Precalibration Procedure Research Articles

A close-range photogrammetric model for tracking and performance-based forecasting earthmoving operations

PurposeThis paper aims to present a highly accessible and affordable tracking model for earthmoving operations in an attempt to overcome some of the limitations of current tracking models.Design/methodology/approachThe proposed methodology involves four main processes: acquiring onsite terrestrial images, processing the images into 3D scaled cloud data, extracting volumetric measurements and crew productivity estimations from multiple point clouds using Delaunay triangulation and conducting earned value/schedule analysis and forecasting the remaining scope of work based on the estimated performance. For validation, the tracking model was compared with an observation-based tracking approach for a backfilling site. It was also used for tracking a coarse base aggregate inventory for a road construction project.FindingsThe presented model has proved to be a practical and accurate tracking approach that algorithmically estimates and forecasts all performance parameters from the captured data.Originality/valueThe proposed model is unique in extracting accurate volumetric measurements directly from multiple point clouds in a developed code using Delaunay triangulation instead of extracting them from textured models in modelling software which is neither automated nor time-effective. Furthermore, the presented model uses a self-calibration approach aiming to eliminate the pre-calibration procedure required before image capturing for each camera intended to be used. Thus, any worker onsite can directly capture the required images with an easily accessible camera (e.g. handheld camera or a smartphone) and can be sent to any processing device via e-mail, cloud-based storage or any communication application (e.g. WhatsApp).

Smartphone-Based Photogrammetry Assessment in Comparison with a Compact Camera for Construction Management Applications

Close-range photogrammetry (CRP) has proven to be a remarkable and affordable technique for data modeling and measurements extraction in construction management applications. Nevertheless, it is important to aim for making CRP more accessible by using smartphones on-site directly without a pre-calibration procedure. This study evaluated the potential of smartphones as data acquisition tools in comparison with compact cameras based on the quality and accuracy of their photogrammetric results in extracting geometrical measurements (i.e., surface area and volume). Two concrete specimens of regular shapes (i.e., beam and cylinder) along with an irregular-shaped sand pile were used to conduct this study. The datasets of both cameras were analyzed and compared based on lens distortions, image residuals, and projections multiplicity. Furthermore, the photogrammetric models were compared according to various quality criteria, processing time, and memory utilization. Though both cameras were not pre-calibrated, they both provided highly accurate geometrical estimations. The volumetric estimation error ranged from 0.37% to 2.33% for the compact camera and 0.67% to 3.19% for the smartphone. For surface area estimations, the error ranged from 0.44% to 0.91% for the compact camera and 0.50% to 1.89% for the smartphone. Additionally, the smartphone data required less processing time and memory usage with higher applicability compared with the compact camera. The implication of these findings is that they provide professionals in construction management with an assessment of a more direct and cost-effective 3D data acquisition tool with a good understanding of its reliability. Moreover, the assessment methodology and comparison criteria presented in this study can assist future research in conducting similar studies for different capturing devices in construction management applications. The findings of this study are limited to small quantification applications. Therefore, it is recommended to conduct further research that assesses smartphones as a photogrammetric data acquisition tool for larger construction elements or tracking ongoing construction activities that involve measurements estimation.

Efficient method for the compensation of dispersion mismatch in the frequency-scanning interferometry

Absolute distance measurements could be achieved by the technique of frequency scanning interferometry (FSI), which could provide a micron-level accuracy over several tens of meters. However, as the scanning range and distance increasing, the measurement accuracy and resolution would be seriously influenced by the dispersion mismatch effect, which is mainly caused by the dispersion difference between optical fiber and air. A dispersion compensation method was proposed in this paper, and the mismatch effect would be suppressed effectively without complicated calculations for each single measurement. The chirp in resampling clock would be corrected with a pre-calibration procedure, and the compensation factor is demonstrated for different distances. A calibration method of dispersion compensation factor is also proposed, and the linear regression residual is employed as the criterion. Then, the compensation method is evaluated by experiments with different spatial distances and scanning ranges. Finally, a 60-m experiment is carried out for accuracy comparison, and the measurement accuracy is better than 15 µm by comparing with commercial interferometers.

