Improvements in Apparatus for Measuring Angles, specially applic- able for Determining a Vessel's Correct Distance from a Fixed Point on Land.
Year: 1899

page_text: Improvements in Apparatus for Measuring Angles, specially applic-
able for Determining a Vessel's Correct Distance from a Fixed
Point on Land.
I, JOHN EDWARD HACKETT, of 88, Rockfield Road, Anfield, Liverpool, in the
County of Lancaster, Engineer, do hereby declare the nature of this invention
to be as follows:-
This invention relates to apparatus for measuring angles, specially applicable
for determining a vessel's correct distance from a fixed point or points on land,
and is designed to enable the officer on duty to ascertain this distance without
leaving the deck or having to refer to the chart. Hitherto this data has been
obtained by noting the exact time by a watch or clock when the light house or
other fixed object bears by compass four points (45°) from the course, and again
noting the time when it bears on the beam 90° from the course, the distance
run by the ship in the interval being the distance of the object when abeam.
This system is defective in so far that the ship has to travel without changing
her course a considerable distance between the time when the object bore 45°
from the course and the time when it bore 90° from the course.
In many
instances, therefore, it has been impossible to determine the distance of the
object by this system owing to the ship being unable to travel the requisite
distance without changing her course.
At one
This objection I overcome by my present invention. It comprises a central
leg graduated with divisions representing miles or other suitable units.
end of this leg is pivoted an arm radiating from the pivot which can be worked
independently of the leg and clamped in any required position. Another pivoted
arm is mounted on the leg, and made capable of sliding longitudinally thereon,
so as to approach nearer to the other arm or recede therefrom, and capable also
of being clamped in any position. Both these arms are graduated and may be
provided at their pivots with a scale of degrees. The movable arms turn round
their respective centres or axes, and there being a scale of degrees round the
pivots where the arms pass outwards, the angle either of them make with the
fixed leg, which constitutes the zero point of the circle, can be readily measured.
In action when a fixed point on shore becomes visible, the central leg is set
by compass or otherwise to the ship's course, and one of the pivoted arms is
set in line with the fixed object and clamped in position at an angle of so many
degrees from the course. The ship is allowed to run a certain known distance,
and the pivot of the other arm moved along the leg a distance to correspond, a
fresh observation of the fixed object in question is taken placing the arm in line
with the object. The ship having travelled a certain distance in the interval,
the two arms will be at different angles from the course and they will bisect
each other at a certain point in their length. The distance in units on the leg
between the pivoted arins, will represent the distance run, and the distance

page_text: from the pivot of one arm to the point of intersection with the other arm will
indicate the actual distance of the vessel from the fixed object on shore, while a
perpendicular to the point of intersection from the leg will be distance of the
vessel when abeam. For example, let the ship be steering north by compass at
a known speed per hour. At 9 a.m. a lighthouse is observed to bear 30° from
the course. Set the pivoted arm in line with the object, namely 30° from
the course and clamp it in position. At a certain time later when the ship has
travelled a known distance say 3 miles the object is found to bear 45° from the
course. The other pivoted arm is accordingly moved longitudinally along the
fixed leg three units and then set in line with the object and clamped in position
at 45°. The distance from the pivot of said arm to the point of its intersection
with the other arm is the distance of the ship from the point in question, while
the distance between the two pivots represents the distance the ship travelled
in the interval. An imaginary perpendicular line drawn to the point of inter-
section from the fixed leg will represent the distance of the vessel off the light-
house when abeam. If it is desired to determine the correct distance of the
vessel from two fixed points, a pair of arms are provided on each pivot, and in
this way the distance of fixed objects forward of the beam and abaft the beam
can be determined; the same also with three fixed objects, in which case three
arms are provided on each pivot and so on. A system of this kind will be
especially useful at night when it happens that no other method is available
for determining the distance of a vessel from the shore.
Dated this 24th day of August 1900
Improvements in Apparatus for Measuring Angles, specially applic-
able for Determining a Vessel's Correct Distance from a Fixed
Point on Land.
I, JOHN EDWARD HACKETT, of 88, Rockfield Road, Anfield, Liverpool, in the
County of Lancaster, Engineer, do hereby declare the nature of this invention
and in what manner the same is to be performed, to be particularly described
and ascertained in and by the following statement:-
This invention relates to apparatus for measuring angles, specially applicable
for determining a vessel's correct distance from a fixed point or points on land,
and is designed to enable the officer on duty to ascertain this distance without
leaving the deck or having to refer to the chart. Hitherto this data has been
obtained by noting the exact time by a watch or clock when the light house or
other fixed object bears by compass four points (45°) from the course, and again
noting the time when it bears on the beam 90° from the course, the distance
run by the ship in the interval being the distance of the object when abeam.
This system is defective in so far that the ship has to travel without changing
her course a considerable distance between the time when the object bore 45°
from the course and the time when it bore 90° from the course.
In many
instances, therefore, it has been impossible to determine the distance of the
object by this system owing to the ship being unable to travel the requisite
distance without changing her course.
This objection I overcome by my present invention which will be understood

