Correction For Refraction Research Articles

Дослідження високоточного двостороннього геометричного нівелювання

The aim of this article is to investigate the accuracy of dual line leveling, and develop a methodology for its execution to enhance the precision of elevation determination by accounting for vertical refraction and controlling the non-horizontality of the leveling beam. Methodology. Considering that digital levels can measure distances to the rod and account for the non-horizontality of the beam and vertical refraction during measurements, we propose a method of dual line leveling. The study describes the methodology for performing dual-line trigonometric leveling using the "forward-backward" method. It takes into account vertical refraction along the observation lines. Results. To test the methods for high precision class leveling applying the Holeski method (from the middle) and dual-line leveling ("forward-backward"), we selected a section with a prolonged ascent approximately 1 km in length, consisting of 5 sections. The method was tested using a Trimble DiNi-03 electronic level over two leveling lines. The discrepancies between the elevations obtained from the sections using the "from the middle" and "forward-backward" methods meet the requirements for high precision class leveling. The maximum discrepancy in the sections between the leveling methods was 0.42 mm. And it was 0.06 mm for the entire leveling route, 1,142 meters long. Originality. The paper considers the theoretical justification and experimental studies on the possibility of applying dual line leveling for high precision class observation programs and introducing a correction for vertical refraction on prolonged slopes. It is confirmed that the method of dual line leveling using the "forward-backward" method can be used for high precision class leveling by the "from the middle" method on prolonged slopes and has several advantages over it.

AN OPEN-SOURCE, DATA-LOGGING DEVICE FOR MARINE-BASED SURVEYS

Abstract. Observation, monitoring, and understanding of the marine environment, particularly seafloor mapping, have gained global attention. Underwater photogrammetry is a valuable technique for creating accurate seafloor orthomosaics and digital elevation models (DEMs). However, achieving accurate georeferencing in photogrammetry surveys is challenging in marine environments. To address this, a low-cost and open-source data collection device was developed for underwater photogrammetry projects. The device is affordable, flexible, lightweight, and capable of logging position, motion, and utilizing a laser for seafloor feature identification. This paper presents the validation and assessment of the system, focusing on the performance of the position and laser sensors. The study advances underwater photogrammetry and provides insights into the device's capabilities for marine research and mapping applications. The results show that the Post Processed Kinematic (PPK) technique achieves high accuracy, with RMSE values of 0.294 m (distance), 0.267 m (X-coordinate), and 0.12 3m (Y-coordinate) at the Fremantle car park and 0.278 m (distance), 0.16 8m (X-coordinate), and 0.222m (Y-coordinate) at the Fremantle near boat ramp. PPP exhibits acceptable accuracy, while GPS shows relatively lower accuracy. Echosounder measurements correlate well with bathymetric lidar and RTK Rover reference data, with RMSE values of 45 cm and 28 cm, respectively. The laser distance measurer provides accurate measurements between 25 and 60 cm, showing a good correlation with the echosounder (R = 0.77). After correction for offset and refraction, the laser measurements have an RMSE of 1.8 cm compared to the echosounder. This study further demonstrated the feasibility and effectiveness of low-cost and open-source platforms, like Raspberry Pi, for marine research and mapping applications. Further work will investigate integrating this data into photogrammetry surveys.

