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John Adolphus Flemer.

An elementary treatise on phototopographic methods and instruments, including a concise review of executed phototopographic surveys and of publicatins on this subject online

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Online LibraryJohn Adolphus FlemerAn elementary treatise on phototopographic methods and instruments, including a concise review of executed phototopographic surveys and of publicatins on this subject → online text (page 18 of 33)
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The photographic plates are 18X24 cm., which is the same
size as for the older instrument, model 1884.

The objective lens, at first selected, was an aplanat of Stein-
heil, and it had a focal length of 237.7 mm. More recently,
however, the Italian phototheodolites have been supplied with
anastigmatic lenses of Zeiss.

The column E, Figs. 117-119, Plates LVI and LVIII, forming
a prolongation of the lower arm /'g', is held in place by two
counter screws m and m', which serve to hold the horizontal axis
of rotation of the camera in a fixed position, preventing accidental
changes that might otherwise take place during the execution of a
set of panorama pictures.

By unscrewing the nuts d', Fig. 120, Plate LIX, the tripod
legs may be removed and they may then serve as " alpenstocks "
during the transportation of the instrument from station to sta-
tion. The " camera telescope " may be lifted out of the Y's and
packed separately, the lower part of the instrument the sub-



SURVEYING-CAMERAS AND GEODETIC INSTRUMENTS. 223

structure is packed in another carrying-case, while the plate-
holders and plates are transported in a third case.

C. L. P. Paganini's Photographic Azimuth Compass (Photo-
graphic " Azimutale").

During the last years of Paganini's service as an officer in the
Royal Navy of Italy, while in command of the cruiser " Tripolis,"
he was engaged upon work connected with making descriptions
of the coast ( u coast-pilot work"), and with hydrographic surveys
for the construction of harbor and sailing charts. This work,
undertaken for the production of better navigation guides, en-
tailed a minute study of the approaches from the sea and a
thorough reconnaissance of the coastal belt of topography.

Landmarks available and useful for sailing-guides were to be
accurately determined and plotted upon the hydrographic charts.
Paganini was particularly instructed to obtain pictorial views of
certain coast regions, showing the appearance of the coast when
viewed from certain points off shore and giving the magnetic
bearings to certain reference points shown on the views from the
points marked on the charts whence the views were obtained.
The point of view was determined either by means of the three-
point problem or it was indicated by means of the estimated
distance from some well-defined landmark (lighthouse or other
prominent object) giving also the magnetic bearing.

The perspectives used to illustrate parts of the coasts, in order
to facilitate the identification of the " landfall " by mariners
when approaching the coast from the open sea, were published
either on the charts or in so-called coast-pilot books. Formerly
they were obtained by drawing a free-hand perspective from the
deck of a vessel, including all prominent features and sailors'
landmarks, particularly lighthouses, lone trees, prominent bluffs,
and other characteristic features or marks.

Such perspectives (Beautemps-Beaupre* and Porro had a
remarkable skill in producting accurate perspectives of such



224 PHOTOTOPOGRAPHIC METHODS AND INSTRUMENTS.

terrene views by offhand sketching) could not be made with
mathematical precision, and very few draughtsmen have the gift
to draw these perspectives under such conditions rapidly and of
uniform scale. Their subsequent reduction to paper, under
application of empirical and often arbitrary rules, based on sex-
tant angles, magnetic bearings, and the mentioned defects in the
sketches, had but a doubtful value, particularly if the vessel,
during the time period which was consumed while these various
observations were made, had gradually changed its position, due
to winds and sea currents.

Paganini, fully appreciating these difficulties, soon recognized
the value of photography for obtaining such perspectives more
readily and far more accurately, if a suitable photographic instru-
ment could be constructed to be used on shipboard, the use of
an ordinary camera, of course, being precluded.

For several years Paganini made studies and experiments
with the above object in view, particularly since the instantaneous
photographic process had been perfected, and the photographic
azimuth compass ("azimutale fotografico ") is the direct result
of his labors in this direction. It was devised to subserve the
demands touched upon in the preceding paragraphs, and the
instrument, described in Paganini's "De nuovi Appunti," has
been made by Galileo in Florence.

