Accuracy Of Height Measurements Research Articles

Sea surface height measuring using InSAR altimeter

Satellite altimetry has been widely used in measuring ocean topography from space. The conventional altimeter system is the nadir radar altimeter system which has the limitations of one-dimensional measurement and is unable to get both high temporal and spatial resolution. The InSAR altimetry system using InSAR altimeter instead of nadir radar altimeter is an improvement which can get both high cross-track and along-track resolution and wide swath. However, the conventional SAR interferometry only can achieve meter level height accuracy. This paper focuses on a method of radar echo-tracking for InSAR altimeter system in order to correct the slant range measurements and finally to improve the height measurement accuracy to several centimeters' level. Radar slant range (from observed pixels to radar antenna) estimation error affects the height measurement accuracy badly, nevertheless not considered in the conventional SAR interferometry. The proposed method is ameliorated based on the traditional echo-model used in nadir radar altimeter system, focusing on the echo signals from observed pixels with different incident angles. Simulations of sea surface height measurements are performed in the last part of this paper, and the conclusions are drawn that, with corrected slant range, the accuracy of InSAR altimetry can be much better than the conventional SAR interferometry.

The technique of measuring the height in patients with osteoporosis

Introduction: In patients with osteoporosis, the loss of height is indicative of vertebral fractures and periodic height measurement is an essential component of their clinical assessment. It is a challenging task in these patients and there is no recommended, standard technique for measuring the height of these patients. Our objective was to assess the accuracy of the stadiometer and the drop-down scale with the carpenter’s level for height measurements. Method: Height measurements were taken from 30 consecutive patients using the stadiometer and the drop-down scale with carpenter’s scales. Again, three height measurements were taken from 172 patients using only the drop-down scale with carpenter’s scale. Results: The height measurements from stadiometer gave more accurate results compared to drop-down scale (p Conclusions: The stadiometer with a carpenter’s level can provide accurate height measurements in patients with osteoporosis. The accuracy of a single measurement is as good as the average of three height measurements.

4-D imaging of the short scale ocean waves using a slit streak tube imaging Lidar

A flash Lidar system based on a slit streak tube receiver has been developed and its functionality demonstrated for oceanographic and coastal measurements. Especially, the slit Streak Tube Imaging Lidar (STIL) can image the short scale sea-wave because of its high frame rate and good 4-D (3-D range+1-D intensity) image quality. From the range information supplied by STIL, accuracy of sea-wave height measurement is about centimeter level. In the paper, we calculate the echo power so that STIL carried by plane can image the ocean surface. Measurements of the short scale surface wave fields in the Yellow Sea and Bohai Sea are analyzed and discussed. We experimentally demonstrate that STIL can detect the short scale surface waves with high resolution.

Etching of Cr tips for scanning tunneling microscopy of cleavable oxides.

We report a detailed three-step roadmap for the fabrication and characterization of bulk Cr tips for spin-polarized scanning tunneling microscopy. Our strategy uniquely circumvents the need for ultra-high vacuum preparation of clean surfaces or films. First, we demonstrate the role of ex situ electrochemical etch parameters on Cr tip apex geometry, using scanning electron micrographs of over 70 etched tips. Second, we describe the suitability of the in situ cleaved surface of the layered antiferromagnet La1.4Sr1.6Mn2O7 to evaluate the spin characteristics of the Cr tip, replacing the ultra-high vacuum-prepared test samples that have been used in prior studies. Third, we outline a statistical algorithm that can effectively delineate closely spaced or irregular cleaved step edges, to maximize the accuracy of step height and spin-polarization measurements.

3D POSITION MEASUREMENT SIMULATION OF AIR TARGET'S SCATTERRERS IN INTERFEROMETRIC ISAR

If one introduces an additional antenna spaced apart in height in inverse synthetic aperture radar (ISAR) it is possible to carry out an interferometric measurement of the scatterers’ heights. The theoretical relation for estimating the accuracy of the scatterer height measurement is obtained. A simulation model for obtaining the three-dimensional radar images (RI) of air objects in interferometric ISAR was developed. The comparison of the scatterer height measurements accuracy by theoretical relation and the results of simulation at different SNRs are performed

