Improvements in and connected with Instruments for Finding the Distance the Observer is from a Fixed Object at the Time of Observation.
Year: 1891

page_text: Date of Application, 5th Feb., 1891
Complete Specification Left, 5th Nov., 1891-Accepted, 30th Jan., 1842
PROVISIONAL SPECIFICATION.
Improvements in and connected with Instruments for Finding the
Distance the Observer is from a Fixed Object at the Time of
Observation.
I FRANK SAMUEL PETT of 113 Snargate Street Dover Master Mariner do
hereby declare the nature of this invention to be as follows:-
This invention has for object to permit of one or more bearings of a fixed object
to be taken & with the use of the distance run between the bearings or with one
bearing & the known range of the light or the distance the object is visible to find
the distance the observer was or is off the fixed object at the time the first second
or other bearing was observed without the use of a chart.
My improved instrument may consist of a dumb card made of suitable material
in the form of a quarter of a circle or other suitable shape.
The circular edge or side is or may be marked in degrees or points in the same
manner as a compass card from 0° to 90°.
I may divide each straight line which forms the straight sides of the dumb card
into a suitable number of equal parts by means of straight lines (at right angles to
the lines which they divide) numbering them from 0 upwards these numbers
representing miles or other standards of length
I would here observe that these straight lines are extended across the face of
the dumb card as far as found necessary; at present I prefer to extend them to
within half an inch of the circular side of the dumb card.
It will be readily seen that by thus dividing each straight side of the dumb-card
by means of straight lines that the surface or face of the dumb card is marked
into a number of small squares of equal magnitude.
I may attach (by means of a screw or pin to act as a pivot) to the dumb card
at the place where the straight sides of the dumb card meet a pointer or azimuth
vein this pointer is also divided into a number of equal parts from where it is pivoted
to the end & numbered from 0 upwards these numbers representing miles or other
standards of length.
I may also attach by suitable means two pointers or azth. veins each of these
pointers being attached in such a manner to their respective straight sides of
the dumb card that they can be readily moved along the straight sides of the dumb
card. These azth. veins or pointers are also divided & numbered as the first
mentioned azth. vein or pointer.
Or I may dispense with the pointers or pointer & use instead a pair of parallel
rules for placing the bearings on the instrument.
With an instrument so constructed I may take bearings or angles of a distant
fixed object & with the distance run between the bearings find the distance the
fixed object is or was from the observer also the distance the ship will pass say
when the object is abeam & the distance the ship will have to travel before the
object is abeam.
Dated this 4th day of February 1891.

page_text: COMPLETE SPECIFICATION.
Improvements in and connected with Instruments for Finding the
Distance the Observer is from a Fixed Object at the Time of
Observation.
1, FRANK SAMUEL PETT of 113 Snargate Street Dover, 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—
This invention has for its object to permit of one or more bearings of a fixed
object to be taken and with the use of the distance run between the bearings or
with one bearing and the known range of the light or the distance the object is
visible to find the distance the observer was or is off the fixed object at the time
the first, second or other bearing was observed without the use of a chart.
My improved instrument consists of a dumb card made of suitable material
preferably in the form of a semi circle but it may be a quarter of a circle or of
other suitable shape.
The circular edge or side is marked in degrees or points in the same manner as
a compass card from 0° to 90º. Parallel to the straight side of the semi circle on
the face of the dial lines are engraved at equal distances apart and are numbered
from upwards representing miles or other standards of length. I divide these
straight lines into a suitable number of equal parts by means of straight lines (at
right angles to the lines which they divide) numbering them from 0 upwards these
numbers representing miles or other standards of length.
I would here observe that these straight lines are extended across the face of
the dumb card as far as found necessary; I now prefer to extend them to within half
an inch of the circular side of the dumb card.
It will be readily seen that by thus dividing the dumb card by means of straight
lines that the surface or face of the dumb card is marked into a number of small
squares of equal magnitude representing square miles or other standards of measure-
ment. 1 attach (by means of a screw or pin to act as a pivot, or otherwise,) to
the dumb card at the centre of the circle if produced a pointer or azimuth vane.
This pointer which I preferably make of wire but which may also be divided into
a number of equal parts from where it is pivoted to the end and numbered from 0
upwards, these numbers representing miles or other standards of length. I also
attach by any suitable means, one or more pointers or azimuth vanes to the dumb
card so that their respective pivots may be moved along directly over the base
line of the dumb card. These azimuth vanes or pointers are also divided and
numbered as may be the first mentioned azimuth vane or pointer.
The accompanying drawing illustrates my improved instrument particularly
adapted for taking observations at sea.
Figure 1 being a top plan view and
Figure 2 an elevation thereof.
A. indicating the dumb card.
B the centre of the circle.
C the base line set or clamped to the bridge rail so as to be parallel with the keel
of the ship.
D sight vane pivoted at E.
EE sight pins attached to vane D.
F clamp screw.
G graduated sight vane.
H pivot of same.
I sight pins ou G.
On a light being sighted the officer of the watch takes a bearing of it by
means of the sight pins E E¹ attached to the sight vane D, this bearing is clamped
at F and the log noted. After running a suitable distance to change the bearing,

