Improvements in Apparatus for Measuring Angles, Specially Adapted for Ascertaining a Vessel's True Position at Sea.
Year: 1887

page_text: Date of Application, 17th Sept., 1887
Complete Specification Left, 18th June, 1888
Complete Specification Accepted, 17th Aug., 1888
Improvements in Apparatus for Measuring Angles, Specially Adapted
for Ascertaining a Vessel's True Position at Sea.
1, THEODORE LEPORTIER of Water Street, Liverpool in the County of Lancaster,
Master Mariner, do hereby declare the nature of this invention to be as follows:-
The invention relates to a simple and portable apparatus for measuring angles,
specially adapted for laying down on a chart a vessel's true position at sea.
In carrying out the invention I provide a frame preferably made circular, the
circumference of which may be divided into four parts, representing the four points
of the compass. Each of these four divisions may be sub-divided into 90 parts
representing degrees.
The disc is supported and pivoted in any convenient manner to a bed plate or frame
so that it can be rotated therein. The pivot is removable so that the scale may be
easily taken off the bed, when desired. Its end is preferably provided with a point
for the purpose hereafter described. The bed plate can be itself supported on brackets
provided, if desired, with a clamping screw, so that it can readily be secured in a
convenient position. The bed plate is preferably pivoted to the frame, and provided
with a weight so that its surface, when used on board a ship, will remain avel
notwithstanding the motion.
The circular scale has attached to it a leg or arm preferably in a straight line
drawn from the axis of the instrument, and intersecting one of the four divisions of
the scale, such for example that marked North. The remaining divisions may be
marked with the other points of the compass namely S.E. and W. Upon the same
axis as the scale I pivot two other arms or legs capable of revolving on the scale and
being fixed, when required, by clamping screws in any position thereon. Each arm
is provided with vanes or sight holes so that they may be adjusted to the object on
which an observation is made. The scale can be fixed in any desired position by
means of a clamping screw attached to the bed plate. The arms are capable of
revolving on their axis when the scale is clamped.

page_text: When it is desired to ascertain the position of a vessel when three objects are in
sight, the action is as follows:
seen.
The instrument is placed upon any part of the vessel from which the objects can be
First the leg or arm which is fixed to the scale (in my model machine it is
the middle one) is directed to one of the objects, and adjusted thereto by means of
the sight holes or vanes. The scale is then clamped to the bed. The other legs or
arms are directed to the other objects and adjusted in a similar way, until the sight
holes are in the line of sight. The arms are then clamped to the scales. The scale
can now be unclamped from the bed, and placed upon the chart. When the three
legs cover the representation on the chart of the three objects, which have been
observed, the axis of the instrument indicates the vessel's position. This can be
marked on the chart by means of the pointed pivot before mentioned, or in other
convenient manner. When only two objects are in sight the instrument is placed on
the fore and aft line of the vessel, as would be required in an ordinary Pelorus. One
of the legs of the instrument is placed on that line and clamped. The other two legs
are now directed to the two objects and adjusted by means of the sight holes as before
described. They are then clamped, and the instrument placed on the chart. The
ship's line of course is marked on the chart, and the leg of the instrument, which
was directed fore and aft, is moved parallel with that line until the other legs cover
their respective objects. The ships true position can thus be marked by the centre
of the instrument as before. A small pair of parallel rollers may be attached to the
instrument to facilitate this operation. In place of a circular scale, a plain disc, not
provided with a scale, may of course be supplied.
When a vessel is in narrow waters, where two objects are sometimes to be found in
a line, the position can readily be ascertained by taking the bearing with one leg,
and with another leg that of a third object. The apparatus may also be used as an
Azimuth Compass. For this purpose I provide a shadow-pin which can readily be
attached to one or any of the legs or arms. The apparatus being fixed on the fore
and aft line as before and set to the ships' head, the shadow pin is attached on one of
the arms which is turned towards the sun and the bearings taken in the usual way.
If the angles are very large one of the legs can be unshipped and placed on the
instrument where wanted.
It is evident that the apparatus may also be used for measuring angles of distant
objects, and for other purposes bosides for use at sea.
Dated this 16th day of September 1887

page_text: Improvements in Apparatus for Measuring Angles, Specially Adapted
for Ascertaining a Vessel's True Position at Sea.
I THEODORE LEPORTIER of Water Street, Liverpool, in the County of Lancaster,
Master Mariner, 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 :-
The invention relates to a simple and portable apparatus for measuring angles,
specially adapted for ascertaining and laying down on a chart, a vessel's true position
at sea.
I carry out my invention as follows, reference being had to the accompanying
drawings, which set forth a convenient form of the apparatus, and illustrate the method
of using it.
Figure 1 is an elevation of the entire apparatus.
Figure 2 is a plan of the upper portion of same.
Figure 3 is an elevation (on a reduced scale) of the supporting frame and bed
plaie, with the upper parts of the apparatus removed.
Figure 4 is a plan (also on a reduced scale) illustrating the method of laying out a
vossel's position on a chart.
In carrying out the invention, I provide a scale or disc A preferably made circular,
the circumference of which may be divided into four parts as in Figure 2, representing
the four points of the compass. Each of these four divisions may be subdivided into
90 parts, representing degrees.
The scale A is supported upon, and pivoted in any convenient manner to a bed
plate or frame B, so that it can be rotated thereon. The pivot may be removable, so
that the scale may be easily taken off the bed plate when desired, and its end may be
provided with a point for a purpose hereafter described. Or instead of being remov-
able, the pivot may be attached to the bed plate B as shown in Figure 1, and the
scale may be formed with a central hole, through which the pivot may pass, and with
an elongated boss a carrying a binding screw a' by which the scale may be held
stationary on its pivot.
The bed plate may itself be supported on brackets provided, if desired, with a
clamping screw, so that it can readily be secured in a convenient position. The bed
plate is, however, preferably pivoted in gimbals (to a frame D, and provided with a
weight so that its surface, when used on board a ship, will remain level not-
withstanding the motion. The frame D may be conveniently slid into or otherwise
secured to a plate D, which may be attached to the rail of the bridge, or in other
suitable position.
The circular scale A has attached to it a leg or arm E, having one edge preferably
in a straight line drawn from the axis of the instrument, and intersecting one of the
four divisions of the scale, such for example as that marked North. The remaining