This instrument may serve to locate with accuracy lighthouses,
buoys, and rocks awash, to obtain topo- and hydrographic views 6f
the coast (for coast, harbor, and wharf surveys) for explorations
and scientific expeditions, for the survey of unexplored coastal
belts, for naval reconnaissance, for picturing naval displays and
engagements, etc. It is furthermore adapted to determine the
geographical latitude of a vessel's position by photographing the
altitude of the sun above the sea horizon, including its magnetic
bearing at the moment of the plate's exposure. From a negative
showing the image of both the sun and the sea horizon the
declination and the azimuth (magnetic) of the sun may be de-
duced, and the time being known when the plate was exposed,



SURVEYING- CAMERAS AND GEODETIC INSTRUMENTS. 225

the geographic position of the camera may be deduced from the
plate.

Paganini's photographic azimuth compass is shown, in a
general way, in Figs. 130 to 133, Plates LXV to LXVIII. The
photographic plates are exposed in this instrument with the long
sides (24 cm.) horizontal and the short sides (18 cm.) vertical.

The objective is very similar in arrangement to that described
for the Italian phototheodolite, having a graduated scale to enable
the observer to obtain the focal length directly. The two cross-
wires, with their point of intersection in the optical axis of the lens,
are secured in the image plane, the same as with the phototheo-
dolite.

The camera-box C is supported by two upright pieces 5, shaped
like an inverted U; at the top they are united by a horizontal plate
Z, extending from the two camera sides around to the front of the
camera, forming a horizontal connection in the shape of a horse-
shoe. Three projections d, one at the front and two at the sides
of the camera, serve to support the camera-box upon the horizontal
frame Z by means of three pairs of counter screws v. In the
sectional view of the instrument, Fig. 133, Plate LXVIII, r indicates
the vertical axis of rotation, gg the horizontal circle, B the azimuth
or ship's compass, VV leveling-screws (supporting the horizontal
circle on the heavy plate TT), Q a heavy weight (to lower the
center of gravity of the apparatus and to increase the stability of
the same when used on the deck of a rolling vessel), m is the
handle of central screw (clamp) which passes through Q and enters
a spherical nut attached below the horizontal circle, to allow for
lateral swing when leveling the camera with the foot screws V.

When this instrument is used on land the gimbal support is
replaced by a special surveying- tripod, the instrument resting on
the latter by means of the three leveling-screws V. The illustra-
tions show the instrument with the gimbal support the way it is
used on shipboard. The three leveling-screws V rest upon a
plate TT which is connected with the stout ring A by gimbals,
the ring A in turn being supported by . four stout legs. The



226 PHOTOTOPOGRAPHIC METHODS AND INSTRUMENTS.

weight Q is sufficiently heavy to assure the vertical axis of rotation
r, Fig. 133, Plate LXVIII, to remain always vertical. This
apparatus is best adjusted and tested on shore, in order to adjust
the horizontal thread OO f by means of the sea horizon.

Below the under side of the camera-box (the latter is inclined
about 30) another smaller camera c is placed, .close to the middle
of the rear end, having a prism attachment by means of which a
section of the compass graduation is reflected upon the lower edge
of the photographic plate, the pictured graduation extending to
both sides of the pictured principal line //', as indicated in Fig. 134,
Plate LXVIII. The shutters of both cameras, C and c, are
operated simultaneously by pressing the rubber bulb 6, Fig. 132,
Plate LXVII. The rubber tube attached to the bulb is forked,
a separate branch leading to each pneumatic shutter, as indicated
in Fig. 132. The optical axes of the cameras are at right angles
to each other and both are in the vertical plane containing the
principal line //'.

The diameter of the dial compass passing through the zero
mark of the graduation is identical with the magnetic meridian,
and the compass-reading, designated by the graduation mark
that is bisected by the prolonged vertical thread //' below the
picture, represents the magnetic azimuth of the optical axis of
the instrument at the moment of the exposure, or it will indicate
the angle of orientation for the picture. The vertical frame E,
Figs. 132 and 133, Plates LXVII and LXVIII, has a set of cross-
wires with their point of intersection in the vertical plane which
passes through the optical axis of the camera. A peep-hole O T
also situated in the vertical plane passing through the optical
axis of the camera, is affixed to the upper horizontal limb, and
with the cross- wires in E t it will enable the observer to direct the
camera to any point that is to be bisected by the principal line
when a plate is exposed.

Also this instrument is provided with a Zeiss anastigmat lens
of 250 mm. focal length. Eastmann's films or plates are used
(18X24 cm.) and the horizon may be covered by eight plates,



SURVEYING -CAMERAS AND GEODETIC INSTRUMENTS. 227

allowing a liberal marginal overlap, each plate covering an angle
of about 50 horizontally.