CHARACTERISTICS OF AIRBORNE INTERFEROMETRIC SYNTHETIC APERTURE RADAR WITH SECTOR SCAN

One of the drawbacks of airborne interferometric synthetic aperture radar is a relatively narrow swath compared to analogous space based systems. Increasing the swath with side view of the interferometer can be possible by increasing the flight altitude and angle of sight. At the same time the height measurement accuracy decreases due to slant range distance increase. Another possible way of swath increasing is using sector scan. The efficiency of sector scan using in interferometric synthetic aperture radar is analyzed in this paper. The mathematical model and geometry of height measurement at a sector scan have been discussed. There was made an analysis of the effect of terrain height and observation angle on received signal phase changing. Observation angle changing is shown to contribute to the phase changing. Potential height accuracy measurement was calculated. The calculation results show that increasing the observation angle reduces height accuracy measurement. The maximum accuracy decrease is obtained at the observation angle of 90°. Despite height accuracy measurement decrease applying the sector scan allow to expand the swath. The accuracy decrease can be limited by selecting optimal parameters of scanning.

Sludge accumulation and distribution impact the hydraulic performance in waste stabilisation ponds

Waste stabilisation ponds (WSPs) are used worldwide for wastewater treatment, and throughout their operation require periodic sludge surveys. Sludge accumulation in WSPs can impact performance by reducing the effective volume of the pond, and altering the pond hydraulics and wastewater treatment efficiency. Traditionally, sludge heights, and thus sludge volume, have been measured using low-resolution and labour intensive methods such as ‘sludge judge’ and the ‘white towel test’. A sonar device, a readily available technology, fitted to a remotely operated vehicle (ROV) was shown to improve the spatial resolution and accuracy of sludge height measurements, as well as reduce labour and safety requirements. Coupled with a dedicated software package, the profiling of several WSPs has shown that the ROV with autonomous sonar device is capable of providing sludge bathymetry with greatly increased spatial resolution in a greatly reduced profiling time, leading to a better understanding of the role played by sludge accumulation in hydraulic performance of WSPs. The high-resolution bathymetry collected was used to support a much more detailed hydrodynamic assessment of systems with low, medium and high accumulations of sludge. The results of the modelling show that hydraulic performance is not only influenced by the sludge accumulation, but also that the spatial distribution of sludge plays a critical role in reducing the treatment capacity of these systems. In a range of ponds modelled, the reduction in residence time ranged from 33% in a pond with a uniform sludge distribution to a reduction of up to 60% in a pond with highly channelized flow. The combination of high-resolution measurement of sludge accumulation and hydrodynamic modelling will help in the development of frameworks for wastewater sludge management, including the development of more reliable computer models, and could potentially have wider application in the monitoring of other small to medium water bodies, such as channels, recreational water bodies, and commercial ports.

Decoupling criterion based on limited energy loss condition for groove measurement using optical scanning microscopes

In confocal metrology, the lateral and axial responses are coupled in narrow regions near groove edges. This coupling results in an area with an uncertain profile, particularly for measurements of tight structures or deep grooves. In this paper, to delineate the area with measurement accuracy loss, an analytical model depicting the coupling relationships between the groove depth, the coupled portions and the NA of the objective used is introduced. Based on this model, the limited energy lost (LEL) decoupling criterion is presented that can enable users to choose suitable numerical apertures before performing measurements, predict the extents of the areas with measurement accuracy loss, and identify readout areas that yield accurate height measurements. The theory was verified by using confocal microscopes and is also applicable to far-field optical scanning metrology.

Relationship Between Body Fat and Physical Fitness in Army ROTC Cadets.

The Army Physical Fitness Test (APFT), including timed push-ups, sit-ups, and run, assesses physical performance for the Army. Percent body fat is estimated using height and circumference measurements. The objectives of the study were to (a) compare the accuracy of height and circumference measurements to other, more accepted, body fat assessment methods and (b) determine the relationships between body composition and APFT results. Participants included Reserve Officer Training Corps (ROTC) cadets (n = 11 males, 2 females, 21.6 ± 3.5 years) from a midwestern university). At one visit, percent body fat was assessed using height and circumference measurements, air-displacement plethysmography, and bioelectrical impedance analysis. APFT results were provided by the ROTC director. All assessment methods for percent body fat were strongly associated (r ≥ 0.7, p < 0.01), implying that height and circumference measurement is a practical tool to estimate percent body fat of ROTC cadets. Total APFT score was not associated with any body fat assessment method. Push-up number was negatively associated with percent body fat by all assessment methods (r ≥ -0.8, p = 0.001), although run time was positively associated (r ≥ 0.6, p < 0.05). This suggests that percent body fat may be an important variable in determining or improving cardiovascular and muscular endurance, but not APFT performance.

