Improvements in Surveying Instruments.
Year: 1896

page_text: Date of Application, 24th Mar.; 1896-Accepted, 24th Mar., 1897
Improvements in Surveying Instruments.
I, DONATUS RÖTHER of Weiden, Bavaria, in the Empire of Germany, Surveyor,
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 instrument allows an easy and direct reading off of the inclination of a
country and it may also be used as a handy level instrument and therefore may be
profitably employed for laying out roads, railroad revision and topographical survey
of all kinds.
In the accompanying drawings
Fig. 1 represents one part of the instrument, whilst Fig. 2 shows a second part
which in connection with the first one forms the complete instrument:
Fig. 3 is a mathematical diagram, and
Figs. 4 and 5 show the complete instrument in two other forms of construction.
On a suitable plate, as for instance shown in Fig. 1 there is fixed a spirit level A
and above the latter at an angle of 45 degrees to the axis of the level there is
fixed a mirror B having a horizontal line y cut across it. On the plate is also fixed
a scale C which is beneath and parallel to the axis of the level. This instrument
may be attached by a set screw D to the side of a staff which may be simply held 'or
may be stuck in the ground and if desired 'supported by a second staff so as to hold
it firmly. In the absence of a staff the instrument could be similarly fixed by a
thumb screw to a walking stick which could be held loosely between the fingers
the plate being caused to hang truly by tapping it lightly, and when level fastened
firmly by screwing up the thumb screw. Or it need not be screwed up tightly but
be left to freely balance itself it being made so that the scale C is horizontal when
the plate hangs freely at rest.
This device need be made in two sizes only the scales having divisions of 2 and
of 0-5 millimeters respectively. A concave mirror is used instead of a plane mirror
in the latter case in order to magnify the divisions which would otherwise be too
fine to be easily read.
To find the angle of inclination which a direct line from the observer to the point
observed bears to the horizon of the observer this instrument is either set up or held
and adjusted so that the centre of the level bubble and the zero of the scale C are
seen in the mirror as coinciding with each other and with the line y, this can only
occur when the spirit level is level horizontally and will only be seen by an
observer looking horizontally at the under surface of the mirror from the left side
of Fig. 1. Then without altering the position of the instrument the observer
raises or lowers his eye' until he brings the line y into line between his eye and the
point observed, that is to say he brings his eye into such position that the point
directly observed appears to him to coincide with the end of line y, there will then
be reflected in the mirror itself the scale C or part of it, and the division line read
at the intersection of line'y will give the angle of inclination:desired.
If however the observation be confined to keeping the centre of the level bubble,
the zero (or centre) of the scale C, and the line y in apparent coincidence in the
mirror, then 'any point observed which is also in apparent coincidence with the
line' y, will be actually on the same level horizontally as the line'y, so that
the instrument may be used as a level. The level is given with considerable

page_text: exactness and absence of liability to error of observation since no reading of the
scale is required but it is only necessary to observe that the distinctly marked zero
line of the scale coincides with the line y.
This instrument may be used for setting out or measuring on a gradient, if
employed in conjunction with a measuring tape or a staff of given length, without
plumbing and measuring in the horizontal plane. For this purpose there is
provided at the side of the main scale C a second scale or set of divisions so set
out that a reading of this scale may give the correction necessary to be made in the
measurement which has actually been made on the actual gradient of the ground,
so as to make it equivalent to,a measurement in the horizontal plane.
Thus when using a measuring tape of a given length, as for instance a chain, the
one end is attached to the staff carrying the instrument shown in Fig. 1, while the
other end of the tape is attached to a second staff which is of a length equal to
the distance from the line y to the foot of the first staff. The first staff being set
up and the tape stretched along the ground or parallel with the general incline
thereof, and the second staff set up at the end of the tape; an observation is taken
in the manner before described of the top of the second staff as if to find the
inclination thereto, that is to say the top of the second staff is brought into. visual
coincidence with the end of line y and the reading where the line y appears to
intersect the second or last mentioned scale is noted. This scale is so arranged for
the known length of the measuring tape that the number read off thereon may be
the measurement in any suitable unit, say inches or centimeters, of the additional
distance that must be measured off on the ground from the end of the tape to make
the measurement on the inclined plane or gradient equal to the projection of the
length of such tape measured in the horizontal plane.
Where in place of a measuring tape, a staff of predetermined height is used, for
instance a five-meter staff; there is added to the instrument a slide rule for finding
without delay or difficulty the distance of said staff, from observations giving the
angle of vision it subtends. Thus, Figure 3 shows a. diagram illustrating the
method; let a represent a five meter staff and a c an object of unknown height
at the same distance from the observers eye d, observations are then taken of the
three points a b and c and are as follows;
These calculations are however done on the calculating disk or slide rule at one
operation. The readings may be taken with sufficient exactness for many
purposes in practice and especially where speed is of more consequence than
minute accuracy.
The instrument that has been above described is suitable for all purposes or
observations based upon or involving the finding of angles in vertical planes; the
other part of the apparatus next to be described is used for such observations as
depend upon the finding or measuring of angles in the horizontal plane. This
apparatus is shown in Fig. 2. F is a base plate with straight sides parallel to each
other. On this base plate are fixed a compass G with magnetic needle and a
mirror H. The latter is inclined to the base plate at a suitable angle longitudinally
on the base plate, but so that any line imagined to be drawn across the mirror in a