page_text: say six miles from the time of first. observation, the sight vane G is moved along
the base line C until the pivot H comes, directly over line 6 which represents the
six miles run; this sight vane which is also provided with two sight pins I, I¹, is
now used to take a second bearing of the light or object after which will be
found that the fore and aft division on the dial at which the azimuth vanes interset
one another represents the distance the ship will pass the object when abeam, in
this case 9 miles; the athwart ship division at the point of intersection of the
azimuth vanes, 15, represents the number of miles the ship will have to travel
on her course before the object is abeam from the first bearing again, the number
of miles on the graduated sight vane G at the point of intersection, in this case 13,
is the distance the ship is from the object on that line of bearing. (If the operation
be repeated with consonant beam results it is evident that the ship is making her
course. If the results are discordant that indicates to what extent the ship is
being set in or out from her course); this distance is now utilized to shape a
fresh course if desired, even if the deviation of the compass is not known, as
follows:-
To pass off a fixed object at any desired distance, set the pivot of the graduated
vane G at B on the base line, look on the vane for the number corresponding to
the range of the light (or distance from the object). Move the vane G in azimuth
until this number cuts the fore and aft line on the face of the dial A which
corresponds to the desired distance at which the navigator wants to pass the object
when abeam. When this is done alter the ship's course until the sight pins I I'
come in line with the object, when steady the helm and note the course by compass
which will be the correct compass course to steer.
To find the distance a fixed light or object will be off when abeam when the
distance or range of the object or light is known, set the pivot of the vane G at B,
after taking a bearing of the light look on G for the number corresponding to the
range of the light the fore and aft line on A which this number cuts is the
distance the course being steered will take the ship off the object when it is on
the beam bearing; provided the ship is not set in or out. The athwart ship line
on A that the range number cuts is the distance the ship will have to travel on the
course being steered before the object will be abeam.
The card A may be made of transparent material to be illuminated from below,
or of metal or other suitable material and be illuminated from above; it may have
any suitable supports or clamps to fix it to the bridge rail or elsewhere; I may
also use gimbals so that it preserves its horizontal position like a compass, or 1
may gimbal it only for the rolling motion of the ship.
I may provide my graduated dial with two or more sight vanes, graduated or
otherwise, the pivots of which may be either fixed or movable along the base
line C. With certain modifications in construction to make it more portable
and easier for taking observations this instrument in conjunction with a compass
may be used for plotting in land surveying.
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 instrument consisting of a dial (A) the face of which is graduated
into equal parts representing square miles, or other standards of measurement,
fitted with sight vanes, (D, G,) graduated or otherwise, so that upon bearings
being taken with the instrument the dial answers the purpose of a chart, plotted
to square miles or other standards of measurements, and the portion of the
sight vanes extending across the face of the dial represents and does the same
work as bearings laid down on a chart, substantially as described.
2. In combination with a dial graduated as herein before described, a graduated
sight vane fixed to pivot on the centre of the circle produced and which may or
may not be made to slide along the base line of the instrument, substantially as
hereinbefore described.

page_text: 3. In combination with a dial graduated as hereinbefore described, two ог
more sight vanes either all attached to slide free so that their pivots are free to
move along the base line of the instrument, or some being fixtures and others
movable, for the purposes specified.
4. For purposes of land surveying the combination of a compass with the
graduated dial as specified.
5. The instrument hereinbefore described and illustrated on the accompanying
drawing for the purposes specified.
Dated this Fifth day of November 1891.
For the Applicant,
W. E. GEDGE,
Agent.