Real-Time Adaptive Spectral Filter Based Parasitic Vibration Cancellation in Self-Mixing Laser Sensor Signals

Parasitic motion corrupts the measurement of all non-contact sensor systems. It thus hinders deployment of these sensors for such real-world applications where it is impossible to keep the sensor perfectly stationary. In this paper, an adaptive algorithm is presented to remove parasitic vibrations corrupting the measurements of a self-mixing (SM) interferometric laser sensor. Previously, this was achieved by coupling a solid state accelerometer (SSA) with the SM sensor followed by either a pre-calibration based design or a time-domain adaptive filter based system. The proposed method is based on adaptive spectral filtering where filter coefficients are derived based on the parasitic vibrations present in the retrieved target motion. Importantly, it neither requires any pre-calibration procedure nor has any dependence on parameters such as filter-order, convergence criteria, or step-size (required in case of time-domain adaptive filters), thus making the proposed scheme a suitable choice for mass production of SSA-SM sensor systems. The proposed algorithm provides improved mean RMS error of 5.37 nm as opposed to 19.1 nm for least mean square (LMS) filter, 20.22 nm for recursive least square (RLS) filter, and 24.7 nm for pre-calibration based system. This method’s performance has also been characterized and an embedded, real-time, hardware design is also presented. At the end, hardware system results (on experimental data-set) and sensor bounds/bandwidth are also quantified.

Mid-infrared radiation technique for direct pyroelectric and electrocaloric measurements.

A mid-infrared radiometric (MIR) method for precise in situ temperature measurements when studying pyroelectric and electrocaloric properties of bulk and film materials is presented. The method uses new MIR-temperature sensors based on narrowband high-speed and high-sensitive uncooled immersion lens A3B5 photodiodes with a precalibration procedure. They are completely insensitive to the background illumination with λ ≤ 1 µm and provide contactless temperature measurements directly in the area of laser heating action. An accuracy of 50 mK at the temperature around 20 °C, rapidly improving up to 1 mK at 200 °C, is achieved at the operation speed of 1 ms. The reliable and reproducible conditions of measurements of pyroelectric and electrocaloric properties of various samples are formulated, and the novel experimental setup is described in detail. The experimental verification of the method is performed by the measurements of pyroelectric properties of single crystals, bulk ceramics, and AlN film. The results of joint measurements of the pyroelectric and electrocaloric properties of the ferroelectric relaxor ceramics are also presented.

Calibration of methylene-referenced lipid-dissolved xenon frequency for absolute MR temperature measurements.

Absolute MR temperature measurements are currently difficult because they require precalibration procedures specific for tissue types and conditions. Reference of the lipid-dissolved 129 Xe resonance frequency to temperature-insensitive methylene protons (rLDX) has been proposed to remove the effect of macro- and microscopic susceptibility gradients to obtain absolute temperature information. The scope of this work is to evaluate the rLDX chemical shift (CS) dependence on lipid composition to estimate the precision of absolute temperature measurements in lipids. Neat triglycerides, vegetable oils, and samples of freshly excised human and rodent adipose tissue (AT) are prepared under 129 Xe atmosphere and studied using high-resolution NMR. The rLDX CS is measured as a function of temperature. 1 H spectra are also acquired and the consistency of methylene-referenced water proton and rLDX CS values are compared in human AT. Although rLDX CS shows a dependence on lipid composition, in human and rodent AT samples the rLDX shows consistent CS values with a similar temperature dependence (-0.2058±0.0010) ppm/°C × T (°C) + (200.15±0.03) ppm, enabling absolute temperature measurements with an accuracy of 0.3°C. Methylene-referenced water CS values present variations of up to 4°C, even under well-controlled conditions. The rLDX can be used to obtain accurate absolute temperature measurements in AT, opening new opportunities for hyperpolarized 129 Xe MR to measure tissue absolute temperature.