Evaluating Visual Acuity in the American Academy of Ophthalmology IRIS® Registry

To describe visual acuity data representation in the American Academy of Ophthalmology Intelligent Research in Sight (IRIS) Registry and present a data-cleaning strategy. Reliability and validity study. Patients with visual acuity records from 2018 in the IRIS Registry. Visual acuity measurements and metadata were identified and characterized from 2018 IRIS Registry records. Metadata, including laterality, assessment method (distance, near, and unspecified), correction (corrected, uncorrected, and unspecified), and flags for refraction or pinhole assessment were compared between Rome (frozen April 20, 2020) and Chicago (frozen December 24, 2021) versions. We developed a data-cleaning strategy to infer patients' corrected distance visual acuity in their better-seeing eye. Visual acuity data characteristics in the IRIS Registry. The IRIS Registry Chicago data set contains 168 920 049 visual acuity records among 23 001 531 unique patients and 49 968 974 unique patient visit dates in 2018. Visual acuity records were associated with refraction in 5.3% of cases, and with pinhole in 11.0%. Mean (standard deviation) of all measurements was 0.26 (0.41) logarithm of the minimum angle of resolution (logMAR), with a range of- 0.3 to 4.0 A plurality of visual acuity records were labeled corrected (corrected visual acuity [CVA], 39.1%), followed by unspecified (37.6%) and uncorrected (uncorrected visual acuity [UCVA], 23.4%). Corrected visual acuity measurements were paradoxically worse than same day UCVA 15% of the time. In aggregate, mean and median values were similar for CVA and unspecified visual acuity. Most visual acuity measurements were at distance (59.8%, vs. 32.1% unspecified and 8.2% near). Rome contained more duplicate visual acuity records than Chicago (10.8% vs. 1.4%). Near visual acuity was classified with Jaeger notation and (in Chicago only) also assigned logMAR values by Verana Health. LogMAR values for hand motion and light perception visual acuity were lower in Chicago than in Rome. The impact of data entry errors or outliers on analyses may be reduced by filtering and averaging visual acuity per eye over time. The IRIS Registry includes similar visual acuity metadata in Rome and Chicago. Although fewer duplicate records were found in Chicago, both versions include duplicate and atypical measurements (i.e., CVA worse than UCVA on the same day). Analyses may benefit from using algorithms to filter outliers and average visual acuity measurements over time. Proprietary or commercial disclosure may be found found in the Footnotes and Disclosures at the end of this article.

A correction for higher-order refraction in cathodoluminescence spectrometry

Cathodoluminescence (CL) is a developing analytical method in electron microscopy, because of its excellent energy resolution. Usually a Czerny–Turner type spectrometer is employed, having a blazed grating as analyzer. Unlike a prism analyzer, where the dispersion depends on the refractive index of the prism itself leading to a non-linear spectral distribution, the grating has the advantage that the spectral distribution depends linearly on the wavelength. As a draw-back, higher-order refraction alters the measured optical spectrum at larger wavelengths. In general, blazed gratings are used in order to minimize this effect in a certain spectral range. Nevertheless, the higher-order intensities can be still significant. In the present study we present a method for correcting the acquired optical spectra with respect to higher order diffraction intensities and apply it to CaO and GaN CL-spectra.

Wearable telescopic contact lens.

We describe the design, fabrication, and testing of a 1.6mm thick scleral contact lens providing both 1× and 2.8× magnified vision paths, intended for use as a switchable eye-borne telescopic low-vision aid. The F/9.7 telescopic vision path uses an 8.2mm diameter annular entrance pupil and 4 internal reflections in a polymethyl methacrylate precision optic. This gas-impermeable insert is contained inside a smooth outer casing of rigid gas-permeable polymer, which also provides achromatic correction for refraction at the curved lens face. The unmagnified F/4.1 vision path is through the central aperture of the lens, with additional transmission between the annular telescope rings to enable peripheral vision. We discuss potential solutions for providing oxygenation for an extended wear version of the lens. The prototype lenses were characterized using a scale-model human eye, and telescope functionality was confirmed in a small-scale clinical (nondispensed) demonstration.

Through‐water terrestrial laser scanning of gravel beds at the patch scale

ABSTRACTAcquiring high resolution topographic data of natural gravel surfaces is technically demanding in locations where the bed is not exposed at low water stages. Often the most geomorphologically active surfaces are permanently submerged. Gravel beds are spatially variable and measurement of their detailed structure and particle sizes is essential for understanding the interaction of bed roughness with near‐bed flow hydraulics, sediment entrainment, transport and deposition processes, as well as providing insights into the ecological responses to these processes. This paper presents patch‐scale laboratory and field experiments to demonstrate that through‐water terrestrial laser scanning (TLS) has the potential to provide high resolution digital elevation models of submerged gravel beds with enough detail to depict individual grains and small‐scale forms. The resulting point cloud data requires correction for refraction before registration. Preliminary validation shows that patch‐scale TLS through 200 mm of water introduces a mean error of less than 5 mm under ideal conditions. Point precision is not adversely affected by the water column. The resulting DEMs can be embedded seamlessly within larger sub‐aerial reach‐scale surveys and can be acquired alongside flow measurements to examine the effects of three‐dimensional surface geometry on turbulent flow fields and their interaction with instream ecology dynamics. Copyright © 2011 John Wiley & Sons, Ltd.