D. Plwtogrammetric Theodolite of Pro). S. Finsterwalder.

This phototheodolite, devised by Prof. S. Finsterwalder after
many years of practical work and experience, gained in his alpine
surveys and studies of glacial motion, has been constructed by
Max Ott (A. Ott), Kempteri, Bavaria. In the pursuance of this
work Prof. Finsterwalder early recognized the desirability of a
surveying- camera of compact build, rigidly constructed in all
its parts and yet having a minimum of weight. To avoid the
transportation of a separate transit or theodolite for the trig-
onometric location of the selected camera stations, he provided
the surveying-camera with means for observing horizontal and
vertical angles.

This phototheodolite is represented in Fig. 135, Pate LXIX,
and the total weight of the outfit, 10 kgr., is distributed as follows r
The instrument itself weighs 2.7 kgr., its carrying case 2.4 kgr., the
tripod 1.7 kgr., one dozen leather receptacles, including twelve
photographic plates 2.5 kgr., and the packing-case for the latter

0.7 kgr.

Prof. Finsterwalder has used both an anastigmat lens of Zeiss
and a double anastigmat of Goerz, with a focal length of 150 mm.
With this focus the lens will photograph perspectively correct a
plate of 160X200 mm. The plates used are 120X160 mm.,
giving an effective horizontal field of 53, enabling the observer
to cover the entire panorama with seven plates.

For the central or normal position of the objective this camera
commands an effective vertical field of +20 and 20, or 40
in all. Twenty degrees above or below the horizon of the camera
station would often be insufficient, particularly, when working in
mountainous terrene. It was deemed advisable, therefore, to
mount the objective on a slide, permitting considerable change
in the vertical sense. Owing to this device objects subtending



228 PHOTOTOPOGRAPHIC METHODS AND INSTRUMENTS.

angles of depression up to 35 (together with a vertical angle of
elevation of 5) may still be photographed on the vertical plate.

In extreme cases, when it should become desirable to photo-
graph objects subtending angles of +35 and 35 (or 70 in all),
Prof. Finsterwalder recommends the successive exposure of two
plates, one with the maximum elevation and the other with the
maximum depression of the lens. Inclined plate-pictures are
thus not only avoided but the effective plate surface is utilized to
the fullest extent and the weight of the glass to be carried is
reduced to its minimum.

In order to obtain uniformly accurate and trustworthy results
with the relatively short focal length, maintaining a constant
distance between the lens and the sensitized surface of the plates,
the latter are not placed into plate-holders of the usual pattern
(where the variable thickness of the glass plates would affect the
so-called "constant" focal length), but they are pressed against
a metal frame instead, which frame forms the back of the camera-
box, an arrangement very similar to that of Capt. E. Deville's
camera. To insert the plate into the camera use has been made
of Dr. Neuhauss's leather plate-holders, formed like a sack, B,
Fig. 135, Plate LXIX. The inner edges of the metal frame are
graduated in order to locate the principal and horizon lines upon
the negatives.

These leather sacks have metal slot devices facilitating the
transfer of the plates from the sacks to the camera and vice versa.
By hooking the mouth of the sack to the upper edge of the rear
camera side and opening the slot while holding the bag in a
vertical position, the plate is allowed to slip from the sack into
the carrier. Springs attached to the rear of the camera-box
serve to check the sliding plate and prevent a too sudden drop of
the same into the metal carrier where the plate is to be exposed.
These springs also press the plate into perfect contact with the
metal frame at the back of the camera- box when once in
position.

By withdrawing the upper curved handle (Fig. 135, Plate



SURVEYING-CAMERAS AND GEODETIC INSTRUMENTS. 229

LXIX) at the back of the camera the tension of the springs may
be reduced (or their action may be released entirely), when the
plate will glide into position for exposure. After exposure the
lower slide is withdrawn and the tension of the springs is again
reduced, when the plate will slip into the empty sack B, which
had been hooked to the lower ^edge of the rear camera side as
shown in Fig. 135, Plate LXIX.

The eccentricity of the center of gravity, by applying the weight
of the sack, including plate, to one side of the camera, does not
affect the general adjustments of the instrument sufficiently to
throw the photographic plate out of the vertical plane when the
exposure is made.

The camera is accurately balanced when no sack is attached,
in which form it is used to measure the angles that may be
required for locating the camera station, both in the geographical
and vertical sense, with reference to the trigonometric signals
in the vicinity.

