The Ideal Compass

F you were to conceive of a compass which would be free from all the troubles and errors found in most compasses, which would relieve you of all the worry and care the present compass requires, a compass which would be accurate and reliable, a compass which would be the Ideal Compass under all conditions, you would undoubtedly conceive of a compass that had the following characteristics:

1.It must point True North.

2.It must free you from the necessity of making calculations and corrections.

3.It must free you from compensating the compass for errors.

4.It must free you from the burden of swinging the ship, or otherwise taking the deviation of your compass.

5.It must not be influenced by inherent magnetism of the ship.

6.It must not be influenced by any change in the character or disposition of the cargo.

7.It must not be influenced directly or indirectly by any temperature changes.

8.It must not be influenced by the roll or pitch of the ship.

9.It must not be influenced by any weather conditions.

10.In the event of failure, or error, it should give instant warning.

Comparison of the Magnetic Compass with the Sperry Gyro-Compass

Let us compare the Magnetic Compass with the Sperry Gyro-Compass and determine which more nearly approaches the Ideal Compass.

True North

The Magnetic Compass

The Mag­ne­tic Com­pass does not point to True North, it points to Mag­ne­tic North, which is about 800 miles from the True North Pole.

The Sper­ry Gyro-Com­pass

The Sperry Gyro-Com­pass, which is not a Mag­ne­tic Com­pass, and is not af­fect­ed by a mag­ne­tism of any sort, and de­rives its di­rec­tive force from the earth’s ro­ta­tion, points True North. It does not point to the Mag­ne­tic North Pole.

A Galleon, the treasure ship of the Spanish Main.

Freedom From Calculation

Every time a ship’s course is laid or changed, or its po­si­tion noted, the nav­i­ga­tor must make and apply cal­cu­la­tions to cor­rect the er­rors caused by var­i­a­tion of the earth’s mag­netic fields, and dev­i­a­tion due to local con­di­tions about the ship. Mis­takes are fre­quent­ly made in ap­ply­ing the cor­rec­tion fac­tors by ap­ply­ing them to the wrong side. An er­ror is thus in­tro­duced, which in mag­ni­tude is twice the cor­rec­tion factor. Ins­tances are re­port­ed of ships being 200 miles out of their courses as a result.

The Gyro-Compass re­quires no cor­rec­tions since it is un­dis­turbed by var­i­a­tions or any local mag­ne­tic con­di­tions. The read­ing in­di­ca­ted by the Sper­ry Gyro-Com­pass is not ap­prox­i­mate—it is ab­so­lute­ly and im­me­diate­ly cor­rect. It is not ne­ces­sary to cor­rect the course every few hours for var­ia­tion—the nav­i­ga­tor is freed from the ne­ces­si­ty of ma­king cal­cu­la­tions.

Freedom From Compensation

After the nav­i­ga­tor has made cal­cu­la­tions for the dev­i­a­tion er­rors of the Mag­ne­tic Com­pass, they must be ap­plied by means of man­i­pu­la­ting the soft iron globes and com­pen­sa­ting mag­nets. This is an op­er­a­tion re­quir­ing such a high de­gree of skill that only trained men called Com­pass Ad­just­ers are qual­i­fied for the work.

The oc­cas­ion­al turn­ing of a thumb nut is the only com­pen­sa­tion nec­es­sary in the use of a Sper­ry Gy­ro-Com­pass. No tables or curves are re­quired. The ship’s Nav­i­gat­ing Of­ficer makes this ad­just­ment with ease.

A Ship of the Line, the dreadnought of former days.

Freedom From Checking Deviation

Each time a com­pass is com­pen­sa­ted it is nec­es­sary to check the com­pen­sa­tion by check­ing the dev­i­a­tion on var­ious head­ings. This may be done by the use of de­flec­tor mag­nets. A more exact method is to swing the ship in a circle while bear­ings are taken of a known object on land and the dev­i­a­tion noted on var­ious head­ings. The sun is often taken as a ref­er­ence point for this pur­pose.

It is never nec­es­sary to swing ship or to cor­rect the Gyro-Com­pass for eith­er var­i­a­tion or dev­i­a­tion of any kind. Where a Gyro-Com­pass and a mag­netic com­pass are both used on a ship, the ship may be swung to cor­rect the mag­net­ic com­pass—the Gy­ro-Com­pass fur­nish­ing true head­ings. The time re­quired is thereby ma­ter­i­ally short­ened.

Influences Due to Magnetism of the Ship

When a steel ship is build­ing a sub­per­ma­nent mag­ne­tism is in­duced in its keel, hull, and plates. It causes a com­pass dev­i­a­tion classed as “semi­cir­cu­lar.” This dev­i­a­tion must be com­pen­sat­ed for.

As a ship moves through the earth’s mag­ne­tic fields in its vary­ing quan­ti­ties and dir­ec­tions, a tem­por­ary and varying mag­ne­tism is in­duced in the soft iron of the ship. The re­sul­tant dev­i­a­tion is classed as “quad­ran­tal,” and must be com­pen­sat­ed for.