On-Line Initialization and Extrinsic Calibration of an Inertial Navigation System With a Relative Preintegration Method on Manifold

Inertial measurement units (IMUs) are successfully utilized to compensate localization errors in sensor fused inertial navigation systems. An IMU generally produces high-frequency signals ranging from 100 to 1000 Hz, and preintegration methods are applied to effectively process these high-frequency signals for inertial navigation systems. The main problem with an existing preintegration method is that the inertial propagation models in the method are only generated at the IMU’s coordinate system. Hence, the models have to be converted to the coordinate system of the other sensor in order to apply its constraint. So, the iterative optimization framework using the conventional method takes large amount of time. In addition, since a general rigid body transformation cannot transfer a velocity propagation model to the other coordinate system, the concept of relative motion analysis needs to be considered. To solve the problems above, in this paper, we propose a novel relative preintegration (RP) method that can generate inertial propagation models at any sensor’s coordinate system in a rigid body. This permits accurate and fast IMU processing in sensor fused inertial navigation systems. We applied new nonlinear optimization frameworks to solve initialization and extrinsic calibration problems for the IMU–IMU, IMU–Camera, and IMU–LiDAR pair based on the proposed RP method in an on-line manner, and the superior results of the mentioned processes are presented as well. Note to Practitioners —In the proposed method, extrinsic calibration parameters can be estimated during the localization process without any initial manual precalibration procedure. Besides, an IMU is small and inexpensive, so small AGVs in warehouses, or mobile manipulators in factories are good applications for the proposed method, where they require a certain level of localization accuracy. The localization module using the proposed method can be mounted anywhere in a robot without restrictions. The initialization procedure has been executed for a few seconds with arbitrary movement in the field of view of the first frame, then the initial gravity and velocity vector, and extrinsic parameters, which are estimated during the initialization phase, are applied to a general SLAM problem.

Comparison of three optical tracking systems in a complex navigation scenario

Three-dimensional rotational X-ray imaging with the SIREMOBIL Iso-C3D (Siemens AG, Medical Solutions, Erlangen, Germany) has become a well-established intra-operative imaging modality. In combination with a tracking system, the Iso-C3D provides inherently registered image volumes ready for direct navigation. This is achieved by means of a pre-calibration procedure. The aim of this study was to investigate the influence of the tracking system used on the overall navigation accuracy of direct Iso-C3D navigation.Three models of tracking system were used in the study: Two Optotrak 3020s, a Polaris P4 and a Polaris Spectra system, with both Polaris systems being in the passive operation mode. The evaluation was carried out at two different sites using two Iso-C3D devices. To measure the navigation accuracy, a number of phantom experiments were conducted using an acrylic phantom equipped with titanium spheres. After scanning, a special pointer was used to pinpoint these markers. The difference between the digitized and navigated positions served as the accuracy measure.Up to 20 phantom scans were performed for each tracking system. The average accuracy measured was 0.86 mm and 0.96 mm for the two Optotrak 3020 systems, 1.15 mm for the Polaris P4, and 1.04 mm for the Polaris Spectra system. For the Polaris systems a higher maximal error was found, but all three systems yielded similar minimal errors.On average, all tracking systems used in this study could deliver similar navigation accuracy. The passive Polaris system showed – as expected – higher maximal errors; however, depending on the application constraints, this might be negligible.

Online measurement of particle size distribution during crystallization using ultrasonic spectroscopy

Particle growth during crystallization of paracetamol was monitored on-line using a new modified method based on ultrasonic spectroscopy. The model was earlier developed and tested with inert particles systems and accounts for low angle scattering and probe geometry. A graphic user interface was developed and integrated with the model based deconvolution algorithm for real-time data acquisition, analysis and display of results. The crystal growth and changes in size distribution were measured during the crystallization of paracetamol from paracetamol–isopropanol–water solution. A simplified pre-calibration procedure using acoustic velocity to estimate solution properties was established. The model based particle size distribution showed good agreement with offline measurements using laser diffraction analysis of a sample retrieved from the crystallizer.

Calibration of the CMS electromagnetic calorimeter at the LHC start up

The electromagnetic calorimeter of the CMS experiment is designed to reach excellent energy resolution, essential for the Higgs search in the H → γ γ decay channel. The non-uniformity of the individual channel responses directly contributes to the energy resolution. The target precision of the detector calibration, both of the relative response of the channels (inter-calibration) and of the electron and photon energy scale, at the 0.5% level, will be reached employing the collision events collected at the LHC. One-quarter of the barrel ECAL has been calibrated at this level of precision on electron beams. The entire barrel was calibrated with cosmic rays before installation in CMS with an accuracy at the 2% level, giving acceptable performance at the startup. During the commissioning phase in CMS about 600 million muon events have been recorded allowing to verify that the working conditions used during the pre-calibration were reproduced in CMS. The different phases of the pre-calibration procedures are summarized and the techniques for the calibration with the first LHC data are presented.

