be ignored for normal sailing: on small scale charts, it is important that the distortion caused by the Mercato projection, this means that the distance must be measured at latitude using the distance.
The warp scale at the top and bottom edges of the chart is useless as a distance scale.
It is relatively rare to find yourself facing the work of measuring distance in the complete North
So we need some way to transfer the distance between any two points on the chart to the latitude scale.
Partitions are a tool for this work.
For classroom navigation, the seperators used in technical drawings are completely sufficient, and their sharp needle points give a reassuring sense of precision, but for actual navigation, the traditional bow divider has a great advantage in opening and closing the bow with one hand and squeezing the legs to close them
Sometimes it is necessary to draw arcs measuring the radius on the chart, for which it is useful to have a drawing compass.
Again, as long as it is large enough, the type used for technical drawings can be used, but usually it is better to use larger and less complex versions for marine navigation.
Measurement direction of compass and sea direction using compass
Essentially an instrument that points to the north, regardless of the movement of the ship around it, it continues to point to the north.
In fact, most yachts have at least two compasses.
First, the steering compass is relatively large and fixed on board to measure the course.
The other, which is usually smaller and easy to carry, is used to measure the direction of a distant object and is therefore called a handheld compass.
Sometimes a compass can do both: on many ships and several large yachts, an attachment called pelorus allows the steering compass to be used to withstand bearings, the hand-held compass on a very small clip holder can be used as a steering compass.
There are many ways to make an instrument that points in one direction, including the gyro and the so-called "ring laser gyro", but although these have their advantages, they are too complicated, so, this is very expensive for yachts.
The vast majority of the yacht compass depends on magnetic properties, in which direct development can be seen from instruments that may have been used thousands of years ago.
The compass takes advantage of the fact that the Earth has a magnetic field, which is like a giant bar magnet embedded in its core and aligned with its north --South axis.
Any magnet that can swing freely will be aligned with the Earth's magnetic field.
This effect is particularly evident in small flat compasses used for directional movement and walking on land, in which a straight needle-
Just like the magnet shows the north directly.
In the marine compasses, several of these magnets, or a single magnet of a ring, are mounted under a circular "card" with a scale or compass point.
The whole thing is suspended in a bowl filled with a mixture of water and alcohol, which slows down the movement of the card and reduces the swing caused by the tilt and roll of the boat.
The compasses used for fast-moving vessels have greater damping than the compasses used for sailing boats;
The rapid impact of the boat is enough to make the card of the sailing compass rotate continuously.
Steering combination on the forward steering compassand-
The tail line of the ship is marked by a line or pointer on the Compass Bowl, called the Luber line, which can read the current course of the ship from the card, so it is obviously important to install the compass, in this way, the Lubo line can be accurately aligned or parallel to the center line of the ship.
Many compasses have complementary lugs of 45 ° and 90 ° offset on each side, mainly used in cases such as rudder handles
The helmsman may look at the rigged vessel of the compass from one side or the other.
Of course, there are also variations that are suitable for specific applications.
On many small and medium sailboats, the cockpit space is large, and the compass is set on the rear partition of the superstructure so that the rear edge of the card can be seen, rather than its upper surface.
The compass for this installation has the rear lub line and the degree marked below
Turn the edge of the card around
More extreme changes are occasionally found in the compasses used in the steel process, and their structure effectively shields the compasses in the Earth's magnetic field.
By installing the compass above the hull as high as possible, this problem can be reduced, so a compass that can be installed on the roof of the cab has been generated by setting the mirror or prism, the helmsman can effectively look up at the bottom of the compass card.
Grid compasses are mainly used for aircraft navigation, and after World War II, grid compasses are becoming more and more popular when many ships are installed from the Army's remaining stores!
Claiming that they are easier to drive by keeping their popularity for at least 20 years and producing several stewing versions.
The Grid Compass has a card with a particularly prominent north on ittopped bowl.
The top of the bowl is a transparent cover marked with parallel line mesh with a certain scale on the edge.
The required course is set by rotating the lid, the helmsman then manipulates to keep--.
The mark on the card is aligned with the grid.
The handheld compass is basically a small portable version of the steering compass, equipped with some form of aiming device that allows it to be arranged precisely on objects in the distance.
They can be subdivided into two groups: those intended to be used at arm length, usually with handles;
Things that are intended to be close to the eyes, usually with a neck strap.
Which is the best, which is largely a matter of personal preference, but anyone who uses glasses or hearing aids should go and buy arms --
Because even a small piece of black metal like a glasses hinge, if it is only a few inches away from the compass, it will cause a compass error.
The observation arrangements are different.
For example, the classic Sestrel Radiant has a prism mounted above the bowl with V-
The shape gap at the top.
When the compass is raised at arm length and eye height, the Luber line and Compass Card can be seen in the prism.
To shoot the orientation of a distant object, align the "target" with the cut, rotate the compass until the lubber line appears in the prism directly below the target, and then read the bearing
Another common arrangement is that there are two attractions at the top of the bowl, such as the front and rear view of the gun, and the edges --
Read the compass card. Close-to-the-
The eye gauge does not have such an obvious observation arrangement: instead, they have a small prism installed on the top, and its optical system is arranged in such a way that when you see a landmark on the top of the compass, its orientation appears in the Prism immediately below.
The new compass is rapidly gaining popularity.
Unlike the traditional "swing card" Compass, the magnetic door compass does not move parts, but uses an electronic device to detect the Earth's magnetic field and displays this information on a certain display.
The magnetic door depends on the phenomenon of induction.
Used in the ignition line of Transformers and gasoline engines.
If you pass the current through a coil wound around a suitable metal core, the core becomes a magnet.
Which end is the Arctic, which end is the south, depending on the direction of the current in the wire, so if you apply AC to the wire, each time the current reverses, the north and south poles of the core change will occur.
If you wrap a second wire around the entire assembly
The reverse magnetic field generates current in the secondary winding.
In the flux gate, there are two cores side by side, and their primary winding receives alternating current from the same power supply, but in the opposite direction.
This means that in a magnetic "clean" environment (
No external magnetic field influence)
The inductive magnetic properties in both cores are equal and opposite, so they offset each other and do not generate current at all in the secondary winding surrounding them.
The presence of an external magnetic field disrupts the balance, and each time the primary current is reversed, the current in the secondary winding increases briefly.
This effect is most obvious if the two cores are parallel to the external magnetic field.
In a practical magnetic door compass, there are several magnetic doors in a circle.
By comparing the induced voltage in various secondary windings, it is possible to infer the position of the North relative to the magnetic ringgates.
At present, the most commonly used use of this technology is to provide heading information for other electronic equipment such as autopilot or radar, but it can also be used to provide steering display for the helmsman, or as the heart of an electronic compass.
In addition to the fact that flux gate compasses can be easily connected to other navigation electronic devices, their greatest advantage is that automatic correction devices can be installed, since sensors and displays are often separate, so the sensor can be installed anywhere on the ship, away from the effects of the distorted magnetic field.
Fluxgate handheld compasses also feature the ability to "store" the title to save the navigator time to remember the title.
Their main drawback is that a very large error may occur if the flux gate ring is not fully maintained.
There is an electronic solution to this problem, but the fact remains that a compass without moving parts actually requires a more complex frame arrangement than a swing card.