Television – Special applications – Object or scene measurement
Reexamination Certificate
2000-05-15
2004-05-04
Philippe, Gims (Department: 2613)
Television
Special applications
Object or scene measurement
C701S207000, C702S104000
Reexamination Certificate
active
06731329
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
The invention is directed to a method and an arrangement for determining the spatial coordinates of at least one object point through video measurement image tachymetry, preferably for use in geodesy and also in building surveying and object surveying.
b) Description of the Related Art
Modern electronic tachymeters have an arrangement for automatic fine target seeking. In the first step, assuming the presence of image evaluation electronics, they would enable the storage of the target image for supplementing the measurement data of the tachymeter comprising the distance to the target point marked by a reflector, the horizontal angle and the vertical angle. The entire surrounding field of the measurement point can accordingly be fixed in the digital image. This would be the video tachymeter in its simplest form. The precondition for this is that the object field or the object is located, in the horizontal direction, virtually vertical to the optical axis of the video tachymeter and that all objects appear simultaneously sharp in the target image. Likewise, the sighting must be virtually horizontal.
An arrangement of a “video tachymeter” is indicated in DE 36 28 350. In this reference, the reflector is photographed by a video camera arranged on a tachymeter with a point number label to supplement the measurement value of the tachymeter with the added information, that is, the point number. Thus, in this case, additional information is collected which is only used to improve documentation of the terrain points to be measured. Measurements of the terrain points based on the recorded images are not possible with this arrangement.
DE 198 00 336 shows another simple arrangement with an entirely different purpose. In this case, a sensor measuring unit for measuring distances is located on the camera. Data for the orientation of the camera to the object are collected by this arrangement and employed digitally. The measurement values of the camera accordingly maintain an absolute orientation.
WO 97/36147 is likewise directed to the orientation of a video camera to a scene as an object with three selected points whose position is known. Data from the recorded images are used for determining the position of the camera.
DE 196 04 018 is directed to an entirely different object. The arrangement comprises a theodolite with a target pointer and a laser beam distance meter mounted thereon for distance measurement without reflectors. The distance to the surface of the object is measured and the edges of the same are sighted with the telescope, and the angular position of the object is determined. The width of the object can be calculated from the distance and the angle. This reference does not concern a video tachymeter. Measurement values of the object are calculated from the determined measurement data of the theodolite and distance meter by means of a computer. A recording of an image of the object to be measured and determination of measurement data of the object from this image are not carried out.
In EP 0 417 125 B1 (DE 689 04 911 T2), the correlation of three point with surfaces of rooms or spaces is determined with a similar arrangement via these three points by measuring distances and angles. When a plurality of surfaces are measured, lines of intersection and corner points can be determined depending on the quantity of measured surfaces. Here also, no images of the room to be measured are recorded and no measurement data are obtained therefrom.
Arrangements for distance measurement and focusing in photographic cameras do not satisfy the strict requirements for accuracy in geodesy.
In the informational publication “Surveyor™ ALS with Video Option” by the company MDL, a terrain image of an object in the form of terrain is digitally composed from spatially oriented and positioned video pictures by means of a digital video camera and measurement is carried out by means of polar data (distance and angle) which are determined by a normal tachymeter. This digital terrain image has plan information and height information; the latter is determined, and then displayed, in the form of contour lines by means of geometric calculation as is conventional in the making of plans and maps. Dimensional calculations and terrain models can then be derived with the help of these data. Since a distance meter without reflectors is involved, according to this publication, open terrain can be surveyed from an elevated viewing point or stand point without inspection on foot. This is an advantageous application variant of video tachymetry. Unfortunately, it has only very limited accuracy.
To summarize, it can be stated that in the cited prior art:
no measurements are carried out in the video image,
there is no combination of the video image data with the data of the tachymeter and/or theodolites such as distances, horizontal angles and vertical angles,
no data are derived from these direct measurement data,
and no video tachymetry is undertaken.
The object of the EV consists in obtaining and utilizing measurement data from the stored target image for determining additional object points. For this purpose, a plurality of base points marked by reflectors are determined in the video image, wherein distances and angles relative to these base points are measured centrically subsequently in order to determine measurement points between the marked base points from the measurement data of the video image during a subsequent home evaluation of the measurement data and measurement images. At great distances, all images appear sharp almost simultaneously. In order to detect the marked object point in a sharp surrounding area at shorter sighting distances at which the objects extend depthwise, transformation is carried out on this image with maximum contrast proceeding from the images of the base points. In this way, an accurate marking of the desired object point is possible. For this reason, the digital image must have the quality of a measurement image. Because of this possibility, it is possible when recording the terrain to limit to a few critical points which simultaneously form the base points in order to determine additional object points from the video image during the homebase working phase, the positions of these object points being derived computationally from the base points. These object points can be marked during the recording as well as afterwards in the video image by means of a mouse. This possibility saves time when recording in the field and it permits the spatial recording to be supplemented without subsequent footwork or additional field comparison.
OBJECT AND SUMMARY OF THE INVENTION
Accordingly, it is the primary object of the invention to provide a method and an arrangement for video measurement image tachymetry by which measurement data can be obtained from the recorded target image for effectively determining the position of object points and which reduces expenditure on geodetic measurements.
According to the invention, this object is met by a method for determining the spatial coordinates of at least one object point P
i
from the coordinates of at least two base points which serve as reference points and which do not lie in a plane by a video tachymeter which is arranged at a recording stand point, is swivelable about a vertical axis StA and comprises a distance measuring arrangement, a video camera with CCD matrix, a sighting device and angle measuring devices, wherein the video camera is tiltable about a horizontal axis. The method includes the steps of marking the base points B
1
; B
2
in the terrain and sighted by the sighting device, measuring their coordinates by the distance measuring arrangement and angle measuring devices, additionally recording a target image M′
1
; M′
2
containing the marked base points B
1
; B
2
and the object points P
i
by the video camera and storing the target image and determining the coordinates of the object points P
i
from their image point coordinates in the target images M′
1
; M
Feist Wieland
Monz Ludwin-Heinz
Seeber Marcel
Philippe Gims
ZSP Geodaetische Systeme GmbH
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