Novel optical system for in vitro quantification of full surface strain fields in small arteries: II. Correction for refraction and illustrative results

In a companion paper, we described a theoretical foundation for and initial experimental implementation of a novel stereo-digital image correlation (DIC) method for quantifying the size, shape and deformation of small cylindrical specimens along their full length and around their entire circumference. In this paper, we further show that this panoramic-DIC method can be used to study mouse carotid arteries without affecting their native mechanical properties and show the advantage of the approach in studying more complex mouse aorta. In particular, we first resolve the ubiquitous issue of refraction in non-contacting optical measurements of strain while tissues are immersed in physiologic saline and we show that surface preparation for DIC does not affect the inferred mechanical properties either qualitatively or quantitatively, the latter via the use of a four-fibre family hyperelastic constitutive relation and associated estimation of material parameters using nonlinear regression. We thus submit that panoramic-DIC-based strain measurement has significant potential to increase our understanding of arterial mechanics in genetic models of arterial health and disease by allowing investigators to exploit advances in transgenic mice.

Heritability of optic disc diameters: a twin study

To assess the relative influence of genetic and environmental factors on optic disc size and cup/disc ratio in healthy eyes. A sample of 55 monozygotic and 50 dizygotic healthy twin pairs aged 20-46, all having the same sex within pairs (47 pairs were male) had optic discs measured from colour fundus photographs according to the Wisconsin Protocol. Structural equation modelling was used to estimate the relative contribution of genetic and environmental factors to the phenotype. Disc dimensions did not vary significantly by age or sex. After adjusting for age and sex, additive genetic factors (i.e. heritability) explained 77% (95% CI: 65-85%) of variation of vertical disc diameters, whereas estimated unshared environmental effect was 23% (95% CI: 15-35%). For vertical cup diameters, heritability accounted for 70% (95% CI: 55-80%) and environmental factors 30% (95% CI: 20-45%). For cup/disc ratio, additive genetic and unshared environmental factors explained 66% (95% CI: 48-77%) and 34% (95% CI: 23-52%) of the variations, respectively. In this healthy twin sample, we found that three quarters of the variations in vertical optic disc and optic cup diameters were attributable to genetic influence.

Flavour-dependent radiative correction to neutrino-neutrino refraction

In the framework of the Standard Model we calculate the flavour non-universal correction for neutrino refraction in a neutrino background and verify a similar previous result for the case of ordinary-matter background. The dominant term arises at loop level and involves τ leptons circulating in the loop. These (GFmτ2) corrections to the tree-level potential provide the dominant refractive difference between νμ and ντ unless the medium contains μ or τ leptons. Our results affect the flavour evolution of dense neutrino gases and may be of interest for collective three-flavour oscillations of supernova neutrinos. We spell out explicitly how these non-universal neutrino-neutrino interactions enter the flavour oscillation equations.

Does refractive error influence the association of blood pressure and retinal vessel diameters? the blue mountains eye study

PurposeTo determine if refractive errors influence the association of blood pressure and retinal vessel diameters. DesignPopulation-based, cross-sectional study. MethodsRetinal photographs from the right eyes of participants (n = 3,654, aged 49+ years) in the Blue Mountains Eye Study taken during baseline examinations (1992 to 1994) were digitized. The diameter of all retinal vessels located half to one disk diameter from the disk margin was measured using a computer-assisted imaging program. These measurements were combined to provide the average diameters of retinal arterioles and venules of that eye, and the ratio of their diameters, the arteriole-to-venule ratio (AVR). The association of blood pressure and retinal vessel diameters was analyzed before and after correction for refraction using the Bengtsson formula. ResultsBefore correction, each 10-mm Hg increase in mean arterial blood pressure was associated with a 3.7-μm (95% confidence interval [CI], 3.2–4.3) decrease in arteriolar diameter and a 0.9-μm (95% CI, 0.3–0.9) decrease in venular diameter. After correction for refraction, each 1-mm Hg increase in mean arterial blood pressure was associated with a 3.7-μm (95% CI, 3.2–4.2) decrease in arteriolar diameter and a 0.8-μm (95% CI, 0.3–0.9) decrease in venular diameter. Refraction was not associated with the AVR and had no effect on the association of blood pressure and AVR. ConclusionRefraction had no appreciable effect on the association of blood pressure and retinal vessel diameters or on the AVR. Correction for refraction is important for quantifying absolute retinal vessel caliber, but may not be particularly important in epidemiologic studies investigating the association of generalized retinal arteriolar narrowing and hypertension.

