scholarly journals Online Correction of the Mutual Miscalibration of Multimodal VIS–IR Sensors and 3D Data on a UAV Platform for Surveillance Applications

2019 ◽  
Vol 11 (21) ◽  
pp. 2469
Author(s):  
Siekański ◽  
Paśko ◽  
Malowany ◽  
Malesa
Keyword(s):  
Coordinate System ◽  
Critical Infrastructure ◽  
Spatial Coherence ◽  
Phase Correlation ◽  
Geometric Calibration ◽  
System A ◽  
3D Data ◽  
Common Coordinate System ◽  
Ir Sensors ◽  
Imaging Camera

Unmanned aerial vehicles (UAVs) are widely used to protect critical infrastructure objects, and they are most often equipped with one or more RGB cameras and, sometimes, with a thermal imaging camera as well. To obtain as much information as possible from them, they should be combined or fused. This article presents a situation in which data from RGB (visible, VIS) and thermovision (infrared, IR) cameras and 3D data have been combined in a common coordinate system. A specially designed calibration target was developed to enable the geometric calibration of IR and VIS cameras in the same coordinate system. 3D data are compatible with the VIS coordinate system when the structure from motion (SfM) algorithm is used. The main focus of this article is to provide the spatial coherence between these data in the case of relative camera movement, which usually results in a miscalibration of the system. Therefore, a new algorithm for the detection of sensor system miscalibration, based on phase correlation with automatic calibration correction in real time, is introduced.

scholarly journals Zur exakten Behandlung von kollektiven Rotationen Teil A: Theorie / On the Exact Treatment of Collective Rotations Part A: Theory

1973 ◽  
Vol 28 (2) ◽  
pp. 206-215
Author(s):  
Hanns Ruder
Keyword(s):  
Coordinate System ◽  
Perturbation Expansion ◽  
Rotational Energy ◽  
The Body ◽  
System A ◽  
N Body Problem ◽  
Definition Of ◽  
Fixed System ◽  
Body Fixed Coordinate System ◽  
Groundstate Energy

Basic in the treatment of collective rotations is the definition of a body-fixed coordinate system. A kinematical method is derived to obtain the Hamiltonian of a n-body problem for a given definition of the body-fixed system. From this exact Hamiltonian, a consequent perturbation expansion in terms of the total angular momentum leads to two exact expressions: one for the collective rotational energy which has to be added to the groundstate energy in this order of perturbation and a second one for the effective inertia tensor in the groundstate. The discussion of these results leads to two criteria how to define the best body-fixed coordinate system, namely a differential equation and a variational principle. The equivalence of both is shown.

HIGH-PRECISION IN-FLIGHT CALIBRATION USING UNKNOWN LANDMARKS

2021 ◽  
Vol 4 ◽  
pp. 117-124
Author(s):  
Alexander Tkachenko ◽  
Keyword(s):  
Good Accuracy ◽  
Star Tracker ◽  
Coordinate Frame ◽  
Geometric Calibration ◽  
The Earth ◽  
Imaging Camera ◽  
Calibration Accuracy ◽  
Combined Algorithm ◽  
Fuzzy State ◽  
Fuzzy State Observer

An in-flight geometric calibration (further — calibration) is interpreted here as a procedure of making more preceise mutual attitude parameters of the onboard imaging camera and the star tracker. The problem of calibration is solved with using of observations of the landmarks from the orbit. In this work, the landmarks are considered as unknown in the sense that they may be identified on the several snapshots, they may be associated with synchronous data of the star tracker and GPS, but their location in the Earth coordinate frame is unknown. While unknown markers are used, it is more complicated to provide high accuracy of calibration than when geo-referenced markers are observed. In such a situation, improvement of the onboard devices and gauges and increasing of their accuracy strenghtens advisability of agreement of attainable accuracy of calculations while in-flight geometric calibration with accessible measurings accuracy. It concerns properly calibration so as geo-referencing of space snaps using results of calibration. In particular, it is important to consider how accuracy of calibration depends on the accuracy of specific measurings and initial data. Actuality of the considered problem is indisputable. Without its solution, attraction of high-accurate measurings is senseless. A main means of investigation is computer simulanion and analysis of its results. The combined algorithm is proposed for the processing of the calibration measuring equations. It consists of two independent parts. The first one belongs to author of this work and is based on photogrammetric condition of collinearity The second part belongs to D.V. Lebedev and is based on photogrammetric condition of coplanarity. The method of state estimation with high convergence characteristics — fuzzy state observer — is used for resolving of measuring equations. The results of above-mentioned calibration are fully fit for the geo-referencing of the unknown ground objects with acceptable accuracy. Computer simulation had demonsrated good accuracy of the proposed method of the in-flight geometric calibration using unknown landmarks in a combination with high-precise characteristics of used technical means. The simulation had shown the calibration accuracy on the level of 5 arc sec and accuracy of the geo-referencing on the level of 10–20 m. It is fully comparable with accuracy when geo-referenced markers are observated.

