Thesis (M.S. in Applied Physics) Naval Postgraduate School, Dec. 2001. / Thesis advisors: D. Scott Davis, Richard Harkins. "December 2001." Includes bibliographical references (p. 65). Also available online.

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Thesis (Ph. D.)--University of Washington, 1997. / Vita. Includes bibliographical references (leaves [137]-142).

Thesis (M. Phil.)--University of Hong Kong, 1994. / Includes bibliographical references (leaves [126]-127).

Calibration is a fundamental step towards producing radio interferometric images. However, naive calibration produces calibration artefacts, in the guise of spurious emission, buried in the thermal noise. This work investigates these calibration artefacts, henceforth referred to as “ghosts”. A 21 cm observation with the Westerbork Synthesis Radio Telescope yielded similar ghost sources, and it was anticipated that they were due to calibrating with incomplete sky models. An analytical ghost distribution of a two-source scenario is derived to substantiate this theory and to seek answers to the related bewildering features (regular ghost pattern, points spread function-like sidelobes, independent of model flux). The theoretically predicted ghost distribution qualitatively matches with the observational ones and shows high dependence on the array geometry. The theory draws the conclusion that both the ghost phenomenon and suppression of the unmodelled flux have the same root cause. In addition, the suppression of the unmodelled flux is studied as functions of unmodelled flux, differential gain solution interval and the number of sources subjected to direction-dependent gains. These studies summarise that the suppression rate is constant irrespective of the degree of incompleteness of the calibration sky model. In the presence of a direction-dependent effect, the suppression drastically increases; however, this increase can be compensated for by using longer solution intervals.

The need for absolute radiometric calibration of space-based sensors will continue to increase as new generations of space sensors are developed. A reflectance-based in-flight calibration procedure is used to determine the radiance reaching the entrance pupil of the sensor. This procedure uses ground-based measurements coupled with a radiative transfer code to characterize the effects the atmosphere has on the signal reaching the sensor. The computed radiance is compared to the digital count output of the sensor associated with the image of a test site. This provides an update to the preflight calibration of the system and a check on the on-board internal calibrator. This calibration procedure was used to perform a series of five calibrations of the Landsat-5 Thematic Mapper (TM). For the 12 measurements made in TM bands 1-3, the RMS variation from the mean as a percentage of the mean is (+OR-) 1.9%, and for measurements in the IR, TM bands 4,5, and 7, the value is (+OR-) 3.4%. The RMS variation for all 23 measurements is (+OR-) 2.8%. The absolute calibration techniques were put to another test with a series of three calibration of the SPOT-1 High Resolution Visible, (HRV), sensors. The ratio, HRV-2/HRV-1, of absolute calibration coefficients compared very well with ratios of histogrammed data obtained when the cameras simultaneously imaged the same ground site. Bands PA, B1 and B3 agreed to within 3%, while band B2 showed a 7% difference. The procedure for performing a satellite calibration was then used to demonstrate how a calibrated satellite sensor can be used to quantitatively evaluate surface reflectance over a wide range of surface features. Predicted reflectance factors were compared to values obtained from aircraft-based radiometer data. This procedure was applied on four dates with two different surface conditions per date. A strong correlation, R('2) = .996, was shown between reflectance values determined from satellite imagery and low-flying aircraft data. Of the 32 predicted reflectance values only six had a difference greater than 0.01. A mean difference of .0007 was obtained for the 32 cases. In addition, a procedure had to be developed to obtain uncorrected digital counts from processed satellite imagery.

This thesis studies calibration of SIDRA Intersection roundabout models. The calibration has been performed with three different methods; manual calibration of gap-acceptance parameters, manual calibration of the parameter environment factor and automatic calibration of the environment factor based on optimization. The main aim has been to evaluate and compare 3 the three methods. One part of the purpose was also to test the possibility of finding a general value of environment factor by testing a few different types of models. SIDRA Intersection is a micro-analytical model used for capacity and performance estimations. The capacity model is based on gap-acceptance theory where follow-up headway and critical gap have a great impact. An application for automatic calibration was developed in Microsoft Excel/VBA. The calibration process is based Differential evolution and the cost function uses root mean square percent error where capacity and average delay are used as performance measures. The application has been tested with a test model at first to make sure the calibration is correct. The application has then been tested on data from a site in Farsta, Stockholm. For this site all three calibration methods, the two manual and the automatic, has been tested. The results show that all three methods performed equally well, with only small differences in precision. The most effective method considering results and time required for process was the manual calibration of environment factor.In the last part of this project the method for manual calibration of environment factor was tested with three more models with different characteristics in order to investigate the possibility of finding one value for environment factor suitable for all approaches. However the tests show difference in environment factor between small and large roundabouts and difficulties to set one value for environment factor for two-lane approaches.

No description available.

This thesis discusses the kinematic calibration of the constraining linkage of a four degrees of freedom parallel manipulator. The manipulator has hybrid actuation of joints and wires, however the wires are not considered in this calibration. Two of the passive joints of the manipulator contain sensing so the calibration of the constraining linkage can be considered. Four kinematic models are developed for the manipulator. For each of these models, an independent set of model parameters are identified through an analysis of the augmented identification Jacobian matrix. Three different methods for formulating the augmented identification Jacobian matrix are explored. For the calibration, an optical tracking system is used to track the end-effector of the manipulator. The procedure to collect the calibration data is explained and the sources of error are considered. To further analyze the sources of error, simulated input data is created and the calibration using the experimental data and the simulated data are compared. In an attempt to improve the calibration, the selection of measured poses to be used for calibration is explored. Several different pose selection criteria have been proposed in the literature and five are evaluated in this work. The pose selection criteria were applied to the experimental manipulator and also a simulated two degrees of freedom manipulator. It is found that the pose selection criteria have a large impact when few poses are used; however the best results occur when a large number of poses are used for the calibration. An experimental calibration is carried out for the manipulator. Using the joint encoders and the kinematic model, the expected pose of the end-effector is calculated. The actual pose is measured using a vision tracking system and the difference between the actual and expected pose is minimized by adjusting the model parameters using a nonlinear optimization method. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2013-01-06 22:46:05.076

The Remote Sensing Group (RSG) at the University of Arizona performs the vicarious calibration of airborne and spaceborne sensors using ground-based measurements. Vicarious calibration is important because it is independent of the sensor and any onboard calibration system, but it requires that RSG personnel be present at a test site during the aircraft or satellite overpass. The ground-based data collection can be limited by poor weather, and also by the large travel distances from RSG's laboratory to the test sites.This dissertation presents an automated methodology that is used in support of vicarious calibration. The most important parameter measured during a vicarious calibration field campaign is the surface reflectance, and this work describes the method and instrumentation to obtain surface reflectance in the absence of RSG personnel. The instrumentation required to measure the surface and atmospheric parameters is discussed. The design and laboratory characterization of a nadir-viewing, multispectral radiometer is presented. Finally, results using this methodology are compared to those obtained using vicarious calibration, and also with the top-of-atmosphere radiance for one Terra MODIS, and two Aqua MODIS overpasses.