course recorder working principle

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Principle & Working of a Course Recorder

Course Recorder Is Used for record Keeping.Record keeping is very important.  It provides evidence of the courses steering by the ship, this evidence is vital if for some reason as enquiry is needed, for example after an accident.

Course Recorder: This is a graphic record keeping device which can record all gyro courses steered by the ship throughout the voyage.  It has a built-in clock which keeps time accurately (on older ships this clock is a winding type but on modern ships it is usually electrical or quartz).  This instrument is fitted on the ship’s bridge and is a legal requirement.

Need for a Course Recorder

• It is one of the most important sources of evidence regarding the courses steered by the ship in case of an accident like a collision or grounding.
• A minute to a minute record of course and time cannot be maintained manually as weather, yawing, and fluctuations in steering affect course steered. Hence the need to have an automatic recorder.
• It records the correct time of even small alterations.
• The recorded graph indicates whether the vessel is steering a steady course or if there is too much wandering either due to the weather or the compass itself. If it is due to the weather then adjustments can be made on the autopilot.

Two inputs are required for a Course Recorder to function

• The gyro compass repeater connected to the course recorder gives signals to control the spirally grooved drum, which moves the course and zone stylus.
• The clock connected to the paper feed roller controls the speed at which the paper is pulled under the stylus so the time graduations on the recording paper move at the correct speed.

Let us take a look at the Course Recorder paper

The course recorder paper looks like a graph paper with vertical graduations as the time scale and horizontal graduations as the course scale.  It may either be a roll of paper or like a set of continuous joined sheets of paper like the perforated feed sheets of a printer.  It has three sections:

• The time scale (the vertical scale) may be found either on the extreme right or left side of the paper (depends on the manufacturer). Usually, the graduations mark 10 minute intervals.  This time scale is used to set the course recorder paper to show the correct UTC or GMT prior to starting.
• The course section which occupies the middle portion of the paper. This part is graduated for 90º as follows:

000                10        20        30        40………80     90

180                170     160     150       140…….100    90

180                190     200     210       220…….260   270

360                350     340     330       320…   ..280  270

The scale is sufficiently magnified to be able to read the course steered to the nearest degree.  For example, if the recorder shows a line on 320º, there should be some way of knowing if the course steered was 320º or 220º or 140º or 40º.  This ambiguity is taken care of in the zone section.

• The zone section is found on the side opposite the time scale. So if the time scale is on the right-hand side of the paper then the zone section is found on the left-hand side and vice versa. This zone consists of four columns, each column corresponding to one quadrants  0-90, 90-180, 180-270 & 270-360.

Depending on which column the zone pen is in, the appropriate scale can be read on the course section.

Here is a sample record of the course recorder.  Four cases are illustrated.

• Case A: Referring first to the zone column, at the bottom and reading upward, the chart shows that the heading was in the first quadrant (0º – 90º) until 12:55 PM. It then swung into the second quadrant (90º – 180º). Sighting across the record at 12:50 PM and reading the first quadrant figures, the course is seen to be 74º.  Again sighting across at 1:00 PM, the course is read in the second quadrant figures as 109º.  (The course change from 74º to 109º is shown on the small diagram superimposed on the middle of the record.)  
• Case B: Again referring first to the zone column, the heading is shown to start in the second quadrant, then to swing to the third quadrant for only a brief period, then back again to the second quadrant. Consequently, the initial course is read as 168º, and the final course as 159º.  The re-entrant part of the plot is read in the third quadrant and shows the maximum point in the swing to be 182º.
• Case C: The zone column shows the initial heading to be in the fourth quadrant and therefore to be read as 342º. The final heading is in the first quadrant and consequently is 24º.
• Case D: The zone column indicated a swing from the second to the fourth quadrant. Therefore the initial heading was 172º and the final heading 277º.  The gradual upward sweep of the trace indicates a slow but fairly constant change of the ship’s heading.

What other markings should you make  on the course recorder paper?