The Sper­ry is not a Mag­ne­tic Com­pass. Ham­mer­ing, riv­e­ting, and mov­ing through mag­netic fields may in­duce mag­ne­tism in the ship, but will have no ef­fect upon the Sper­ry Gyro-Com­pass.

There is no con­di­tion of the ship or cargo for which the Gyro-Com­pass must be cor­rec­ted.

An American Clipper, highest type of sailing ships.

Influences Due to Cargo

Change in the char­acter or dis­pos­i­tion of the cargo of the ship causes a change in the mag­net­ic fields sur­round­ing the com­pass. These changes must be com­pen­sat­ed for.

The Sper­ry Gy­ro-Com­pass is not af­fect­ed by any cargo. A cargo of iron ore has no more ef­fect upon it than a cargo of cot­ton. You could even carry a load of strong mag­nets with­out caus­ing the slight­est dev­i­a­tion.

Influences Due to Temperature Changes

Changes in the temp­er­a­ture of the stack, due to shift­ing of the wind and force of draft, vary its mag­net­ic char­ac­ter­ist­ics. Cons­e­quent­ly the Mag­netic Com­pass is af­fected.

Temp­er­a­ture changes do not in­flu­ence the Sper­ry Gy­ro-Com­pass.

No mat­ter what the con­di­tions are that change the mag­net­ic char­ac­ter­is­tics of the stack, ship or cargo, they can­not af­fect the Gy­ro-Com­pass, as it has noth­ing what­ev­er to do with mag­ne­tism.

Fulton’s Clermont ushered in the age of steam.

Influences Due to Roll and Pitch of the Ship

The Magnetic Compass

Another error, called heel­ing error, is caused by the change in the dis­pos­i­tion of the material of the ship with ref­er­ence to the com­pass. It is brought about when the ship rolls. For example, a ship heading on a northerly course would, if rolled to port, place all magnetic material of the ship to the east­ward of the compass. This pulls the north end of the com­pass to the east­ward. The action and effect would be just opposite to this on a roll to the star­board. The result is that the needle is caused to oscil­late in either direc­tion. The helms­man in his attempt to keep “on” will cause the ship to traverse a sinuous course.

The card and needle of the mag­netic compass are placed in a bowl filled with a liquid. The purpose in so doing is to make the action of the card some­what slug­gish, so that it will not follow very slight magnetic dis­trac­tions or ship move­ments. Every time the course of the ship is changed the slug­gish action, due to adhesion between the bowl, liquid and card, pulls the com­pass off the mer­i­di­an. Of­ficial test has shown that from three to four minutes are re­quired for the com­pass to over­come this “lag.” The “lag” is some­what less in the dry card compass.

The Sperry Gyro-Compass

Not only is the Sperry Gy­ro-Com­pass unaf­fec­ted by mag­ne­tic con­di­tions, re­sult­ing from the heel­ing error, but before being placed upon the ship it is tested for days under con­di­tions sim­u­lat­ing the mo­tion of the ship in the most severe storm.

A ship steered by the Gyro-Compass trav­erses a straight line course; the Gyro-Com­pass does not os­cil­late with the rol­ling of the ship. It is not nec­es­sary for the helms­man to use as much helm to keep the ship on her course. A great saving is made in the use of the steering engine.

There is no “lag” in the Sper­ry Gy­ro-Com­pass, be­cause it does not leave the mer­i­dian, no mat­ter which way or how quick­ly the ship may turn or zig-zag. Ex­haus­tive tests have been con­duct­ed on com­pas­ses installed on torpedo boat des­troy­ers. Even when zig-zag­ging at top speed in heavy seas the Gy­ro-Com­pass shows no “lag.”

Trav­e­ling the straight line course instead of the sin­u­ous course, ships equipped with the Sper­ry Gy­ro-Com­pass have saved from one to ten per cent in time over the average sched­ule time re­quired to cov­er their courses when steering by the mag­ne­tic com­pass.

The Savannah, first steamship to cross the ocean.

Warning of Unreliability

Due to mag­net­ic storms and any num­ber of other causes the mag­net­ic com­pass may at any time be dis­trac­ted so that it does not in­di­cate cor­rect­ly. Dis­tur­bances are ex­tran­eous and their di­rec­tion and mag­ni­tude can­not be de­ter­mined. The nav­i­gat­or is cons­tant­ly sub­ject to the feel­ing that his comp­ass may not be ac­cu­rate—that he can­not de­pend on it.

About the only thing that will cause an er­ror in the Gy­ro-Com­pass is the fail­ure of the el­ect­ri­cal power sup­ply. Should this con­tin­gen­cy oc­cur an elec­tric bell warns the nav­i­ga­tor. Any dis­tur­bances must orig­i­nate with the mas­ter com­pass and can be quick­ly and ac­cu­rate­ly lo­cated.

The Sperry Gyro-Compass unfailingly points True North under all conditions of weather, ship or cargo. It relieves the navigator of calculation of errors, and tiresome compass compensations. It makes a great saving in time required to “swing ship.” The Sperry Gyro-Compass is, therefore, the Ideal Compass.

The Great Eastern laid the first Atlantic cable.