scholarly journals SINGULARITY-FREE BUNDLE ADJUSTMENT

2020 ◽  
Vol V-2-2020 ◽  
pp. 43-48
Author(s):  
E. Garcia
Keyword(s):  
Initial Conditions ◽  
Error Function ◽  
Ground Level ◽  
Bundle Adjustment ◽  
Aerial Imagery ◽  
Adjustment Process ◽  
Reprojection Error ◽  
Motion Problem ◽  
The Cost ◽  
Orientation Structure

Abstract. The photogrammetric bundle adjustment is well-behaved in the case of structured aerial imagery looking in the nadir direction. That is less so in the case of ground-level imagery with less structure and potentially looking in any direction. Besides, the cost function based on reprojection errors of tie points is not defined everywhere and exhibits singularities which renders this bundle adjustment process sensitive to initial conditions and outliers. In order to handle difficult configurations without incurring the risks posed by the reprojection function, we propose a new error function that is equivalent to the reprojection error when this error tends to zero, and that enjoys many desirables properties, such as being defined everywhere and being continuous. This allows an easier implementation of a robust bundle adjustment, and incidentally it also allows to solve derivative problems such as triangulating points starting from arbitrary initial positions, or estimating the relative positions of calibrated and oriented cameras starting from arbitrary positions, thus offering a simple solution to the known-orientation structure-from-motion problem.

High-order relaxation approaches for adjoint-based optimal control problems governed by nonlinear hyperbolic systems of conservation laws

2016 ◽  
Vol 24 (1) ◽  
Author(s):  
Elimboto M. Yohana ◽  
Mapundi K. Banda
Keyword(s):  
Optimal Control ◽  
Conservation Laws ◽  
Optimal Control Problems ◽  
Initial Conditions ◽  
Hyperbolic Systems ◽  
Control Problems ◽  
Computational Investigation ◽  
Backward Problem ◽  
Systems Of Conservation Laws ◽  
The Cost

AbstractA computational investigation of optimal control problems which are constrained by hyperbolic systems of conservation laws is presented. The general framework is to employ the adjoint-based optimization to minimize the cost functional of matching-type between the optimal and the target solution. Extension of the numerical schemes to second-order accuracy for systems for the forward and backward problem are applied. In addition a comparative study of two relaxation approaches as solvers for hyperbolic systems is undertaken. In particular optimal control of the 1-D Riemann problem of Euler equations of gas dynamics is studied. The initial values are used as control parameters. The numerical flow obtained by optimal initial conditions matches accurately with observations.

scholarly journals A Parametric Starting Study of an Axial-Centrifugal Gas Turbine Engine Using a One-Dimensional Dynamic Engine Model and Comparisons to Experimental Results: Part 1 — Model Development and Facility Description

1998 ◽  
Author(s):  
A. Karl Owen ◽  
Anne Daugherty ◽  
Doug Garrard ◽  
Howard C. Reynolds ◽  
Richard D. Wright
Keyword(s):  
Gas Turbine ◽  
Initial Conditions ◽  
Model Development ◽  
Ground Level ◽  
Gas Turbine Engine ◽  
Calibration Data ◽  
Gas Generator ◽  
Turbine Engine ◽  
One Dimensional ◽  
Engine Model

A generic one-dimensional gas turbine engine model, developed at the Arnold Engineering Development Center, has been configured to represent the gas generator of a General Electric axial-centrifugal gas turbine engine in the six kg/sec airflow class. The model was calibrated against experimental test results for a variety of initial conditions to insure that the model accurately represented the engine over the range of test conditions of interest. These conditions included both assisted (with a starter motor) and unassisted (altitude windmill) starts. The model was then exercised to study a variety of engine configuration modifications designed to improve its starting characteristics and thus quantify potential starting improvements for the next generation of gas turbine engines. This paper discusses the model development and describes the test facilities used to obtain the calibration data. The test matrix for the ground level testing is also presented. A companion paper presents the model calibration results and the results of the trade-off study.

scholarly journals Coupling ground-level panoramas and aerial imagery for change detection

2016 ◽  
Vol 19 (3) ◽  
pp. 222-232 ◽  
Author(s):  
Nehla Ghouaiel ◽  
Sébastien Lefèvre
Keyword(s):  
Change Detection ◽  
Ground Level ◽  
Aerial Imagery

scholarly journals A method for estimating Hill function-based dynamic models of gene regulatory networks

2018 ◽  
Vol 5 (2) ◽  
pp. 171226 ◽  
Author(s):  
Faizan Ehsan Elahi ◽  
Ammar Hasan
Keyword(s):  
Gene Regulatory Networks ◽  
Regulatory Networks ◽  
Optimization Problem ◽  
Dynamic Models ◽  
Initial Conditions ◽  
Computational Cost ◽  
Optimization Approach ◽  
Continuous Models ◽  
Gene Regulatory ◽  
The Cost