• Before the start of the voyage, the date, time voyage commenced, the voyage number, and the port of departure.  
• Every noon your position should be written on the paper.  
• During port arrival and departure – the times of pilot boarding and departure times, thus keeping a record of pilotage time and courses steered.  
• Any alterations of course at sea and the time of alterations. This will also give an indication if the course recorder clock is functioning well or not.  
• Weather conditions, wind, state of the sea and swell whether head swell or beam swell may be recorded on the chart. Weather and rudder adjustments on the steering may also be recorded.  
• The recorder clock should be checked for error against correct GMT and any error should be noted. In case the error is large, it should be corrected by adjusting the paper.  If the error in the clock is very large and requires frequent adjustments – it is better to get the course recorder serviced by authorized technicians as frequent adjustment of the paper may give wrong recordings and this will not be acceptable.

The Stylus or the Recording Pen

The stylus may be of two types:

• Ink pens: This was found on the older course recorders. These pens had to be filled with slow drying ink once a week.
• Conducting wires: Modern course recorders are fitted with pens which are simply conducting wires which make a black mark on the chart paper touching the back metal plate. They contain no ink.  

The course recorder usually has two pens one for the zone section and one for the course section.  These pens are hinged so that they can be raised when changing the recording paper.

How the course recorder works

The operation of a course recorder is straightforward. Read this section and study the photograph then examine the course recorder on the bridge of your ship.  

Refer to the figure (left) on the course recorder:

The drum consists of two sections; one with a continuous zig-zag groove cut in it going around the drum (B) and the other with a continuous stepped groove running around the drum (C).  There is also a horizontal guide bar with a slit in it through which the pens are fitted and run.

The gyro signal (giving the ship’s heading) is amplified and fed into the servo motor (A).  This signal rotates the servo motor and turns the drum in the direction indicated.  The course pen moves along the zig-zag groove across the paper.   In the figure, if the drum turns clockwise, the course pen will move to the left and vice versa.  The zone pen will stay in its present groove (180 – 270) until the course has reached the junction .  If the drum turns any more clockwise, the course pen will begin to move to the right and the zone pen will slip into the next zone (270 – 360).

The course being steered can be read by simply checking where the zone pen is (for example 180-270).  Then we use that scale on the course section of the paper to read the course being steered as indicated by the course pen.

Changing Recording Paper

As mentioned earlier the recording paper could either be a paper roll or continuous feed sheets (depending on the manufacturer).  Instructions on how to change the recording paper are given in the operation manual of the instrument.

Changing the paper on a typical course recorder is described here.  

• Open the paper holders to both sides. Open the base plate toward the operator and place the recording paper in the chart receiving box.
• Let the paper pass between the rollers located on the side of the upper feed drum and let the paper pass over the upper feed drum from the rear to the front.
• Fit the holes of the two edges of the paper uniformly on the pins of the feed drum and be sure to attach the four lines which indicate quadrants so that they come on the left side. At this time both the course and zone pens should be raised.

After sufficiently pulling out the paper so that the feed drums turn smoothly, close the base plate.  Insert the paper in the lower feed drum from the operator’s side toward the inner side.  When the pins of the feed drum are in the holes of the recording paper, feed out the paper by slowly turning the chart adjusting gear toward the operator.  When the recording paper on the base plate shows no slack, press the paper with the paper holders at the two sides.  This completes the task.

Removing recording paper

When removing the recording paper, turn all switches to OFF; raise the pens. Slowly turn the chart adjusting gear toward the operator until the remaining recording paper is fed.  Then, remove the recording paper.

• To remove a partially recorded recording paper, cut the paper. Turn the chart adjusting gear to feed out the paper and then take it out.

Starting and Stopping a Course Recorder

Different manufacturer’s stipulate different methods of starting and stopping their course recorders and these should be strictly followed.  One method is given below:

• Attach a new roll of course recording paper, if necessary.
• Lower both the zone and course pen with the pen-raise knob.
• Ensure the time on the recording paper (where the course pen touches the paper) matches the correct GMT.

To match the two times – turn the power switch to OFF.  Slowly turn the chart adjusting gear so that the recording paper comes to the right point, taking care not to let the recording paper slacken.  Then, turn ON the power switch.

• To match the course pen and the Master compass:
• Turn OFF the repeater switch.
• Turn the indication tuning gear to bring the zone pen in the same quadrant as the ship’s course and, at the same time, match the course pen to the proper course on the recording paper.
• After completion of the above operations, ensure that the recording paper is properly set on the pins of the paper feed drums and that the drums rotate freely.

Switch on the power switch after adjusting the time and now the recorder is recording the courses steered.