page_text: plane parallel to the ends of the rectangular base plate will be parallel to the
surface of the base plate. Along near the lower edge of this mirror H is hinged
another mirror H¹.
On the mirrors H H are cut or made lines so that these lines are in a
plane perpendicular to the base plate F and parallel to the side edges of the
base plate. If now this instrument be held horizontal, with the end, on which
the compass is, directed towards a distant object, and the mirror H be viewed
from above, the reflection of the object from the mirror H¹ to the mirror H
will be seen by the observer, who can then turn the instrument in the
horizontal plane until the two lines xx appear to coincide with one another
and with the object; that is to say the coincidence of lines will depend
on the position of the observers eye which when these lines are seen in
coincidence will be vertically over them or in the same plane as the two lines,
and in such position the instrument may be carefully turned to bring the object
observed also into coincidence. The angle of the direction to said object with
regard to the magnetic pole can then be read off on the compass or represented by
a line drawn along the edge of the base plate F. This instrument is therefore
suitable for use in place of a prismatic compass or a surveyors sextant or for
quadradic surveys and generally for observations based upon the estimation of
angles in the horizontal plane.
By combining the two apparatus of Fig. 1 and Fig. 2 in one apparatus I have
therefore means for making both sets of observations. Two methods of combining
them are shown in the drawing in Figs. 4 and 5 respectively.
In Fig. 4, d' is a plate carrying the mirror B the level A and the circular slide
rule M together with the mirror H. Along the edge of plate d' is the plate C
provided with the divisions of the scale or scales (not shown). The plate F carries
the mirror H and the compass G, the latter being at the side of the mirror. The
side pieces a¹ b and another eide piece c¹ not shown, complete with the scale C
the sides of the case, of which the plates d and F form the lid and bottom
respectively.
The combination shown in Fig. 5 is substantially the same, only that the
mirror H is inclined in the other direction and the mirror H' is hinged at its foot
instead of being placed on the board d. is a hole for the screw D by which the
apparatus may be attached as aforesaid to a staff.
The angle of mirror H to the base plate is not material since even if the object
observed by above or below the level of the standpoint of the observer, it may be
brought into the field of the mirror by inclining more or less in the one or other
direction the mirror H'.
The two parts of the combined instrument are so made and connected that they
are disengageable one from the other.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. A Geodetic surveying instrument consisting of a folding box the one inside of
which contains a level and a scale below and parallel to the level, whilst above the
latter is arranged a mirror at a convenient angle (45°) to the axis of the level; said
box having on the inside of the other half a compass behind which is placed &
mirror ascending towards the compass, the lower rear edge of which mirror is
pivotally fixed to the edge of a second mirror turnable around this edge, substan-
tially as set forth and represented by Fig. 4.
2. A Geodetic surveying instrument, consisting of a folding booklike case as set
forth by Claim 1, the two folding leaves of which are disengageably connected with
one another, substantially as set forth.
3. A Geodetic surveying instrument consisting of a folding booklike case the one
inside of which contains a level and a measuring scale fixed below the level
parallel to its axis whilst above said level is provided a mirror whose reflector

page_text: plane forms a certain angle with the axis of the level whilst in the plane of said
inside is provided a second mirror, opposite to which in the plane of the other leaf
is provided a mirror and beside it a compass, substantially as set forth.,
4. The Geodetic instruments as set forth by Claims-1--3 7said mirrors! having
-concave,faces, substantiallylasi set forth.
HERBERT HADDAN & Co
18, Buckingham Street; Strand, London; WIC!,.
Agents for Applicant.