page_text: divisions may be marked with the other points of the compass, namely S.E. and W.
Upon the same axis as the scale, preferably upon the boss a, I pivot two other arms or
legs F, G, also having their working edges in a vertical plane passing through the
axis of the instrument. These arms are capable of revolving on the scale, but are
also capable of being fixed thereon in any position, by clamping screws f, g.
Each leg acts as a station pointer, and is provided with a vertical vane or sighting
stem H on one side of the axis of the instrument, and on the other side of the axis,
with a vertical sight hole or slot H¹ formed in an upright stem, preferably on the
rear end of the leg. On each leg, the slot H', and one edge of the stem H, lic in
the same vertical plane as the axis of the instrument, and the working edge of the leg.
Or instead of a vane and sight hole, each leg may be provided with two vanes or two
sight holes. On the drawings, the upright stem carrying the sight hole H¹ of the
leg E is shown attached to the disc A instead of to the leg itself, but this is a mere
detail of construction.
When it is desired to ascertain the position of a vessel when three known objects
are in sight, the action is as follows:
The instrument is placed upon any part of the vessel from which the objects can be
seen. First the leg or arm E, (preferably the middle one) which is fixed to the
scale, is directed to one of the objects (preferably to the centre one of the three), and
adjusted thereto by means of the sight hole H₁ and vane H. The scale A is then
clamped to the bed B. The other two legs or arms F, G, are directed to the other
two objects, and adjusted in a similar way until their sight holes and vanes are in the
line of sight. The arms are then clamped to the scale by the screws f and g. The
scale can now be unclamped from the bed by slacking the screw a¹, and placed
upon the chart J, Figure 4. When the working edges of the three legs pass
through the representation on the chart of the three objects which have been
observed, the axis of the instrument, which is the central point of the hole in scale,
indicates the vessel's position. This can be marked on the chart by means of a pencil
or pointed pivot, or in other convenient manner. Or when the scale is provided
with a pointed pivot as before mentioned instead of with a central hole, the point of
the said pivot may be utilised for marking the chart,
When only two objects are in sight, the instrument is placed on the fore and aft
line of the vessel as would be required in an ordinary Pelorus. One of the legs
of the instrument is adjusted to this line, and clamped. The other two legs are
now directed to the two objects, and adjusted by means of the sight holes and
vanes as before described. They are then clamped, and the instrument placed on
the chart upon which the ship's line of course has been marked. The leg of the
instrument, which was directed fore and aft, is now moved parallel with the course
line until the working edges of the other legs cover the representations on the
chart of their respective objects. The ship's true.position can thus be marked by
the centre of the instrument as before. A small parallel ruler K may be attached
to the instrument to facilitate this operation, the links of the ruler being pre-
ferably slipped over small pins on the legs. In place of a circular scale, a
plain disc, not provided with a scale, may of course be supplied.
When a vessel is in narrow waters, where two known objects are sometimes to
be found in a line, the position can readily be ascertained by taking the bearing
with one leg, and with another leg that of a third known object.
The apparatus may also be used as a course corrector. For this purpose, a vertical
shadow pin L is inserted into a small hole in or otherwise secured above the centre
of the axial pivot b. The apparatus being fixed on the fore and aft line as before,
and set to the ship's head, the bearings are taken in the usual way.
A style M similar to the shadow pin L is also provided. The style is attached
to two straps m, which are slipped over one of the vanes H, and it may be used
in conjunction with the shadow pin L to take the bearings of high objects at a
comparatively short distance away, such as light-houses, land-marks, etcetera.
If the angles are very large, one of the legs can be unshipped and placed on the
instrument where wanted.

page_text: It is evident that the apparatus may also be used for measuring angles of distant
objects, and for other purposes besides for use at sea.
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:
1. An apparatus for ascertaining a vessel's position at sea by means of two or more
known objects or bearings, consisting of a horizontal disc A or its equivalent adjustably
and detachably mounted on a central pivot b upon a suitable bed plate, a horizontal
radial arm E attached to said disc, and provided on opposite sides of the same diameter
with a vertical vane and sight hole respectively, or equivalent apparatus, and two
diametric arms F, G, provided with sights and capable of angular adjustment about
the axis of said pivot with reference to the said arm, and to each other, substantially
as and for the purposes described.
2. In combination with one of the arms E, F, G, a parallel ruler K detachably
connected thereto, for the purpose of facilitating the adjustment of the instrument
upon the chart, substantially as set forth.
3. As an instrument for measuring angles, the combination of the graduated disc A,
and the station pointers E, F, G, provided with sighting vanes or holes, substantially
as described.
4. The combination of the graduated horizontal disc A, one of the radial arms
carried thereby, and adjusted to the fore and aft line of the vessel, and the vertical
shadow pin L placed in the axis of the said disc and either with or without the vertical
style M, substantially as and for the purposes set forth.
5. An apparatus for ascertaining a vessel's position at sea, having station pointers
with sight vanes, and a gimbal table or disc held in horizontal position by a weight or
otherwise, substantially as described.