66,494 research outputs found
Influence of photogrammetric dynamic movements of non â metric camera on the accuracy results in digital images processing
Real-time photogrammetry is used for the registration and control of object structure and deformations, registration of dynamic processes, particularly, in the architectural heritage objects. The main product of the photogrammetry is a three-dimensional (3D) data â real world vision at the time the images are acquired with fixed viewing angles. In order to achieve this result a lot of digital photogrammetric workstations (DPW) were designed. A wide range of digital imagery such as scanned aerial film frames, images from digital aerial cameras as well as images from various satellite sensors could be processed using DPW. The requirements of processing, the algorithms of the photogrammetric software systems for the dynamic line-by-line acquisition processing of digital images in the photogrammetric way differ according to the applications. Therefore, it is important to test the capabilities and data accuracy of more than one digital photogrammetric system. The images of the research object were taken by a digital nonmetric camera Canon EOS 1D Mark III. The quality of images depends on the camera optical system errors (calibration parameters) and camera stability - dynamic movements during images exposure. Thus, it is necessary to test calibration results and camera positions during the image exposure time. In this case, the camera was recalibrated and the new calibration parameters were checked during the images processing. Values that define camera stability and dynamics were determined. Close-range digital images were processed â the triangulation procedure was accomplished by using digital photogrammetric software PhotoMod and Inpho as well as DPW system Bluh. The accuracy of triangulation has been tested and compared with the manufacturerâs software
The QUEST Data Processing Software Pipeline
A program that we call the QUEST Data Processing Software Pipeline has been
written to process the large volumes of data produced by the QUEST camera on
the Samuel Oschin Schmidt Telescope at the Palomar Observatory. The program
carries out both aperture and PSF photometry, combines data from different
repeated observations of the same portion of sky, and produces a Master Object
Catalog. A rough calibration of the data is carried out. This program, as well
as the calibration procedures and quality checks on the output are described.Comment: 17 pages, 1 table, 8 figure
Reconstruction of hidden 3D shapes using diffuse reflections
We analyze multi-bounce propagation of light in an unknown hidden volume and
demonstrate that the reflected light contains sufficient information to recover
the 3D structure of the hidden scene. We formulate the forward and inverse
theory of secondary and tertiary scattering reflection using ideas from energy
front propagation and tomography. We show that using careful choice of
approximations, such as Fresnel approximation, greatly simplifies this problem
and the inversion can be achieved via a backpropagation process. We provide a
theoretical analysis of the invertibility, uniqueness and choices of
space-time-angle dimensions using synthetic examples. We show that a 2D streak
camera can be used to discover and reconstruct hidden geometry. Using a 1D high
speed time of flight camera, we show that our method can be used recover 3D
shapes of objects "around the corner"
A flux calibration method for remote sensing satellites using stars
Star surveys and model analyses show that many stars have absolute stable
fluxes as good as 3% in 0.3-35{\mu}m wavebands and about 1% in the visible
wavebands. The relative flux calibrations between stars are better than 0.2%.
Some stars have extremely stable fluxes and can be used as long term flux
calibration sources. Stellar brightness is several orders of magnitude lower
than most ground objects while the stars do not usually appear in remote
sensing cameras, which makes the stars inappropriate for being calibration
sources. The calibration method using stars discussed in this paper is through
a mini-camera attached to remote sensing satellite. The mini-camera works at
similar wavebands as the remote sensing cameras and it can observe the stars
and the ground objects alternatively. High signal-to-noise ratio is achieved
for the relatively faint stars through longer exposure time. Simultaneous
precise cross-calibration is obtained as the mini-camera and remote sensing
cameras look at the ground objects at the same time. The fluxes from the stars
used as calibration standards are transferred to the remote sensing cameras
through this procedure. Analysis shows that a 2% accurate calibration is
possible.Comment: 12 page
Separating true range measurements from multi-path and scattering interference in commercial range cameras
Time-of-flight range cameras acquire a three-dimensional image of a scene simultaneously for all pixels from a single viewing location. Attempts to use range cameras for metrology applications have been hampered by the multi-path problem, which causes range distortions when stray light interferes with the range measurement in a given pixel. Correcting multi-path distortions by post-processing the three-dimensional measurement data has been investigated, but enjoys limited success because the interference is highly scene dependent. An alternative approach based on separating the strongest and weaker sources of light returned to each pixel, prior to range decoding, is more successful, but has only been demonstrated on custom built range cameras, and has not been suitable for general metrology applications. In this paper we demonstrate an algorithm applied to both the Mesa Imaging SR-4000 and Canesta Inc. XZ-422 Demonstrator unmodified off-the-shelf range cameras. Additional raw images are acquired and processed using an optimization approach, rather than relying on the processing provided by the manufacturer, to determine the individual component returns in each pixel. Substantial improvements in accuracy are observed, especially in the darker regions of the scene
Forward Vehicle Collision Warning Based on Quick Camera Calibration
Forward Vehicle Collision Warning (FCW) is one of the most important
functions for autonomous vehicles. In this procedure, vehicle detection and
distance measurement are core components, requiring accurate localization and
estimation. In this paper, we propose a simple but efficient forward vehicle
collision warning framework by aggregating monocular distance measurement and
precise vehicle detection. In order to obtain forward vehicle distance, a quick
camera calibration method which only needs three physical points to calibrate
related camera parameters is utilized. As for the forward vehicle detection, a
multi-scale detection algorithm that regards the result of calibration as
distance priori is proposed to improve the precision. Intensive experiments are
conducted in our established real scene dataset and the results have
demonstrated the effectiveness of the proposed framework
The Hubble Legacy Archive NICMOS Grism Data
The Hubble Legacy Archive (HLA) aims to create calibrated science data from
the Hubble Space Telescope archive and make them accessible via user-friendly
and Virtual Observatory (VO) compatible interfaces. It is a collaboration
between the Space Telescope Science Institute (STScI), the Canadian Astronomy
Data Centre (CADC) and the Space Telescope - European Coordinating Facility
(ST-ECF). Data produced by the Hubble Space Telescope (HST) instruments with
slitless spectroscopy modes are among the most difficult to extract and
exploit. As part of the HLA project, the ST-ECF aims to provide calibrated
spectra for objects observed with these HST slitless modes. In this paper, we
present the HLA NICMOS G141 grism spectra. We describe in detail the
calibration, data reduction and spectrum extraction methods used to produce the
extracted spectra. The quality of the extracted spectra and associated direct
images is demonstrated through comparison with near-IR imaging catalogues and
existing near-IR spectroscopy. The output data products and their associated
metadata are publicly available through a web form at http://hla.stecf.org and
via VO interfaces. In total, 2470 spectra of 1923 unique targets are included
in the current release.Comment: 18 pages, 21 figures, accepted for publication in Astronomy &
Astrophysic
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