Stopping the recorder:  

• Turn off the repeater switch to stop the servo motor.
• Turn off the main power.
• Raise both the zone and course pens.

Care / Checks and Maintenance of the Course Recorder

The course recorder is an instrument that requires almost no maintenance.  However, the manufacturer’s instructions should be followed.  The following checks should be carried out when operating the course recorder:

• The course recorder should be checked every watch by the officer, to see that the pens are recording the correct course as compared to the master gyro and the recorder is keeping the correct time. If there is any error it should be reset as mentioned earlier otherwise the record obtained would be useless.
• When the ship passes any important landmark or alters course it should be recorded on the course recorder paper.
• A red line indicates the paper roll or feed sheets is close it the end. This shows either at the corner of the recorder paper or across the paper. When this is seen, a new roll of paper should be made ready for attaching to the recorder so that not much recording data is lost.
• When the ship arrives at a port, the recorder should be stopped and the clock should be switched off. The pens should be kept in raised position.
• Frequently check that the paper is fed to the recorder properly and is not getting damaged near the guide pin or at the rollers.  

Off Course Alarm in General

• The off-course alarm normally is part of the autopilot unit.  
• The alarm is provided to alert the watchkeeper if there is a deviation from the course set when the ship is being steered by the auto-pilot.  
• It consists of an audible and visual alarm.  
• A control is provided in the autopilot unit to set the maximum allowed heading deviation from the desired course before the off course alarm goes off. The setting span is normally from 2 degrees to 15 degrees.  
• The maximum permissible deviation from the desired course should be decided to take into account the prevailing weather, proximity of navigational hazards and traffic conditions.  
• There should be a routine to test the off course alarm daily while at sea. In addition, this should be tested prior departure from a port.  
• Some ships may also have a magnetic off course alarm.

Please note:

When the ship is fitted with an off course alarm for the magnetic compass, care should be taken to adjust this after every course alteration as the error on the magnetic compass may vary from course to course.  Also, it should be noted that magnetic compasses tend to sway quite a bit with the ship’s movement and this has to be allowed for when setting the span.  Weather condition also has to be taken into account.

It is the primary responsibility of the duty officer to check that the off course alarm is set properly.  Any off course alarm heard should not be treated lightly by silencing the alarm.  The cause should be thoroughly investigated – all courses checked, errors of the compass taken, a position of the vessel plotted to ensure that all is well.

Any false alarm should be immediately brought to the notice of the master and any fault rectified.  

UNDER NO CIRCUMSTANCES SHOULD THIS ALARM BE SILENCED OR KEPT OFF.

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Course Recorder

It records the Gyro course steered by the vessel continuously against a time scale.

The record is considered as useful and vital evidence in case of any accident.

The equipment is set at the commencement of a voyage with correct time and then switched on for operation.

Once set, the course recorder records the Gyro course steered on a specially designed paper throughout the voyage.

The course recorder receives a feed from the ships Master Gyro Compass

The recording paper is a specially formatted thermal paper hence an inkless stylus is used to mark the course steered,

Paper is fed by a paper feed DC motor.

Working of a Course Recorder

The styli (plural of stylus)

There are two styli, one for marking the quadrant of the course and the other for marking the course in that quadrant.

They are inkless and make impression on the thermal paper,

Both styli are mounted on a shaft and driven by a drum with groove acting as a guide.

The Recording Paper

The horizontal axis of the recording paper is divided in three sections:

Quadrant section

Since the same scale is used for all four quadrants, there must be a way to identify the correct quadrant.

The quadrant section of the paper helps us to remove this ambiguity.

The quadrant section is on the left side of the paper and is divided in four columns and marked as:

0-90; 90-180; 180-270; 270-360

The second stylus draws in this section and shows the quadrant of the course.

Course Section

The course section occupies the centre of the paper and is graduated from left to right for quadrantal course as below:

00,10,20……………………080,090

180,170……………………..100,090

180,190……………………..260,270

360,350……………………..280,170

The scale is sufficiently magnified to read the course to the nearest degree.

One of the two styli marks the course on this part of the paper to show the course being steered.

The vertical axis is the time scale. Horizontal lines are drawn for every 10 minutes. The whole hours are printed with the 20 th and 40 th minutes.

At the beginning of the voyage this must be set for the UTC.

Although, few ships prefer to set the course recorder to Ships Time.