page_text: ying description, reference being mun to the accompanying araw-
ings, in which,
Figure 1 is a plan of my apparatus ;
Figure 2, an edge view of a portion of same.
The invention comprises a central leg A graduated with divisions representing
miles or other suitable units. At one end of this leg A is pivoted an arm B
radiating from the pivot C which can be worked independently of the leg A and
clamped in any required position by a clamping nut D. Another pivoted arm E
is mounted on the le A, and made capable of sliding longitudinally thereon,
F being guides to enable this sliding to take place so as to approach nearer to
the other arm B or recede therefrom. The arm is capable of being clamped in
any position by the nut G. Both these arms are graduated and may be provided
at their pivots with a scale of degrees H. The movable arms B and E turn round
their respective centres or axes, and there being a scale of degrees H round the
pivots where the arms pass outwards, the angle either of them make with the
fixed leg A which constitutes the zero point of the circle, can be readily
measured.
In action when a fixed point on shore becomes visible, the central leg A is set
by compass or otherwise to the ship's course, and one of the pivoted arms, say B,
is set in line with the fixed object and clamped in position at an angle of so
many degrees from the course. The ship is allowed to run a certain known
distance, and the pivot of the other arm E moved along the leg A a distance to
correspond. A fresh observation of the fixed object in question taken, placing
the arm E in line with the object. The ship having travelled a certain distance
in the interval, the two arms B and E will be at different angles from the
course, such for example as that shown by the full lines of arm B and dotted
lines of arm E, and they will bisect each other at a certain point in their length.
The distance in units on the leg A between the pivots of the pivoted arms B
and E, will represent the distance run by the vessel, and the distance from the
pivot of arm 1 to the point of intersection with the other arm E, will indicate
the actual distance of the vessel from the fixed object on shore, while a perpen-
dicular to the point of intersection from the leg A will be the distance of the
vessel when abeam. For example, let the ship be steering north by compass an
a known speed per hour, at nine a.m. a lighthouse is observed to bear 30° from
the course. Set the pivoted arm B in line with the object, namely 30° from
the course and clamp it in position by the nut D. At a certain time later when
the ship has travelled a known distance, say three miles, the object is found to
bear 45° from the course. The other pivoted arm E is accordingly moved longi-
tudinally along the fixed leg A three units, and is set in line with the object,
and clamped in position at 45°. The distance on the scale from the pivot of
said arm B to the point of its intersection with the other arm E, is the distance of
the ship from the point in question, while the distance between the two pivots
represents the distance the ship has travelled in the interval. An imaginary
perpendicular line drawn to the point of intersection of B and E from the fixed
leg A will represent the distance of the vessel off the lighthouse when abeam.
If it is desired to determine the correct distance of the vessel from two fixed
points, additional arms B' and E' are fitted, so as to provide a pair of arms on
each pivot, and in this way the distance of fixed objects forward of the beam and
abaft the beam can be determined. The same also with three fixed objects, in
which case three arms are provided on each pivot and so on. The leg A is by
preference bent as shown in Figure 2 to enable it to be fastened on to any
suitable fixed object.
The scale of degrees H is made in semicircular form, thus enabling the
instrument to shut up in a comparatively small space, as the semi-circular discs
will close neatly together. An invention of this kind will be specially useful
at night when it happens that no other method is available for determining the
distance of a vessel from the shore.

page_text: Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:-
a
1. In apparatus for measuring angles, especially applicable for determining
vessel's correct distance at sea from a fixed point or points on land, consisting
of a central leg graduated with divisions representing miles or other suitable
units, and a pair of pivoted radial arms or legs capable of angular adjustment
about the axes of their pivots with reference to said central leg and to each other,
one of said arms being pivoted at one end of said leg and the other arm so
mounted on the leg that it can be slid longitudinally thereon and adjusted to
approach nearer to or recede from the other pivot, substantially as described.
2. The combination of the graduated leg A adjusted to the fore and aft line of
the vessel, the graduated scale of degrees H carried thereby at one end thereof,
and another scale of degrees H so mounted on the leg, as to be capable of longi-
tudinal adjustment, a graduated arm or sets of arms B B¹, pivoted to one scale,
and another graduated arm or sets of arms E E, pivoted to the other scale, said
arms being capable of angular adjustment about the axis of their pirots, with
reference to the central leg A and to each other, substantially as and for the
purposes described.
3. In apparatus for measuring angles, (especially applicable for determining
a vessel's correct distance at sea from a fixed point or points on land), having a
central leg graduated with divisions and pivoted radial arms or legs capable of
angular adjustment, the provision of two or more arms on each pivot in such a
manner that the distance of two or more fixed objects can be determined, sub-
stantially as described.
4. The general combined arrangement and construction of parts forming my
improved apparatus for determining a vessel's correct distance at sea from a fixed
point or points on land, substantially as set forth.
Dated this 24th day of May 1900.
WM. P. THOMPSON & Co.,
Patent Agents, of Liverpool, Manchester, Birmingham & London.