Clinical height measurements are unreliable: a call for improvement.

Height measurements are currently used to guide imaging decisions that assist in osteoporosis care, but their clinical reliability is largely unknown. We found both clinical height measurements and electronic health record height data to be unreliable. Improvement in height measurement is needed to improve osteoporosis care. The aim of this study is to assess the accuracy and reliability of clinical height measurement in a university healthcare clinical setting. Electronic health record (EHR) review, direct measurement of clinical stadiometer accuracy, and observation of staff height measurement technique at outpatient facilities of the University of Wisconsin Hospital and Clinics. We examined 32 clinical stadiometers for reliability and observed 34 clinic staff perform height measurements at 12 outpatient primary care and specialty clinics. An EHR search identified 4711 men and women age 43 to 89 with no known metabolic bone disease who had more than one height measurement over 3months. The short study period and exclusion were selected to evaluate change in recorded height not due to pathologic processes. Mean EHR recorded height change (first to last measurement) was -0.02cm (SD 1.88cm). Eighteen percent of patients had height measurement differences noted in the EHR of ≥2cm over 3months. The technical error of measurement (TEM) was 1.77cm with a relative TEM of 1.04%. None of the staff observed performing height measurements followed all recommended height measurement guidelines. Fifty percent of clinic staff reported they on occasion enter patient reported height into the EHR rather than performing a measurement. When performing direct measurements on stadiometers, the mean difference from a gold standard length was 0.24cm (SD 0.80). Nine percent of stadiometers examined had an error of >1.5cm. Clinical height measurements and EHR recorded height results are unreliable. Improvement in this measure is needed as an adjunct to improve osteoporosis care.

Comparison of Wave Height Measurement Algorithms for Ship-Borne X-Band Nautical Radar

. In this article, a comparison of signal-to-noise ratio (SNR) and shadowing-based algorithms for ocean wave height estimation from ship-borne X-band nautical radar sea surface images is presented. Modifications, including selecting a subarea along the upwind direction and smoothing the edge pixel intensity histogram, are made to the original shadowing algorithm to achieve more accurate wave height measurements. Tests of the algorithms are conducted using radar and buoy data acquired in a sea trial in the North Atlantic Ocean off the east coast of Canada. Compared with the original shadowing algorithm, the modified algorithm improves the wave height estimation with a decrease of about 1.70 m in the root mean square (RMS) difference with respect to in situ measurements. In addition, the result of the comparison shows that the modified shadowing algorithm produces more accurate wave heights than the SNR method with improvements of about 0.05 in the correlation coefficient and about 0.04 m in the RMS difference.

