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Bundle adjustment – a modern synthesis
 Vision Algorithms: Theory and Practice, LNCS
, 2000
"... This paper is a survey of the theory and methods of photogrammetric bundle adjustment, aimed at potential implementors in the computer vision community. Bundle adjustment is the problem of refining a visual reconstruction to produce jointly optimal structure and viewing parameter estimates. Topics c ..."
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Cited by 386 (12 self)
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This paper is a survey of the theory and methods of photogrammetric bundle adjustment, aimed at potential implementors in the computer vision community. Bundle adjustment is the problem of refining a visual reconstruction to produce jointly optimal structure and viewing parameter estimates. Topics covered include: the choice of cost function and robustness; numerical optimization including sparse Newton methods, linearly convergent approximations, updating and recursive methods; gauge (datum) invariance; and quality control. The theory is developed for general robust cost functions rather than restricting attention to traditional nonlinear least squares.
Least Squares Fitting of Circles and Ellipses
 BIT
, 1994
"... Fitting circles and ellipses to given points in the plane is a problem that arises in many application areas, e.g. computer graphics [1], coordinate metrology [2], petroleum engineering [11], statistics [7]. In the past, algorithms have been given which fit circles and ellipses in some least squares ..."
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Cited by 60 (0 self)
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Fitting circles and ellipses to given points in the plane is a problem that arises in many application areas, e.g. computer graphics [1], coordinate metrology [2], petroleum engineering [11], statistics [7]. In the past, algorithms have been given which fit circles and ellipses in some least squares sense without minimizing the geometric distance to the given points [1], [6]. In this paper we present several algorithms which compute the ellipse for which the sum of the squares of the distances to the given points is minimal. These algorithms are compared with classical simple and iterative methods. Circles and ellipses may be represented algebraically i. e. by an equation of the form F (x) = 0. If a point is on the curve then its coordinates x are a zero of the function F . Alternatively, curves may be represented in parametric form, which is well suited for minimizing the sum of the squares of the distances.
Supporting Fast Search in Time Series for Movement Patterns in Multiple Scales
 Proc. 7th ACM Int. Conf. on Information and Knowledge Management
, 1998
"... An important investigation of time series involves searching for "movement" patterns, such as "going up" or "going down" or some combinations of them. Movement patterns can be in various scales: a large scale pattern may cover a long time period, while a small scale pattern usually covers a short ti ..."
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Cited by 36 (2 self)
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An important investigation of time series involves searching for "movement" patterns, such as "going up" or "going down" or some combinations of them. Movement patterns can be in various scales: a large scale pattern may cover a long time period, while a small scale pattern usually covers a short time period. This paper considers such scale requirement. More specifically, a pattern is defined as a regular expression of letters, where each letter describes a movement direction and covers a specified length of time (called pattern unit length). To find if a time series (or a part of it) matches a pattern, the time series is first partitioned into consecutive subseries of the unit length, and for each subseries, the direction of its best fitting line is taken as the movement direction of the subseries if the distance between the best fitting line and the subseries is within a specified tolerance (tolerance requirement). A direct implementation of pattern search will undoubtedly yield poor performance if the number of time series or the length of them is large. This paper introduces a precomputation and indexing method to facilitate fast evaluation of pattern queries in userspecified scales. An efficient precomputation algorithm is given to find the movement directions for all the subseries that satisfy the tolerance requirement. Bounding triangles are used to represent clusters of subseries. Relational database is then used to store these bounding triangles and relational operations are employed to facilitate the evaluation of pattern queries. The paper also reports some experiments performed on a reallife data set to show the efficiency and the scalability of the algorithms.
An Implicit Loop Method for Kinematic Calibration and Its Application to ClosedChain Mechanisms
 IEEE TRANS. ROBOTICS AND AUTOMATION
, 1995
"... A unified formulation for the calibration of both seriallink robots and robotic mechanisms having kinematic closedloops is presented and applied experimentally to two 6degree offreedom devices: the RSI 6DOF Hand Controller and the MEL "Modified Stewart Platform." The unification is based on an ..."
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Cited by 22 (7 self)
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A unified formulation for the calibration of both seriallink robots and robotic mechanisms having kinematic closedloops is presented and applied experimentally to two 6degree offreedom devices: the RSI 6DOF Hand Controller and the MEL "Modified Stewart Platform." The unification is based on an equivalence between endeffector measurements and constraints imposed by the closure of kinematic loops. Errors are allocated to the joints such that the loop equations are satisfied exactly, which eliminates the issue of equation scaling and simplifies the treatment of multiloop mechanisms. For the experiments reported here, no external measuring devices are used; instead we rely on measurements of displacements in some of the passive joints of the devices. Using a priori estimates of the statistics of the measurement errors and the parameter errors, the method estimates the parameters and their accuracy, and tests for unmodelled factors.
NONLINEAR DYNAMICAL SYSTEM IDENTIFICATION FROM UNCERTAIN AND INDIRECT MEASUREMENTS
, 2002
"... We review the problem of estimating parameters and unobserved trajectory components from noisy time series measurements of continuous nonlinear dynamical systems. It is first shown that in parameter estimation techniques that do not take the measurement errors explicitly into account, like regressio ..."