Treatment of grazing-incidence small-angle X-ray scattering data taken above the critical angle

The equations taking into account refraction at the sample surface in grazing-incidence small-angle X-ray scattering (GISAXS) when the angle between the incoming beam and the sample surface is slightly larger than the critical angle are derived and discussed. It is demonstrated that the refraction of both the incoming and the scattered beam at the sample surface affects the GISAXS pattern and that, when a planar bidimensional detector perpendicular to the incoming beam is used, the effect depends on the azimuthal detector angle. The smearing of the pattern depending on the size of the illuminated sample area in grazing incidence is estimated by simulations with Cauchy functions of different widths. The possibility of integrating the recorded intensities over a suitable azimuthal angular range and then of making the correction for refraction is also analysed, employing simulations involving the intensity function of monodisperse interacting hard spheres. As a case study, the refraction correction is applied to the investigation of a Cu–Ni implant on silica glass.

Prey catching in the archer fish: does the fish use a learned correction for refraction?

An answer to the question of how the archer fish hits an aerial insect, despite the refraction of light at the surface of the water has not yet been found. The aims of the present studies are to find out: (1) whether the fish applies a learned correction with the virtual image as a point of reference; (2) whether deprivation of practice in squirting affects performance. For the first aim the accuracy of squirts was measured in 30 subjects. Contrary to suggestions from the literature, elevation failures were prominent but the frequencies of over- and under-squirting did not differ, which does not support the idea that the fishes applied a learned correction for refraction by using feedback from the efficacy of squirts. For the second aim, five experimental subjects were deprived of practice, whereas six control subjects got daily practice, during 6 months. The only significant difference, found thereafter, was that during the first session experimental subjects aimed more often before squirting than control subjects did, but hitting was not affected. A number of subjects developed abnormal mandibles which inevitably led to squirting too high. Our findings do not support the hypothesis that the archer fish uses learned corrections for refraction.

Refraction by Earth’s Atmosphere near 12 Microns

ABSTRACTWe have measured chromatic differential refraction of astronomical images by the Earth’s atmosphere, comparing visible light at 500–600 nm with infrared near 12 μm, and found the index of refraction near 12 μm to be greater than predicted by the dispersion relation in common use. The differential refraction between visible and 12 μm thus is smaller than the extrapolated difference. At Mauna Kea, the empirical differential refraction at 45° from zenith was measured at 0.″ 28 ± 0.″28 (3 σ) on one occasion, compared to an expected differential refraction of 0.″63–0.″69. Refractivity scales linearly with barometric pressure, and thus the inaccuracy is more severe at lower altitude observatories. The pointing error from inaccurate correction for differential refraction is comparable to the point spread function width of an 8–10 m telescope in this wavelength range. Even on smaller telescopes, accurate correction for differential refraction is necessary to guide small‐aperture spectrophotometry or to register mid‐infrared imaging with visible‐light structures.

Correction for refraction in radio astronomy and satellite geodesy

Correction for refraction in radio astronomy and satellite geodesy

Heat flow data from the western margin of the West African craton (Mauritania)

Abstract Eighteen new heat flow determinations in shallow boreholes (100–230 m) at three sites in West Africa (Mauritania) are presented. The first site is located in the Archaean province (Reguibat shield) of the West African craton. Temperature measurements were performed in iron formation and needed correction for refraction. The average value is 50 mW m−2 and radioactive element distribution in surface rocks provides an upper crust heat contribution of 1.8 μW m−3. The second site, located near the craton margin, and the third site, located in the Senegal coastal basin, display a slightly higher value of 59 mW m−2.