Practicing Inter-Professional Teamwork among Nursing and Medical Students

Learning how to work effectively on inter-professional teams has been identified as an outcome competency in nursing education as specified by the Quality and Safety Education in Nursing Teamwork and Collaboration Competency [1] and in medical education as specified in the Liaison Committee on Medical Education [2]. How to teach teamwork skills, and where to place this content in the curriculum, is an ongoing problem for both medicine and nursing. The purpose of this paper is to describe the development and evaluation of a community work-place learning activity that evolved from a nursing student experience to an interprofessional experience. Background: Nursing students from a large midwestern research university had been participating in a health screening research project of school children supported by the Elisabeth Severance Prentiss Foundation of their community health courses. Learning objectives for each course were broad with very little differentiation between levels. Using concept-based curriculum principles, and content from the Team STEPPS in 2006 national program, the courses were restructured and an interprofessional teamwork experience for nursing and medical students was implemented. All students participated in an extensive orientation that required each one to pass skills tests for taking an accurate blood pressure and performing accurate height and weight measurements. Nursing students were educated at two different levels: junior nursing students lead the activity while sophomore students focused on health screenings data collection and assessment. Previous to the restructuring, the team leader role was assumed by faculty. With role clarification, faculty shifted their function to the role of a team coach. Medical students were trained much like sophomore nursing students with the role of carrying out clinical tasks. Following each interprofessional teamwork experience, students completed the Interprofessional Collaborative Competencies Attainment Survey (ICCAS). IRB determined this to be exempt from review. Results: An Independent sample t-test was used to compare mean score differences. Mean score differences on the ICCAS between inter-professional collaborative competencies before and after the experience for 122 participants showed a significant improvement between Total pre-mean score (M=116.5, SD=19.1) and Total post mean score (M=127.6, SD=15.2); t=8.5, p<0.001. Additionally, all ICCAS subcategories (Communication, Collaboration, Roles and Responsibilities, Collaborative Patient/Family Centered Approach, Conflict Management, Team Functioning) showed a significant difference between pre and post mean score differences. Conclusion: The public health screening project funded by the Prentis grant was effective in learning interprofessional collaborative competencies while meeting nursing and medical student course learning objectives. Faculty creatively working together can overcome the obstacles to inter-professional education to promote learning teamwork and collaboration.

Laboratory Height And Weight Measurments In Collegiate American Football Players Compared To Athletic Program Measurements

Actual body weight and height for college athletes may be different than the weights and heights listed in an athletic program and/or media guides. Often heights and weights will be higher, than actual values, as an intimidation factor. PURPOSE: The purpose of this study was to compare the accuracy of laboratory body weight and height measurements in collegiate American football players to the height and weight measurements listed in the University football media guide. METHODS: Height (m) and weight (Kg) were measured by using a wall-mounted standiometer and body mass was measured using an electronic scale (Tanita BF-350, Arlington Heights, Illinois). These measurements were then compared to the height and weight listed in the University football media guide. Participants were 89 collegiate football players age 19.6 (1.4) years. Positions played by the participants varied between linemen (35) and non-linemen (54). An independent samples t-test was performed using SPSS (v.22) to analyze the difference between height and weight between the two sources. RESULTS: Laboratory height measurements 1.85 (.06) m and program height measurements 1.84 (.06) m were significantly different [t(88) = 5.803, p<.001]. Laboratory weight measurements 104.30 (17.64) kg and program weight measurements 104.95 (18.03) kg were significantly different [t(88) = -2.134, p=.036]. CONCLUSIONS: In this study, the laboratory measurements of both height and weight were found to be significantly different than the height and weight measurements found in the University football media guide. Also, the University game day program weight measurements were higher than the laboratory weight measurements, as was expected. However, the University game day program height measurements were lower than the height measurements in the laboratory, which was unexpected. Therefore, this study suggests that accurate measurements are not always displayed in athletic programs and/or media guides.

Symphysis-fundus height measurement to predict small-for-gestational-age status at birth: a systematic review.

BackgroundFetal growth restriction is among the most common and complex problems in modern obstetrics. Symphysis-fundus (SF) height measurement is a non-invasive test that may help determine which women are at risk. This study is a systematic review of the literature on the accuracy of SF height measurement for the prediction of small-for-gestational-age (SGA) status at birth in unselected and low-risk pregnancies.MethodsThe Medline, Embase, Cinahl, SweMed, and Cochrane Library databases were searched with no limitation on publication date (through September 2014), which returned 722 citations. Two reviewers then developed a short list of 51 publications of possible relevance and assessed them using the following inclusion criteria: cohort study of test accuracy performed in a routine prenatal care setting; SF height measurement for all participants; classification of SGA, defined as birth weight (BW) < 10th, 5th, or 3rd percentile or ≥ one or two standard deviations below the mean; study conducted in Northern, Western, or Central Europe; USA; Canada; Australia; or New Zealand; and sufficient data for 2 × 2 table construction. Quality of the included studies was assessed in duplicate using criteria suggested by the Cochrane Collaboration. Review Manager 5.3 software was used to analyze the data, including plotting of summary receiver operating curve spaces.ResultsEight studies were included in the final dataset and seven were included in summary analyses. The sensitivity of SF height measurement for SGA (BW < 10th percentile) prediction ranged from 0.27 to 0.76 and specificity ranged from 0.79 to 0.92. Positive and negative likelihood ratios ranged from 1.91 to 9.09 and from 0.29 to 0.83, respectively.ConclusionsSF height can serve as a clinical indicator along with other clinical findings, information about medical conditions, and previous obstetric history. However, SF height has high false-negative rates for SGA. Clinicians must understand the limitations of this test.The protocol has been registered in the international prospective register of systematic reviews, PROSPERO (Registration No. CRD42014008928, http://www.crd.york.ac.uk/prospero/display_record.asp?ID=CRD42014008928).Electronic supplementary materialThe online version of this article (doi:10.1186/s12884-015-0461-z) contains supplementary material, which is available to authorized users.