The gyro signal for the ships heading is amplified and fed to the synchro-motor which rotates the drum.

The drum consists of two sections:

• One with a continuous zigzag groove cut in it going round the drum.
• The other with a continuous a stepped groove going around the drum.

When the drum rotates the course stylus moves along the zigzag groove across the paper.

If the drum rotates clock-wise the stylus will travel from right to left and vice versa.

The quadrant stylus will remain in the present quadrant (90-180) till the time the course stylus has approached any end of the paper and the drum continuing to turn in the same direction.

The course being steered can be read simple by first checking the quadrant section and then checking the course section.

Paper roll is driven by DC motor in synch, with UTC.

2 nd Officer checks for Course Recorder

• The OOE must check the styli are recording the correct course and the time indicated is correct.
• OOW should mark important event on the course recorder
• When carrying out checks and test as part of daily checks or prior arrival/departure checks
• When passing important landmark
• Noon positions
• Before any vessel movement, even shifting inside the port, it must be switched on and set for the correct course and time.

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What is a Course Recorder?

Course recorder is navigational equipment for automatically recording the course of the vessel over a period of time. The record is done on the continuous paper belt. The recorder is operated from  a gyrocompass or a remote magnetic compass.

Features of the course recorder are as follows.

• No lubrication is required on account of a simple mechanism.
• Every watch the officer is to check whether the correct course is being recorded & pens are full of ink.
• The course recorder clock is always to be set to GMT.
• To be switched off in port.
• Date, time & place are important. Start-up should be noted.
• Should not run out of paper. 

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SEAMAN LIFE

OPERATION AND MAINTENANCE OF COURSE RECORDER!!!

1. COURSE RECORDER?  

• The course recorder automatically records the course of the ship on recording paper. The ship’s course is sent into the ship’s course recorder from the master compass of the ship.
• The recording paper has a time scale. It is driven by a paper feed motor.
• When the voyage is completed, remove the recording paper and file it for reference.
• This recorder, together with the record of the log, serves as an effective record of a voyage with many variations.  

2. OPERATION OF COURSE RECORDER

1) starting.

• When necessary, attach a new roll of recording paper.
• Lower the pen with the pen raise knob.
• Be sure to match the time of the recording paper to the ship’s time.
• To match the two times, turn the power switch to OFF, until the time on the recording paper comes to the right point, slowly turn the chart adjusting gear toward the operator, taking care not to let the recording paper slacken. Then, turn on the power switch.
• To turn the course pen and master compass, after turning off the repeater switch, slowly turn the indication turning gear to bring the zone pen in the same quadrant as ship’s course and, at the same time, match the course pen to the proper course on the recording paper. If the recorder is not turned with the master compass, the course is recorded with a definite error.
• With the above operations, the course recorder attains the recording condition. However, confirm that the recording paper is properly set on the pins of the paper feed drums and that the recording paper which has been fed is properly folded.

2)   STOPPING

• Since repeater motor stops when the power supply of the master compass is turned off, turn off the repeater switch to stop the recorder.
• Turn the power switch to OFF.
• Raise the pen with the pen- raise knob.

3) HOW TO REMOVE RECORDING PAPER?

• When removing the recording paper, turn all switches to OFF, raise the pen. Slowly turn the chart adjusting gear toward the operator until the remaining recording paper is fed. Then, remove the recording paper.
• To remove a partially recorded recording paper, cut the paper. Turn the chart adjusting gear to feed out the paper and then take it out.

4) HOW TO ATTACH RECORDING PAPER?

• Open the paper holders to both sides. Open the base plate toward the operator and place the recording paper in the chart receiving box.
• Let the paper pass between the rollers located on this side of the upper feed drum and let the paper pass over the upper feed drum from the rear to the front.
• Fit the holes of the two edges of the paper uniformly on the pins of the feed drum and be sure to attach the four lines which indicate quadrants so that they come on the left side. At this time, the pen should be up.
• After sufficiently pulling out the paper so that the feed drum turns smoothly, close the base plate. Insert the paper in the lower feed drum from the operator’s side toward the inner side. When the pins of the feed drum are in the holes of the recording paper, feed out the paper by slowly turning the chart adjusting gear toward the operator. When the recording paper on the base plate shows no slack, press the paper with the paper holders at the two sides. This completes the attaching of the recording paper.

5) HOW TO READ RECORDS?