In order to use this instrument as a transit the back of the
camera is supplied with an eyepiece E, Fig. 135, Plate LXIX,
of a magnifying power of from 7 to 8, forming a centrally mounted
telescope with the camera objective O. The eyepiece is supplied
with a cap or shutter to exclude the light when the instrument is
used for photographing. A diaphragm with the usual cross-hairs
is also attached to the eyepiece.

The camera-lens (or the objective of the camera telescope)
being movable in the vertical sense within a range of 100 mm.,
all objects falling within a vertical range of 17 may be bisected
with the telescope. The definition of points to be bisected, when
above or below the camera horizon, would become very poor if
the eyepiece E were rigidly fixed in a horizontal position by
means of the arms NN, Fig. 135, Plate LXIX. However, it may
be revolved about a horizontal axis in such way that it will always
be directed toward the center of the camera-lens.

With the double anastigmat of Goerz, which produces a per-
fectly flat picture, with neither spherical, chromatic, nor astig-



230 PHOTOTOPOGRAPHIC METHODS AND INSTRUMENTS.

matic distortion, a change in the focus of the eyepiece will
rarely be necessary.

Horizontal angles may be observed directly by means of a
horizontal circle H of 120 mm. diameter, which is provided with
two verniers reading to single minutes. Experimental tests
made with this instrument have shown that horizontal angles
between points of considerable difference in altitude may be
observed within a limit of error of 0.4'. This instrument, there-
fore, gives results sufficiently accurate to locate the camera stations
trigonometrically with reference to surrounding fixed points of
known positions, provided they are not too far distant to be
defined with this low-power camera telescope.

Vertical angles, however, cannot be measured directly; still,
by means of the scale and vernier attached to 'the lens slide or
front board of the camera, changes of the objective from its
central or normal position values directly proportional to the
trigonometric tangents of the vertical angles may be read to
0.05 mm. The slide motion of the front board is accomplished
by means of a rack and pinion, and experience has proven that
vertical angles may be observed with this device within a limit of
of error (converted into arc. measure) of i'.

The three rods designated by h in Fig. 135, Plate PXIX, are
100 mm. long and they serve to elevate the instrument support,
together with the three leveling-screws 5, sufficiently high above
the tripod legs to allow full play for the leather plate-holders B, when
they are placed in position to receive the exposed plate. The tri-
pod legs may be folded to half their lengths. No ground glass
being provided, a special finder has been devised correctly show-
ing the field controlled by the plate (in both the vertical and
horizontal sense) for any position of the camera-lens. (Zeitschrift
fur Instrumentenkunde, Oct., 1895.)



SURVEYING-CAMERAS AND GEODETIC INSTRUMENTS. 231

E. Phototheodolite for Precise Work by O. Ney.

In the construction of this instrument, Figs. 136 and 137, Plates
LXX and LXXI, it has been sought to fulfill the following
requirements:

First. The camera should be dimensioned for the exposure of
plates sufficiently large to produce clearly defined perspec-
tives.

Second. The general disposition of weight and mass should be
symmetrical. Both camera and telescope are to be mounted
centrally.

Third. The total weight of the instrument is to be reduced to

the minimum consistent with rigidity and sufficient strength

to assure stability and permanency of its adjustments when

used in the field. The integral parts are to be formed

to permit a free and easy manipulation of the instrument.

Ney's instrument is composed of two distinct parts the

camera proper and the transit theodolite which may be used

successively and independently one of the other, but always upon

the same tripod. The interchange between the two is readily

accomplished with accuracy and expediency.

The principal advantages attached to this disposition of the
component parts of Ney's phototheodolite may be cited as follows :
First. The symmetrical and central mounting of the camera
and transit telescope will insure permanency hi the adjust-
ments with consequent accuracy in the results.
Second. By using the same tripod and horizontal circle T,
Figs. 136 and 137, Plates LXX and LXXI, for both
camera and transit their individual weight has been reduced
to a minimum.

Third. A possible disturbance of the adjustments of the instru-
ment support D and tripod may be guarded against by hav-
ing the plate inserted and the slide withdrawn before placing
the camera- box in position on the upper alidade limb A,
Figs. 136 and 137, Plates LXX and LXXI.



