Note: Descriptions are shown in the official language in which they were submitted.
CA 02783767 2014-10-16
Measuring device
The invention relates to a measuring device, in particular for remote sensing,
the
measuring device having a measuring instrument and an apparatus for movable
mounting
of the measuring instrument.
In air-based remote sensing, the sensor system or, in general terms, the
measuring
instrument is usually directed vertically downward (nadir). Orthomosaic and
surface
models, for example, may be derived therefrom. A particular configuration is
seen in so
called oblique systems, which have at least one obliquely facing sensor (for
example a
matrix camera) (photogrammetric oblique aerial images with the Aerial Oblique
System
AOS, Albert Wiedemann, DGPF Tagungsband 18/2009). The data from such oriented
sensors can be used either to produce/improve orthophotos or for texturing
surfaces that
rise up (in particular building facades). There is an array of systems with
one or more
permanently mounted sensors that face in various directions. This approach
leads to a
significant conflict of aims: if the aim is to collect data with the lowest
possible outlay on
flying, the manufacturers increase the number of simultaneously active
sensors. There are
solutions that jointly drive one obliquely facing sensor, for example a
camera, each for all
four cardinal directions. The result of this is that the systems are large,
heavy and cost
intensive, and require correspondingly large platforms. Measuring systems with
fewer
sensors do not have these disadvantages to the same extent, but they do
require
substantially more outlay on flights so that the measurement provides areal
coverage.
Air-based remote sensing systems having moving sensors exist, inter alia, for
matrix
cameras. Because of their disadvantages to date, they are available only
sporadically, and
will be explained below.
A suspended camera system is, for example, Visionmap TM A3 (VisionMap A3 ¨ The
New
Digital Aerial Survey and Mapping System; M. Pechatnikow et al., FIG Working
Week
2009 Surveyors Key Role in Accelerated Development, Eilat, Israel, 3-8 May
2009), which
pivots about the roll axis of the aircraft. It is only the two oblique views
transverse to the
flight direction that are imaged in this case. Forward- and backward-facing
views and an
orientation between the cardinal direction axes are not possible. Such views
require
additional outlay on flights.
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An azimuthally movable camera system is, for example, Azicam TM from
GetMapping Plc.
(Getmapping Reveals New 'AZICAM' Oblique Camera System, Press Release June
2009). In this case, the obliquely facing camera is rotated by motor into one
of the four
cardinal directions. However, rotating the camera housing about the optical
axis has two
grave disadvantages. Firstly, without specific technical solutions cable
torsion renders
continuous rotation by 360 impossible, something which leads to time-
intensive
restoration to the initial position, and secondly the camera image undergoes
rotation by all
three possible angles 0.), 9 and K. This complicates the perspective
representation in the
photogrammetric process, since the image has to be rotated about its optical
axis (x). The
long azimuth shaft harbors a considerable distortion potential, something
which leads to
imprecise orientation with respect to an inertial navigation system and/or a
further camera.
Also known is a camera system that can be pivoted about the azimuth axis and
uses two
cameras. In this case, the principle of oblique view is that the two cameras
are arranged
on a vertical plane and have an angular offset. At one instant, a camera faces
obliquely
forward, and the second camera obliquely backward. By rotating the measurement
setup
by 90 , the cameras face in both directions transverse to the flight movement.
All four
cardinal directions are covered with the aid of two cameras in this way. The
problems
relating to continuous complete rotation (it takes time to stop the buildup
and to restart
backwards) and rotation by all three angles with the associated consequences
already
addressed are present here.
The invention is based on the technical problem of providing a measuring
device, in
particular for remote sensing, that can be used to attain various viewing
directions with a
low outlay on control.
The solution to the technical problem results from the subject matters having
the features
described hereafter.
In this case, the measuring device has a measuring instrument and an apparatus
for
movable mounting of the measuring instrument, the apparatus having two non-
parallel
rotation axes, the rotation axes not being the same as a longitudinal axis of
the measuring
instrument, the measuring instrument being connected to a rotatable drive
element via a
power transmission element. This permits a very simple and compact design, it
being
possible to move the drive element by a simple uniaxial drive, in order thus
to impart a
defined tumbling movement to the measuring instrument in the apparatus, that
is to say
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the longitudinal axis of the measuring instrument moves through a defined path
curve that,
depending on configuration, can be from zero to infinity. In the case of zero,
the drive
element is correspondingly not driven, and in that of infinity the drive
element executes a
complete revolution, thus producing a closed path curve, preferably a circular
path. In this
case, a rotation about the longitudinal axis of the measuring instrument is
avoided and, at
the same time, all relevant viewing directions are gone through. It may be
remarked at this
juncture that when the measuring instrument is a camera the longitudinal axis
is the same
as the optical axis.
In one embodiment, the apparatus comprises a universal joint in the case of
which the two
rotation axes are at right angles to one another. Universal joints have the
advantage of
being able to describe a tumbling movement very easily.