• The recording paper is divided into two parts. The four vertical lines of the left side are for the zone pen which indicated the quadrants of the ship’s course. The other part of the recording paper is for the course pen which indicated the ship’s course.
• The horizontal lines on the recording paper indicate time and are drawn every ten minutes. The time is indicated on the right side of the recording paper.  
• The line scribed by the zone pen indicates the quadrants of the ship’s course. The line scribed by the course pen indicates the ship’s course. When the numeral indicating the bearing with respect to the quadrant belonging to the ship is read from the position of the course pen along the vertical line on the recording paper, the numeral indicates the course of the ship.
• To use the remaining chart after removing the partially recorded paper, cut off the angle of the cut section of the chart about 5cm when putting it into the lower feed wheel.
• Be sure to read the azimuth scale from left to right in the cases of the first and third quadrants and   in the case of the second and fourth quadrants, read the azimuth scale from right to left.

6) HOW TO USE VERNIER SCALE?

• A vernier scale is provided at the right side of the paper chart to facilitate reading the chart to 1 minute intervals of time. To use the vernier, observe which line on the vernier scale is aligned with a horizontal line on the chart. Use this figure as a minute digit and add the indicated numner of minutes to the time stamped on the chart, at the right of the section the COURSE PEN is on. Suppose the COURSE PEN is at a position between the horizontal lines designated 20 and 30 at the right, and that the hour beneath these designation is 5pm. Now suppose line #6 on the vernier scale is aligned with a chart line. The indicated time at the pen position then is 5:26 PM.
• The vernier scale may be used to start the record at any particular time. Hence, if the desired time of start is 5:26 PM, that particular section of the paper which bears the designated time is brought under the pens, and the feed roller clutch is engaged as previously described.

3. MAINTENANCE OF COURSE RECORDER

1) general  .

           Except for checks, course recorder does not require any maintenance.

2) CHECKS  

           It is necessary to check the recording conditions daily.

• Make sure that the ship’s course, course pen and zone pen are turned completely.
• Make sure that the time on the recording paper and the ship’s time match.
• Make sure that the recording paper is being fed in the proper condition.

3) ADJUSTMENT

• Since each of the zone and course pens is attached by a pen mounting screw, if the time of each does not match, loosen the mounting screw and then each can be matched to the 0 position of the vernier scale.
• Each of the zone, course and rudder angle pen is fixed by its holder; loosen the two screws of this holder for parallel movements.
• When the line scribed by any pen is not clear, the pen point has become round or the spring is weakened. In the former case, replace the pen. In the later case, insert the plain washer with a thickness of 0.5mm – 1.0mm in the screw located below the two locking screws of the pen holder to increase the force of the spring.

  CAUTION : A suitable force of the spring is 60gr +/- 12gr as measured at the bending section of the pen. No optimum recording is possible when the force of the spring is greater or smaller than the value given above.

US1975180A - Course recorder - Google Patents

• USPTO PatentCenter
• USPTO Assignment
• Global Dossier

Classifications

• G — PHYSICS
• G01 — MEASURING; TESTING
• G01C — MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
• G01C17/00 — Compasses; Devices for ascertaining true or magnetic north for navigation or surveying purposes

Description

Priority applications (1), applications claiming priority (1), publications (1), id=23271679, family applications (1), country status (1), cited by (3).

• 1928-12-15 US US326307A patent/US1975180A/en not_active Expired - Lifetime

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Gyro Compass on Ships: Construction, Working, and Usage

A Gyro compass is a form of gyroscope, used widely on ships employing an electrically powered, fast-spinning gyroscope wheel and frictional forces among other factors utilising the basic physical laws, influences of gravity and the Earth’s rotation to find the true north.

Construction

Gyro compass has become one indispensable instrument in almost all merchant ships or naval vessels for its ability to detect the direction of the true north and not the magnetic north. It is comprised of the following units:

• Master Compass : Discovers and maintains the true north reading with the help of a gyroscope.
• Repeater Compasses : Receive and indicate the true direction transmitted electrically from the Master Compass.
• Course Recorder : Makes a continuous record of the manoeuvring on a moving strip of paper.
• Control Panel : Governs the electrical operation of the system and ascertains the running condition by means of a suitable meter.
• Voltage Regulator : Maintains constant supply of the ship to the motor-generator.
• Alarm Unit : Indicates failure of the ship’s supply.
• Amplifier Panel : Controls the follow-up system.
• Motor Generator : Converts the ship’s DC supply to AC and energizes the Compass equipment.