Real-Time Occlusion Between Real and Digital Objects in Augmented Reality

2018 ◽  
Author(s):  
Kevin Lesniak ◽  
Conrad S. Tucker
Keyword(s):  
Augmented Reality ◽  
Coordinate System ◽  
Real Time ◽  
Real World ◽  
Virtual Object ◽  
Virtual Objects ◽  
Common Coordinate System ◽  
Realistic Representation ◽  
Lead Users

The method presented in this work reduces the frequency of virtual objects incorrectly occluding real-world objects in Augmented Reality (AR) applications. Current AR rendering methods cannot properly represent occlusion between real and virtual objects because the objects are not represented in a common coordinate system. These occlusion errors can lead users to have an incorrect perception of the environment around them when using an AR application, namely not knowing a real-world object is present due to a virtual object incorrectly occluding it and incorrect perception of depth or distance by the user due to incorrect occlusions. The authors of this paper present a method that brings both real-world and virtual objects into a common coordinate system so that distant virtual objects do not obscure nearby real-world objects in an AR application. This method captures and processes RGB-D data in real-time, allowing the method to be used in a variety of environments and scenarios. A case study shows the effectiveness and usability of the proposed method to correctly occlude real-world and virtual objects and provide a more realistic representation of the combined real and virtual environments in an AR application. The results of the case study show that the proposed method can detect at least 20 real-world objects with potential to be incorrectly occluded while processing and fixing occlusion errors at least 5 times per second.

SOLVING SPATIAL CONSTRAINTS WITH GLOBAL DISTANCE COORDINATE SYSTEM

2006 ◽  
Vol 16 (05n06) ◽  
pp. 533-547 ◽  
Author(s):  
LU YANG
Keyword(s):  
Coordinate System ◽  
Systematic Approach ◽  
Distance Geometry ◽  
Spatial Constraints ◽  
Constraint Equations ◽  
System A ◽  
Short Program ◽  
Complete Set ◽  
Point Line ◽  
Made In

A systematic approach making use of distance geometry to solve spatial constraints is introduced. We demonstrate how to create the constraint equations by means of a relevant distance coordinate system. A short program is made (in Maple) which implements the algorithm producing automatically a complete set of constraint equations for a given point-plane configuration. The point-line-plane configurations are converted into point-plane ones beforehand.

Photogrammetric Investigation of Byrd Glacier Surface Lowering (Abstract only)

1982 ◽  
Vol 3 ◽  
pp. 353 ◽  
Author(s):  
Henry H. Brecher
Keyword(s):  
Coordinate System ◽  
Fixed Points ◽  
Aerial Photography ◽  
Geological Survey ◽  
Topographic Maps ◽  
Independent Data ◽  
Glacier Surface ◽  
The Third ◽  
Common Coordinate System ◽  
Ground Survey

While carrying out photogrammetric measurements to provide surface velocities and elevations for use in studies of the equilibrium and dynamics of Byrd Glacier, I noted that comparison of elevations obtained by ground surveys in 1978-79 with US Geological Survey topographic maps made from 1960-62 aerial photography indicated a very large apparent lowering of the glacier surface in this short timeinterval. The apparent lowering varied between 50 and 150 m along a 60 km section of the glacier for which data were available (Brecher 1980). The ground measurements were estimated to be in error by no more than 3 in but the accuracy of elevations on the maps was unknown. Because these are reconnaissance maps, however, substantial errors would not be unexpected. It was therefore necessary to obtain more accurate glacier surface elevations for 1960–62 in order to determine whether the lowering is real. Photogrammetric strip triangulations of three individual strips of photography, two taken in November 1960 and the third in February 1963, which cover the region of the greatest apparent lowering, have now been completed. The old strips were oriented to fixed points on the two “banks” of the glacier derived for this purpose from the 1978–79 photogrammetric work, thus bringing the measurements from the old and new photography into a common coordinate system. The glacier surface elevations for 1960–62 are the same as those obtained from the 1978–79 ground survey and photogrammetry. While it is difficult to give measures of accuracy of the results since no independent data are available for comparison, internal evidence indicates that precision higher than the expected 10 m has been achieved in the measurements. It can thus be stated unambiguously that no detectable surface lowering has occurred on any of the parts of the glacier which have been investigated.

Validation methods for geometric camera calibration

2020 ◽  
Vol 2020 (16) ◽  
pp. 150-1-150-6
Author(s):  
Paul Romanczyk
Keyword(s):  
Coordinate System ◽  
Camera Calibration ◽  
Image Plane ◽  
Test Validation ◽  
Driver Assistance ◽  
Driver Assistance Systems ◽  
Geometric Calibration ◽  
Calibration Models ◽  
The World ◽  
Assistance Systems

Camera-based advanced driver-assistance systems (ADAS) require the mapping from image coordinates into world coordinates to be known. The process of computing that mapping is geometric calibration. This paper provides a series of tests that may be used to assess the goodness of the geometric calibration and compare model forms: 1. Image Coordinate System Test: Validation that different teams are using the same image coordinates. 2. Reprojection Test: Validation of a camera’s calibration by forward projecting targets through the model onto the image plane. 3. Projection Test: Validation of a camera’s calibration by inverse projecting points through the model out into the world. 4. Triangulation Test: Validation of a multi-camera system’s ability to locate a point in 3D. The potential configurations for these tests are driven by automotive use cases. These tests enable comparison and tuning of different calibration models for an as-built camera.

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