Gene regulatory networks (GRNs) are quite large and complex. To better understand and analyse GRNs, mathematical models are being employed. Different types of models, such as logical, continuous and stochastic models, can be used to describe GRNs. In this paper, we present a new approach to identify continuous models, because they are more suitable for large number of genes and quantitative analysis. One of the most promising techniques for identifying continuous models of GRNs is based on Hill functions and the generalized profiling method (GPM). The advantage of this approach is low computational cost and insensitivity to initial conditions. In the GPM, a constrained nonlinear optimization problem has to be solved that is usually underdetermined. In this paper, we propose a new optimization approach in which we reformulate the optimization problem such that constraints are embedded implicitly in the cost function. Moreover, we propose to split the unknown parameter in two sets based on the structure of Hill functions. These two sets are estimated separately to resolve the issue of the underdetermined problem. As a case study, we apply the proposed technique on the SOS response in Escherichia coli and compare the results with the existing literature.

scholarly journals Nonlinear inversion method based on dynamics model modification

2019 ◽  
Vol 288 ◽  
pp. 01003
Author(s):  
Faping Zhang ◽  
Kai Wu
Keyword(s):  
Dynamic Models ◽  
Error Function ◽  
Experimental Results ◽  
Inversion Method ◽  
Nonlinear Inversion ◽  
Forward Modelling ◽  
Dynamics Model ◽  
Model Modification ◽  
Simulation Results ◽  
The Cost

In the fields of modern aviation system, subgrade vehicle system and complex mechanical system, there is a problem that parameters of most dynamic models are inaccurate. This problem results in a large difference between the model results and the experimental results. In order to solve this problem, this paper build a nonlinear inversion method based on dynamics model modification (NIDM). Firstly, the error relationship was obtained by integrating the experimental data with the simulation results of the forward modelling model by the cost function and penalty function. Then, the problem of error function minimization was solved by using the parameter iteration generated by particle swarm optimization algorithm, and the corrected parameters of the forward modelling model were obtained. Finally, the method was tested by building a vehicle suspension vibration model and a pavement excitation model as test samples. The test results show that the fitting degree between the simulation results and the experimental results can be effectively improved by modifying the parameters of the dynamic model based on the NIDM method.

Refraction-Based Bundle Adjustment for Scale Reconstructible Structure from Motion

2018 ◽  
Vol 30 (4) ◽  
pp. 660-670 ◽  
Author(s):  
Akira Shibata ◽  
Yukari Okumura ◽  
Hiromitsu Fujii ◽  
Atsushi Yamashita ◽  
Hajime Asama ◽  
...  
Keyword(s):  
3D Reconstruction ◽  
Structure From Motion ◽  
Error Function ◽  
Bundle Adjustment ◽  
Reconstruction Method ◽  
Actual Measurement ◽  
3D Measurements ◽  
Absolute Scale ◽  
The Absolute ◽  
Motion Method

Structure from motion is a three-dimensional (3D) reconstruction method that uses one camera. However, the absolute scale of objects cannot be reconstructed by the conventional structure from motion method. In our previous studies, to solve this problem by using refraction, we proposed a scale reconstructible structure from motion method. In our measurement system, a refractive plate is fixed in front of a camera and images are captured through this plate. To overcome the geometrical constraints, we derived an extended essential equation by theoretically considering the effect of refraction. By applying this formula to 3D measurements, the absolute scale of an object could be obtained. However, this method was verified only by a simulation under ideal conditions, for example, by not taking into account real phenomena such as noise or occlusion, which are necessarily caused in actual measurements. In this study, to robustly apply this method to an actual measurement with real images, we introduced a novel bundle adjustment method based on the refraction effect. This optimization technique can reduce the 3D reconstruction errors caused by measurement noise in actual scenes. In particular, we propose a new error function considering the effect of refraction. By minimizing the value of this error function, accurate 3D reconstruction results can be obtained. To evaluate the effectiveness of the proposed method, experiments using both simulations and real images were conducted. The results of the simulation show that the proposed method is theoretically accurate. The results of the experiments using real images show that the proposed method is effective for real 3D measurements.

GPS for Aviation

1983 ◽  
Vol 36 (3) ◽  
pp. 350-355
Author(s):  
S. Ratcliffe
Keyword(s):  
First Principles ◽  
Ground Level ◽  
Satellite System ◽  
Three Dimensions ◽  
Technical Knowledge ◽  
The Public ◽  
Mode Of Operation ◽  
Acquisition Mode ◽  
The Cost

It must be stated at the outset that the present author has a technical knowledge of Navstar GPS based only on fragments of the literature open to the public, and no knowledge whatever about the plans for its military use. An attempt will be made to discuss, from first principles, the consequences to both civil and friendly military users of the availability of a global, satellite-based navaid that makes possible the determination of position in three dimensions to a high accuracy. For civil users, confined to the ‘coarse acquisition’ mode, there is a 95 per cent probability that the horizontal position error will not exceed about 20 metres. For military users holding the key to a more sophisticated mode of operation, a significantly greater accuracy is available. The GPS also determines velocity, and data can be updated every second or so. It will be assumed that the navaid covers all the Earth's surface of interest, down to ground level. The cost of the satellite system is assumed to be high.

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