In one embodiment, the universal joint has a base suspension that has an inner
ring
mounted rotatably uniaxially, the inner ring bearing the measuring instrument
mounted
uniaxially. Here, the base suspension is preferably arranged rigidly on a
suitable platform,
for example in a flying device.
In a further embodiment, the drive element is designed as a drive disk.
The drive element is preferably permanently connected to a shaft that can be
driven
rotatably by a drive unit. Here, the drive unit is preferably arranged in an
immobile fashion
and outside the moving parts. This avoids a necessary balancing of mass as
well as
joining of cables by comparison with designs where a drive unit (motor) is
mounted on the
inner ring.
In a further embodiment, there is provided for the drive element a rigid guide
element that
prevents uncontrolled movements of the drive element and/or of the shaft.
In a further embodiment, the guide element is rigidly connected to the base
suspension.
By way of example it is also possible in principle for the guide element to be
fastened on
the rigid drive unit or on another rigid platform.
In a further embodiment, the measuring device has a sensor system for
detecting or
determining a rotation angle of the drive element, it being possible to
determine the angles
of the rotation axes from the rotation angle of the drive element, and to
determine the
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viewing direction of the measuring instrument therefrom. In this case, the
sensor system
can directly detect the angle on the drive element. However, it is also
possible,
alternatively or cumulatively, to detect the rotor position on the drive unit
and to infer from
the rotor position the angle of the shaft that is driving the drive element.
In a further embodiment, the power transmission element is designed as a rigid
connection. In this case, the connection must also be suitably guided during
the rotation of
the drive element. In one embodiment, the rigid connection is designed in this
case as a
connecting rod that is preferably connected to the drive element via a
spherical head
bearing.
In a further embodiment, the measuring instrument is designed as a camera.
In a further embodiment, the drive element executes an n x 3600 rotation, with
n> 1.
Because of the fact that cable torsion cannot come about, since the measuring
instrument
itself does not rotate, the drive element may be rotated continuously in one
direction.
Consequently, the measuring instrument also does not need to be braked in
order to be
able to return to its initial position. Consequently, the drive unit can be
designed with
smaller dimensions, and the energy requirement can be reduced, and this, in
turn, results
in a smaller and lighter overall system.
The invention is explained in more detail below with the aid of a preferred
exemplary
embodiment. The sole figure shows a perspective illustration of a measuring
device for
remote sensing.
The measuring device 1 comprises a measuring instrument 2 in the form of a
camera, and
an apparatus for movable mounting of the measuring instrument 2. To this end,
the
apparatus comprises a base suspension 3. The base suspension 3 is designed as
a
square or rectangular plate that has a preferably circular opening 4. An inner
ring 6 is
rotatably mounted on an inner edge 5 of the base suspension 3 via a first
rotation axis 7.
The measuring instrument 2 is rotatably mounted on an inner wall 8 of the
inner ring 6 via
a second rotation axis 9. The two rotation axes 7, 9 are in this case
perpendicular to one
another and form a universal joint. Furthermore, the measuring device 1 has a
drive
element 10 in the form of a drive disk. The drive disk is connected to a shaft
12 that can
be rotatably driven by a drive unit (not illustrated). By way of example, the
drive unit is
designed in this case as a stepping motor. The drive element 10 is therefore
also rotated
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by a rotation of the shaft 12. The shaft 12 is guided in this case by a guide
element 11 that
is arranged above the drive element 10. The guide element 11 is rigidly
connected in this
case to the base suspension 3 via connecting rods 13. Consequently, the guide
element
11 guides the shaft 12, on the one hand, and the drive element 10, on the
other hand. The
measuring instrument 2 is connected to the drive element 10 via a rigid
connecting rod 14
and a spherical head bearing 15, the connection being acentric. In this case,
the
connecting rod 14 is flush with the longitudinal axis of the measuring
instrument.
If the shaft 12 is now driven, the drive disk also rotates. This rotation is
then transmitted
via the connecting rod 13 to the measuring instrument 2, which carries out a
defined
tumbling movement in the universal joint, and so the viewing direction of the
measuring
instrument 2 likewise changes in a permanently defined fashion.
An evaluation unit (not illustrated) can in this case determine the respective
viewing
direction from the angular position of the shaft 12 or drive disk, since there
is a fixed
relationship between the angle of the shaft 12 and the angles on the rotation
axes 7, 9.
The viewing direction can in this case simultaneously be stored with the
recorded data of
the measuring instrument 2. However, it can also be provided to make
additional use of
sensor systems for detecting the angles of the rotation axes 7, 9, for example
in order to
detect the viewing direction more accurately, or for the purposes of
redundancy.
In addition to aerial photography flights with cameras of all types, the
measuring device
can also be used, for example, for 3D city modelling or mappings. By way of
example, the
measuring device can also be used for laser scanning or for acoustic pressure
investigations.