232 PHOTOTOPOGRAPHIC METHODS AND INSTRUMENTS.

Accuracy and ease in the manipulation of this instrument
have been assured by supplying all leveling- and clamp -
screws with spherical ends which rest upon suitable plates in
such a manner that a free play of motion will take place. These
spherical terminations of the screws were originally devised by
Reichel.

Fig. 136, Plate LXX, illustrates the phototopographic camera
mounted for use. Fig. 137, Plate LXXI, represents the transit
with a striding compass B.

D is the very rigid, yet essentially light, instrument support.
The three arms supported by leveling screws are cast in one piece
with the bearing for the conical pivot, which in turn is securely
attached to the alidade T. The instrument support Z>, horizontal
limb T, upper alidade limb A, together with the skeleton tripod,
are used in common for both transit and camera.

A large circular level R is permanently secured to the center of
the upper alidade limb A.

Three hardened plates are inserted into the upper surface of A
at S. One has a plane surface, the second has a conical cavity, and
the third is provided with a V-shaped slot or groove ; they receive
the spherical ends of the three screws which support the transit
and the camera.

The horizon lines of both instruments may be adjusted and
brought into the same horizontal plane by means of these sets of
three screws each, which are attached to the base of both camera
and transit.

Either instrument may be securely bound to the common
support A by turning the horseshoe-shaped clasps C, hinged ta
A t over the ends of the three screws and giving the levers E a
quarter-turn.

The transit telescope is arranged for stadia-reading (after
Porro's method), having 100 as the common multiplier. The
telescope-level is graduated to 20".

The compass graduation reads to 30' and the horizontal circle
reads either to 10" or 20", according to the size of the instrument.



SURVEYING-CAMERAS AND GEODETIC INSTRUMENTS. 233

The larger class instrument has plates 18X24 cm. and the small-
sized camera has plates 13X18 cm.

To avoid changes in the dimensions of the camera-box due to
hygroscopical influences of the atmosphere it is constructed
entirely of aluminum. The plate -holders and the movable carrier
are made of mahogany impregnated with paraffine to render the
wood impervious against moisture.

To avoid any possible change in the constant focal length,
due to any uneven thickness of the plate-holders or of the photo-
graphic glass plates, the carrier may be moved forward in the
direction of the camera axis by means of the levers H y Fig. 136,
Plate LXX, until the sensitized -film surface is brought into direct
contact with a metal frame securely fastened to the walls of
the camera. This frame has a centimeter graduation filed into
its inner edges, and the distance of the rear surface of the frame
from the nodal point of the camera-lens constitutes the constant
focal length of the camera.

The centimeter graduation on the inner edges of the metal
frame, reproduced on the margins of the negatives, serves a double
purpose. By its means the principal and the horizon line may
be drawn on the face of each negative, and it also serves to ascertain
whether the sensitized films, or the paper prints, have under-
gone any change in dimension during the process of development.
If distortion has taken place the amount of correction to be applied
to the print may readily be found.

The camera is provided with a pair of cross-levels to enable
the observer to detect any change in its adjustment before expos-
ing a plate. These levels have a graduation corresponding to
20" of arc.

When the instrument is in perfect adjustment, the picture
plane will be vertical and the principal ray will be in the same
horizontal plane as the optical axis of the horizontal telescope
if the camera were replaced by the transit (without disturbing
the position .of the tripod and instrument support).

When this camera theodolite is adjusted the vernier M, Fig. 136,



234 PHOTOTOPOGRAPHIC METHODS AND INSTRUMENTS.

Plate LXX, will read zero for the normal position of the lens.
The objective may, however, be elevated or depressed by 35 mm.,
and any change from its normal position may be read correctly
within o.i mm. on the scale and vernier M.

The pneumatic camera-shutter is arranged for either time
or instantaneous exposures; a special device guards against
the possibility of exposing a plate before it is brought into per-
fect contact with the graduated- metal frame. Neither can the
plate-holder be withdrawn from the camera before the slide
has been replaced nor as long as the plate is in contact with
the graduated frame. (Zeitschrift fur Instrumentenkunde, 1895,

P- 55-)

F. Phototheodolite of Dr. C. Koppe.

Dr. Koppe, Professor at the Technical High School in Bruns-
wick, Germany, is an ardent advocate of photogrammetry and
he has done much toward popularizing photographic surveying



Online LibraryJohn Adolphus FlemerAn elementary treatise on phototopographic methods and instruments, including a concise review of executed phototopographic surveys and of publicatins on this subject → online text (page 18 of 33)