Gyro compasses are linked to the repeater compasses via one transmission system. The fast-spinning rotor attached weighs from 1.25 pounds to 55 pounds.

It is driven thousands of revolutions per minute by another electric motor. However, the most essential part of a Gyro compass system is the spinning wheel, which is known as the Gyroscope.

External magnetic fields which deflect normal compasses cannot affect Gyro compasses. When a ship alters its course the independently driven framework called ‘Phantom’ moves with it, but the rotor system continues to point northward.

This lack of alignment enables it to send a signal to the driving motor, which moves the phantom step in with the rotor system again in a path where the phantom may have crossed only a fraction of a degree or several degrees of the compass circle.

As soon as they are aligned, electrical impulses are sent by the phantom to the repeater compasses for each degree it traverses.

The Gyroscope in the Gyrocompass is mounted in such a way so that it can move freely about three mutually perpendicular axes and is controlled as to enable its axis of spin settled parallel with the true meridian, influenced by the Earth’s rotation and gravity.

The Gyrocompass system applications are based upon two fundamental characteristics, which are:

• Gyroscopic Inertia : The tendency of any revolving body to uphold its plane of rotation.
• Precession : A property that causes the gyroscope to move, when a couple is applied. But instead of moving in the direction of the couple, it moves at right angles to the axis of the applied couple and also the spinning wheel.

These two properties and the utilization of the Earth’s two natural forces, rotation and gravity, enacts the Gyrocompass to seek true north.

Once settled on the true meridian the rotor indefinitely will remain there as long as the electrical supply of the ship remains constant and unaltered and unaffected by external forces.

Usage and Errors

Gyro compasses are pre-eminently used in most ships in order to detect true north, steer, and find positions and record courses.

But due to the ship’s course, speed and latitude, there could appear some steaming errors. It has been found that on Northerly courses the Gyro compass north is slightly deflected to the West of the true meridian whereas on Southerly courses it is deflected to the East.

Modern ships use a GPS system or other navigational aids to feed data to the Gyrocompass for correcting the error. An orthogonal triad of fibre optic design and also ring laser gyroscopes which apply the principles of optical path difference to determine the rate of rotation, instead of depending upon mechanical parts, may help eliminate the flaws and detect true north.

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An Introduction to Fluxgate Compass 

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14 Comments

pleasehelp.compass with cover,like divers helmit, has veiwing glass init, electric light and oil lamp.cover comes off with half turn. beleav off american frigate

It is helpful as it is in plain language. I appreciate it.

can you please state the main systems under the control of the gyrocampass and explain it?

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As a ship moves from one side of the earth to the other, wouldn’t the gyroscope flip upside down? If it is indeed spinning to maintain angular momentum, the coronal, axial, and sagittal planes would remain the same. Even if the gyroscope were to remain in a fixed location (ship anchored at a port), the earth is rotating. If the earth rotates once, the gyroscope in the anchored ship should do a complete 360° flip.

Does anyone here have an explanation?

My ship staying at port/docking for a long time, do i have to take a gyro compass error in everyday?

Please advise!

Thanks Brgds, Nawir

How often must the course recorder be aligned with the gyro course? Why is this important and how is the alignment being recorded?

I have a compass that is heavy, round and has liquid in it. Can you tell me what it is called?

HOW IS THE TRANSMISSION EFFECTED FROM THE MASTER COMPASS TO THE REPEATERS?

@Corrine I believe that it is a magnetic compass

I would think the 360 applys,like a clock laying flat on the floor,not standing up right like on the wall.?

Is it possible to create a portable Gyrocompass as the one in ships is big and heavy?

El sistema giroscopico, inventado por Karl Anschutsx en 1912, sufrio variantrs tecnológicas a traves de los años, sumando mas giroscopos en su nucleo, y mejorando los sensores de campo. Las infimas desviaciones latitudinales (+/-0.05° en latitudes >70°) fueron compensadas mediante sistemas de control electronico, pero, toda esa tecnología murió a principios del siglo XXI, al crearse el giroscopio laser, que no utiliza partes moviles ni giroscopos. Es libre de mantenimiento y de desvios.

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