Novel lambda FRET spectral confocal microscopy imaging method

We report a highly specific, sensitive, and robust method for analyzing fluorescence resonance energy transfer (FRET) based on spectral laser scanning confocal microscopy imaging. The lambda FRET (lambdaFRET) algorithm comprises imaging of a FRET sample at multiple emission wavelengths rendering a FRET spectrum, which is separated into its donor and acceptor components to obtain a pixel-based calculation of FRET efficiency. The method uses a novel off-line precalibration procedure for spectral bleed-through correction based on the acquisition of reference reflection images, which simplifies the method and reduces variability. LambdaFRET method was validated using structurally characterized FRET standards with variable linker lengths and stoichiometries designed for this purpose. LambdaFRET performed better than other well-established methods, such as acceptor photobleaching and sensitized emission-based methods, in terms of specificity, reproducibility, and sensitivity to distance variations. Moreover, lambdaFRET analysis was unaffected by high fluorochrome spectral overlap and cellular autofluorescence. The lambdaFRET method demonstrated outstanding performance in intra- and intermolecular FRET analysis in both fixed and live cell imaging studies.

Precalibration Evaluation Procedures for Mid-Infrared Milk Analyzers

The purpose of this paper is to present a detailed account of the precalibration procedures developed and implemented by the USDA Federal Milk Market Administrators (FMMA) for evaluating mid-infrared (MIR) milk analyzers. Mid-infrared analyzers specifically designed for milk testing provide a rapid and cost-effective means for determining milk composition for payment and dairy herd improvement programs. These instruments determine the fat, protein, and lactose content of milk, and enable the calculation of total solids, solids-not-fat, and other solids. All MIR analyzers are secondary testing instruments that require calibration by chemical reference methods. Precalibration is the process of assuring that the instrument is in good working order (mechanically and electrically) and that the readings before calibration are stable and optimized. The main components of precalibration are evaluation of flow system integrity, homogenization efficiency, water repeatability, zero shift, linearity, primary slope, milk repeatability, purging efficiency, and establishment of intercorrection factors. These are described in detail and apply to both filter-based and Fourier transform infrared instruments operating using classical primary and reference wavelengths. Under the USDA FMMA Precalibration Evaluation Program, the precalibration procedures were applied longitudinally over time using a wide variety of instruments and instrument models. Instruments in this program were maintained to pass the criteria for all precalibration procedures. All instruments used similar primary wavelengths to measure fat, protein, and lactose but there were differences in reference wavelength selection. Intercorrection factors were consistent over time within all instruments and similar among groups of instruments using similar primary and reference wavelengths. However, the magnitude and sign of the intercorrection factors were significantly affected by the choice of reference wavelengths.

Automatic compensation of polarization-mode dispersion for 40 Gb/s transmission systems

We present an automatic compensator that effectively mitigates signal distortion due to polarization-mode dispersion (PMD). Accurate compensation is achieved by utilizing a degree of polarization (DOP) monitor with a measurement uncertainty of better than 1% achieved by applying a self-dependent precalibration procedure. The compensation performance at 43 Gb/s was evaluated systematically with respect to both first- and second-order PMD by using a crystal-optical PMD emulator. The compensator extended the tolerable differential group-delay (DGD) limit from 8 to 28 ps, while maintaining the Q penalty below 1 dB. In terms of the average of a Maxwellian-distributed DGD, the PMD compensator enabled transmission for up to 8 ps, or about three times higher than the level tolerated in the uncompensated case. In addition to the compensation performance, we demonstrate successful operation, even for distorted signals with high chromatic dispersion. We believe this capability will be a key enabler for a combined operation with adaptive chromatic dispersion compensators.

Fluoroscopy as an imaging means for computer-assisted surgical navigation.