Perturbation correction for refraction in interferometric tomography

Perturbation correction for refraction in interferometric tomography

Saugus‐Palmdale, California, field test for refraction error in historical leveling surveys

A field test designed to measure atmospheric refraction error in historical and modern leveling was conducted in May–June 1981 on a 50‐km‐long grade from Saugus to Palmdale, California. During 1955–1971, the length of sights made between the level instrument and rods systematically decreased from 60 m to 26 m. The difference in height near Palmdale measured by single‐run long‐sight (42‐m) and short‐sight (22‐m) leveling during the test was 6 times larger than expected random error. Correction for refraction by using either the observed or modeled vertical temperature gradient in Kükkamaki's balanced sight equation reduced the height difference to the level of random error uncertainty. The observed temperature gradient obeyed a power law relation, T = a + bzc, where z is the height and a, b, and c are constants that depended on atmospheric conditions and the ground surface beneath the line of sight. The refraction‐corrected leveling satisfies the specifications and meets all standards of first‐order control surveys. The six historical surveys of the Saugus‐Palmdale grade were corrected for refraction error using the results of the experiment and for rod scale errors and nontectonic subsidence considered in previous investigations. The corrected uplift near Palmdale reached 56 ± 16 mm with respect to Saugus during the period 1955–1965. This amount of uplift is about one third that obtained before removal of refraction error. The corrected displacement profiles also reveal previously unrecognized deformation in the epicentral region of the 1971 San Fernando ML = 6.4 earthquake during the decade before the main shock.

Meteorological correction of optical beam refraction

A theoretical algorithm is presented for correction of the regular component of atmospheric refraction for various types of hydrostatic stability of the atmospheric layer adjacent to the earth. Dispersion of the random component is also calculated for various models of the atmosphere. The algorithm obtained is compared to regression equations obtained by processing an experimental data base. It is shown that within admissible accuracy limits the refraction correction algorithm obtained herein permits construction of correction tables and design of optical systems with programmable correction for atmospheric refraction on the basis of rapid meteorological measurements.

Correcting Low-Frequency Solar Radio Source Positions for Ionospheric Refraction

We describe a method for reducing displacements in radio source positions caused by ionospheric refraction. Our method is an improvement on that used by Wild et al. (1959), who assumed all frequencies in the 40-70 MHz band came from the same position above the Sun and applied an f-2 correction for ionospheric refraction. Our method retains the dispersion of source position with frequency, which is inherent in the radio source, but allows for the f-2 ionospheric effect. We also discuss ways of estimating the absolute source positions from a knowledge of ionospheric density gradients. A typical example of ionospheric variations on solar records is shown in Figure 1(a). Here we have plotted the observed source positions on an f-2 scale. The measurements refer to a solar storm continuum burst which occurred on 1981 May 9 following an importance 2B flare at 08°N., 38°E., heliographic coordinates. From previous observations of such events we think it highly likely that the true source positions are stationary and displaced with decreasing frequency outwards along a line close to the radial direction above the flare. Figure 1(a) shows that: (a) the 160, 80 and 43 MHz source displacements vary as f-2; (b) there is a systematic slow drift of the source positions towards the south and east which increases with increasing hour angle; (c) superimposed on this steady drift is a quasi-periodic variation in source position with a period ~20 min.

Tomographic imaging of attenuation with simulation correction for refraction

Beam refraction in soft tissue and phase cancellation at the receiver can cause large errors and prevent tomographic reconstruction of attenuation. The method developed in this study incorporates simulation of ultrasound propagation into tomographic imaging to correct these effects. The method is based on input scan data of time-of-flight and received signal amplitude. The speed of propagation is estimated from the time-of-flight scan data. Based on this estimate, the simulation generates scan data of signal amplitude. This scan data represents the loss from refraction and phase cancellation with zero attenuation, and is used to correct the input amplitude scans. We evaluate the accuracy of the method, and investigate the trade-off between various scanning and filtering parameters. The evaluation is based on scan data generated by a comprehensive simulation including refraction, attenuation, phase cancellation, finite beam width, several target shapes and sizes with sound parameters consistent with biologic values, and discrete translational and rotational transducer positions. In several cases with large refraction distortions, attenuation images are accurately reconstructed which are not feasible using standard tomographic methods.