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Cited by 10 (0 self)
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We review the problem of estimating parameters and unobserved trajectory components from noisy time series measurements of continuous nonlinear dynamical systems. It is first shown that in parameter estimation techniques that do not take the measurement errors explicitly into account, like regression approaches, noisy measurements can produce inaccurate parameter estimates. Another problem is that for chaotic systems the cost functions that have to be minimized to estimate states and parameters are so complex that common optimization routines may fail. We show that the inclusion of information about the timecontinuous nature of the underlying trajectories can improve parameter estimation considerably. Two approaches, which take into account both the errorsinvariables problem and the problem of complex cost functions, are described in detail: shooting approaches and recursive estimation techniques. Both are demonstrated on numerical examples.
Improving the development process for Eukaryotic cell cycle models with a modeling support environment
 Simulation
, 2003
"... On behalf of: ..."
Parameter estimation for a mathematical model of the cell cycle in frog eggs
 Journal of Computational Biology
, 2005
"... Parameter values for a kinetic model of the nuclear replication–division cycle in frog eggs are estimated by fitting solutions of the kinetic equations (nonlinear ordinary differential equations) to a suite of experimental observations. A set of optimal parameter values is found by minimizing an obj ..."
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Cited by 5 (1 self)
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Parameter values for a kinetic model of the nuclear replication–division cycle in frog eggs are estimated by fitting solutions of the kinetic equations (nonlinear ordinary differential equations) to a suite of experimental observations. A set of optimal parameter values is found by minimizing an objective function defined as the orthogonal distance between the data and the model. The differential equations are solved by LSODAR and the objective function is minimized by ODRPACK. The optimal parameter values are close to the “guesstimates” of the modelers who first studied this problem. These tools are sufficiently general to attack more complicated problems, where guesstimation is impractical or unreliable. Key words: cyclindependent kinase, Mphase promoting factor, orthogonal distance regression, LevenbergMarquardt method. 1.
Estimating Growth and Mortality in StageStructured Populations
, 1997
"... This paper presents a practical numerical method for separating and estimating growth and mortality coefficients in stage or sizestructured populations using only observations of the relative or absolute abundance of each stage. The method involves writing a system of linear ordinary differential ..."
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Cited by 5 (2 self)
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This paper presents a practical numerical method for separating and estimating growth and mortality coefficients in stage or sizestructured populations using only observations of the relative or absolute abundance of each stage. The method involves writing a system of linear ordinary differential equations (ODE's) modelling the rate of change of abundance. The solution of the differential system can be numerically approximated using standard (e.g. sixth order RungeKuttaFelhberg) methods. An optimization problem whose solutions yield `optimal' coefficients for a given model is formulated. The ODE numerical integration technique can then be employed to furnish required function and gradient information to the optimization algorithm. Data fitting software package ORDPACK is then successfully employed to estimate optimal coefficients for the ODE population model. Simulation experiments with four and eightstage model populations illustrate that the method results in successful estimati...
The Calibration Index and the Role of Input Noise in Robot Calibration
 ROBOTICS RESEARCH: THE SEVENTH INTERNATIONAL SYMPOSIUM
, 1996
"... This paper addresses two topics in robot calibration: the formulation of a calibration index and the presence of input noise. The calibration index is introduced to succinctly capture the essence of a kinematic calibration method and allow insightful comparison between that method and other methods. ..."
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Cited by 5 (0 self)
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This paper addresses two topics in robot calibration: the formulation of a calibration index and the presence of input noise. The calibration index is introduced to succinctly capture the essence of a kinematic calibration method and allow insightful comparison between that method and other methods. Input noise, e.g., joint angle errors, is a potential source of error that is usually ignored, but is known to lead to bias errors in the estimates (Norton 1986). The two topics also will be seen to have a relationship. Many kinematic calibration methods have been proposed by now, and more are continually introduced. These methods differ in terms of whether an external metrology system is required (openloop methods) or not (closedloop methods), how many components of pose are measured and by what means, how many components of pose are passively constrained and how, whether there are unsensed joints, and whether a serial or parallel mechanism is being calibrated (Hollerbach 1993). It can be very difficult to understand how one method is related to another method, or what the tradeoffs are in selecting a calibration method. This statement is particularly true for parallel linkages, with different mixtures of sensed and unsensed joints, and passive and active joints. It is not always immediately obvious how easy a parallel linkage is to calibrate, especially by a closedloop method. The literature on camera calibration is usually distinct from that on manipulator calibration. By modeling cameras and light beams as prismatic legs, it is possible to fold camera calibration into manipulator calibration. An advantage is that mixed manipulator/camera calibration problems can be handled uniformly.
of LaborIdentification of Peer Effects with Missing Peer Data: Evidence from Project STAR
, 2011
"... Any opinions expressed here are those of the author(s) and not those of IZA. Research published in this series may include views on policy, but the institute itself takes no institutional policy positions. The Institute for the Study of Labor (IZA) in Bonn is a local and virtual international resear ..."
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Cited by 2 (0 self)
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Any opinions expressed here are those of the author(s) and not those of IZA. Research published in this series may include views on policy, but the institute itself takes no institutional policy positions. The Institute for the Study of Labor (IZA) in Bonn is a local and virtual international research center and a place of communication between science, politics and business. IZA is an independent nonprofit organization supported by Deutsche Post Foundation. The center is associated with the University of Bonn and offers a stimulating research environment through its international network, workshops and conferences, data service, project support, research visits and doctoral program. IZA engages in (i) original and internationally competitive research in all fields of labor economics, (ii) development of policy concepts, and (iii) dissemination of research results and concepts to the interested public. IZA Discussion Papers often represent preliminary work and are circulated to encourage discussion. Citation of such a paper should account for its provisional character. A revised version may be