Intraoperative fluoroscopy is a valuable tool for visualizing underlying bone and surgical tool positions in orthopedic procedures. Disadvantages of this technology include the need for continued radiation exposure for visual control, and cumbersome means of alignment. The purpose of this article was to highlight a new concept for a computer-assisted freehand navigation system that uses single intraoperatively acquired fluoroscopic images as a basis for real-time navigation of surgical tools. Optoelectronic markers are placed on surgical tools, a patient reference, and the fluoroscope to track their position in space. Projection properties of the fluoroscope are acquired through an initial precalibration procedure using a tracked radiopaque phantom grid. Corrections are applied to compensate for both the fluoroscope's image intensifier distortions and the mechanical bending of the C-arm frame. This enables real-time simulation of surgical tool positions simultaneously in several single-shot fluoroscopic images. In addition, through optoelectronically tracked digitization of a target viewpoint, the fluoroscope can be numerically aligned at precise angles relative to the patient without any X-ray exposure. This article shows the feasibility of this technology through its use in cadaver trials to perform the difficult task of distal locking of femoral nails.

Fluoroscopy as an Imaging Means for Computer-Assisted Surgical Navigation

Objective: Intraoperative fluoroscopy is a valuable tool for visualizing underlying bone and surgical tool positions in orthopedic procedures. Disadvantages of this technology include the need for continued radiation exposure for visual control, and cumbersome means of alignment. The purpose of this article was to highlight a new concept for a computer-assisted freehand navigation system that uses single intraoperatively acquired fluoroscopic images as a basis for real-time navigation of surgical toolsMaterials and Methods: Optoelectronic markers are placed on surgical tools, a patient reference, and the fluoroscope to track their position in space. Projection properties of the fluoro-scope are acquired through an initial precalibration procedure using a tracked radiopaque phantom grid. Corrections are applied to compensate for both the fluoroscope's image intensifier distortions and the mechanical bending of the C-arm frame. This enables real-time simulation of surgical tool positions simultaneously in several single-shot fluoroscopic images. In addition, through optoelec-tronically tracked digitization of a target viewpoint, the fluoroscope can be numerically aligned at precise angles relative to the patient without any X-ray exposureResults: This article shows the feasibility of this technology through its use in cadaver trials to perform the difficult task of distal locking of femoral nails.

Novel method for accurate g measurements in electron-spin resonance

In high-accuracy work, electron-spin-resonance (ESR) g values are generally determined by calibrating against the accurately known proton nuclear magnetic resonance (NMR). For that method—based on leakage of microwave energy out of the ESR cavity—a convenient technique is presented to obtain accurate g values without needing conscientious precalibration procedures or cumbersome constructions. As main advantages, the method allows the easy monitoring of the positioning of the ESR and NMR samples while they are mounted as close as physically realizable at all time during their simultaneous resonances. Relative accuracies on g of ≊2×10−6 are easily achieved for ESR signals of peak-to-peak width ΔBpp≲0.3 G. The method has been applied to calibrate the g value of conduction electrons of small Li particles embedded in LiF—a frequently used g marker—resulting in gLiF:Li=2.002 293±0.000 002.

Sound field audiometry: recommended stimuli and procedures.

Comprehensive recommendations are presented for conducting sound field audiometry with frequency specific stimuli. These recommendations are primarily based on a series of investigations by the authors. The rationale for each recommendation is presented, together with a brief overview of the supporting research. The preferred stimuli are frequency modulation tones, triangularly or sinusoidally modulated at a rate of about 20 Hz, or suitably generated narrow bands of noise. The optimal bandwidths of the stimuli, expressed in percentages of the center frequency, vary with frequency. Stimuli suitable for most purposes have bandwidths ranging from about 30% at 0.25 kHz to about 10% at 4 kHz. Stimuli having narrower or broader bandwidths are desirable for some special purposes. The test room should be as nonreverberant as possible and the subject should be seated on an adjustable height chair with headrest. The control microphone method of calibration is preferred but a method is also presented for carrying out the traditional precalibration procedure. The SPL of the complex stimulus should be taken as the peak deflections on a sound level meter set to "RMS-FAST." A conversion table is presented which allows thresholds obtained in the sound field to be expressed as dB HTL. With the materials and methods described here it is possible to achieve the same reliability for sound field testing as for audiometry under earphones.

A Method for Precalibrating Re-oxygenation Rates in Experimental Containers

Abstract A precalibration procedure is outlined that ensures sufficient re-oxygenation to balance oxygen demand in static containers used to hold small aquatic animals for experiment or observation. The procedure is based on predicting the rate of controlled turbulence at which re-oxygenation balances oxygen consumption at some acceptable oxygen concentration below saturation.