IMPROVEMENTS IN APPARATUS FOR ASCERTAINING THE DISTANCE OF AN OBJECT FROM AN OBSERVER; ESPECIALLY APPLICABLE FOR USE ON BOARD SHIP
Year: 1883

page_text: PROVISIONAL SPECIFICATION left by Cornelius Edward Kelway at the
Office of the Commissioners of Patents on the 18th July 1883.
CORNELIUS EDWARD KELWAY, of Lombard Street, in the City of London
"IMPROVEMENTS IN APPARATUS FOR ASCERTAINING THE DISTANCE OF AN OBJECT
FROM AN OBSERVER; ESPECIALLY APPLICABLE FOR USE ON BOARD SHIP
"
This invention relates to apparatus used for the purpose of ascertaining the
distance of any remote object, in which the angles made at different points upon a
base line of known length are taken and the distance of the object thus ascertained.
It has for its object improvements in such apparatus by which it is made very
simple, light, cheap, and easily used.
The improved apparatus is especially useful for the purpose of ascertaining the
distance of a remote object on board ship, as for instance for the purpose of finding
the range for guns.
Assuming that it is to be used for such purpose I take a flat rule or plate having
a longitudinal slot divided into spaces representing miles, knots, or other determined
distances or fractions of such distances.
At one end of the plate is fixed a centre upon which turns a straight edge or
rule one edge of which passes through the centre upon which it turns, and a
graduated sector or scale by which the angle which such edge makes with the slot
in the plate can be measured and indicated.
A second rule or straight edge having a graduated edge, also turns upon a
centre similar to that first described, but capable of being moved into any position
in the slot and adjusted there, and a second graduated sector or scale indicates the
angle which the second straight edge makes with the slot.
The angle which the ships course makes with the fixed or other object whose
distance is to be determined, being taken in the ordinary way at any point in her
course, the straight edge turning upon the fixed centre is adjusted and fixed so as
to make a similar angle with the slot in the plate. The vessel is then run on the
same course for a certain determined distance and the angle which the direction of
her course then makes with the distant fixed object is again measured, and is laid
down upon the instrument by means of the second straight edge the moveable

page_text: centre of which has been first moved along the slot for a distance corresponding
upon the scale with that which the ship has run since the first observation."
The distance run, therefore, being measured by the space between the centres of
the two straight edges, the direction of the distant object at the beginning and end
of such distance is represented by the graduated edges of the two straight edges,
and the point of their intersection represents the position of the distant object, the
distance of which is shewn upon the graduated edge of the second straight edge
where it intersects the first, the graduations corresponding with those upon the
slotted rule by which the distance run by the vessel is measured.
Allowance can be readily made for cross currents or other causes affecting the
straight course of the vessel, the angle between the slotted plate and the first
graduated straight edge being increased or lessened according to the requisite
allowance estimated by tables prepared for the purpose or in other ways.
And where it is necessary that the course of the vessel should be altered during
its measured run as described, a third arm may be arranged so as to turn upon the
moveable centre described, this third arm being itself slotted and graduated and
carrying in its slot the moveable centre upon which the second moveable arm
turns. In this form of the apparatus, the centre of the third arm is moved along
the slot to a distance corresponding with the first part of the vessels course, and it
is then turned and fixed at an angle corresponding with that of the direction of
the second part of the vessel's run with the first. The moveable centre. of the
second graduated straight edge is then adjusted and fixed in this third arm at a
point corresponding with that at which the second observation is taken, and the
graduated straight edge is itself fixed in a position corresponding with the angle
formed by the distant object at such observation. The distance to the point of
intersection of the two straight edges, representing the position of the distant
object, can then be read off as before.
The sectors, or graduated indicating scales, may be fixed in any convenient
position and method so that the angles of the several straight edges can be readily
adjusted and measured.
Instead of the method of using the apparatus described, it may be modified by
taking simultaneously the angles made by the direction of the ship's course with
two distant objects, the distance between which is known.
Apparatus constructed according to my invention may be used to ascertain the
distance of objects for range finding or other purposes in other circumstances as
well as on board ships.