An Improved Method of Range Finding.
Year: 1890

page_text: Date of Application, 31st July, 1890
Complete Specification Left, 28th Mar., 1891-Accepted, 11th-July, 1891.
PROVISIONAL SPECIFICATION.
An Improved Method of Range Finding.
I, THOMAS SCULLY of 44 Harcourt Street Dublin, Ireland, Civil Engineer do
hereby declare the nature of this invention to be as follows:-
The object of my invention is to produce a simple and effectual method of
range finding, or distance estimating; and is especially applicable for military.
purposes.
My invention is based on the principle of direct comparison of standard real
objects, or images whose appearances, and real heights correspond with the
observed appearances and apparent heights of similar objects viewed at known
distances.
The invention consists in fixing in an ordinary telescope, or other suitable object
viewing instrument a transparent diagram showing a series of required standard
objects, or images suitably disposed for comparison and in such a position that the
figures of the diagram shall coincide with the real images of the distant observed
objects as formed by the object glass of the telescope. Or the transparent diagram
may be otherwise suitably arranged to meet the requirements of the particular kind
of object viewing instrument used.
Dated this 29th day of July 1890.
J. K. FAHIE & SON,
9, Westland Row, Dublin, Agents for Applicant.
COMPLETE SPECIFICATION.
An Improved Method of Range Finding.
I THOMAS SCULLY, Civil Engineer, residing at 11, Grantham Street, S.C.R.
Dublin, 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 :-
My invention consists in principle in the direct. comparison, as to linear
dimensions of standard objects or images with the apparent linear dimensions of
observed distant objects or the images thereof with a view to determine their
distance from the observer.
And in application by inserting a transparent diaphragm bearing such standard
objects or images in a telescope in such a manner that the said standard objects or
images may be viewed distinctly & concurrently with the observed distant objects
or the images thereof, or by any arrangement optical or otherwise, bringing about
such a comparison of standard objects or images with the apparent relative sizes of
observed distant objects or the images thereof, with a view to determine their
distance.
The following illustration will serve to show the practical application of the
invention.
Let the objects, whose distance it is required to determine be soldiers in the field,
prepare a diagram to any scale such as I herewith furnish showing the relative sizes
of a man of any assigned height viewed at different distances as indicated by the
numbers over each man or group of men (the single figures show the distance in so
many hundred yards, 4, 5 &c. = 400 yds. 500 yds. &c. &c. & in other cases it is
stated in full as 2500 = 2500 yds. &c. &c.) (such a diagram is easy to construct
for, if any height be assumed to represent apparent height of man at initial
distance height for any other distance is simply inversely as that distance). Now
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calculate the size of image of a man of any assigned height (5' 8" is best) & any
given distance, formed by the object glass of any particular telescope (from
formula 1 +
& reduce the diaphragm photographically on a piece of
thin glass & insert it in the telescope to coincide with said image & to such a scale
that the size of the figures in the diaphragm corresponding to the distances at
which the real man is viewed may be equal to the image of the real man formed by
the object glass then according as the man is viewed at different distances, his
image will coincide with the figures in the diaphragm corresponding to these
distances, & conversely the process will give his distance, when his image as seen
thro' the telescope is duly allocated in the diagram.
Having now particularly described & ascertained the nature of my said inven-
tion & in what manner the same is to be performed, I declare that what l
claim is
That thro' the peculiar feature of the principle being graphic it minimizes the
great objection to such instruments as measure distances by comparing height or
one dimension only, which method tho sound in theory, fail in practice generally
as for instance in the case of a man whose jeet were hidden by an object. Whereas
with my device even if only half his body were visible it would give a very close
idea of his proper allocation in the diagram the eye instinctively sizing the object
while only viewing part of it.
Dated this 27th day of April 1891.
THOMAS SCULLY, C.E.