Estimation of Aboveground Biomass Using Manual Stereo Viewing of Digital Aerial Photographs in Tropical Seasonal Forest

The objectives of this study are to: (1) evaluate accuracy of tree height measurements of manual stereo viewing on a computer display using digital aerial photographs compared with airborne LiDAR height measurements; and (2) develop an empirical model to estimate stand-level aboveground biomass with variables derived from manual stereo viewing on the computer display in a Cambodian tropical seasonal forest. We evaluate observation error of tree height measured from the manual stereo viewing, based on field measurements. RMSEs of tree height measurement with manual stereo viewing and LiDAR were 1.96 m and 1.72 m, respectively. Then, stand-level aboveground biomass is regressed against tree height indices derived from the manual stereo viewing. We determined the best model to estimate aboveground biomass in terms of the Akaike’s information criterion. This was a model of mean tree height of the tallest five trees in each plot (R2 = 0.78; RMSE = 58.18 Mg/ha). In conclusion, manual stereo viewing on the computer display can measure tree height accurately and is useful to estimate aboveground stand biomass.

Accuracy of self-reported and measured anthropometric data in the inpatient population.

Self-reported body mass index (BMI) is commonly used to assess nutritional status. The aim of the study was to assess the accuracy of self-reported and measured data obtained from the inpatient population. A total of 296 individuals admitted to five hospital wards were included in the study. Patients provided details of their height and weight, and measurements of height and weight were subsequently taken. BMI measurements were calculated from both the self-reported and the measured data. In general, the study participants overestimated their height and underestimated their weight. Older people and women were significantly more likely to overestimate their height, whereas better educated people were more likely to underestimate their weight. Inaccurate height and weight reporting led to BMI values being underestimated. The findings of this study support previously published research questioning the accuracy of self-reported height and weight measurements.

Development of instructions and tape measure to improve accuracy of parental report of preschool height (1024.5)

Accurate height measurements are essential to calculating BMI. An iterative process was used to develop materials to improve the accuracy with which parents in an obesity‐prevention program measured and reported child height. Phase A used brief, written, stepwise instructions that were cognitively tested, operationalized by parents using equipment provided by researchers, and refined using parent feedback and researcher observations after each of 3 testing rounds (n=6,13,5). Researcher and parent child height measurements did not differ significantly in Round 1 &amp; 2 (mean difference within +0.18”+0.58SD). Round 3 revealed instructions were too difficult for parents with less formal education. Phase B used a brief narrated video that was tested and refined over a series of 4 rounds (n=9,13,5,5; 56% had high school or less; 44% had some college). Common errors were not verifying TM straightness, hanging TM over a baseboard, not removing child shoes, not having child breath in‐out before taking measurements, and misreading fractions. The TM was revised to label each ¼” mark. The video was refined and retested until differences between researcher and parent measurements were within +0.38”+0.48SD in the last testing round. Compared to written instructions, parents rated the video as clearer (4.88±0.34 vs 4.5±0.75SD) and felt the video would improve their child height measurements (4.98±0.09SD vs 4.09±1.16SD).Grant Funding Source: Supported by USDA, National Institute of Food and Agriculture, Grant Number 2011‐68001‐30170

Multitemporal crop surface models: accurate plant height measurement and biomass estimation with terrestrial laser scanning in paddy rice

Appropriate field management requires methods of measuring plant height with high precision, accuracy, and resolution. Studies show that terrestrial laser scanning (TLS) is suitable for capturing small objects like crops. In this contribution, the results of multitemporal TLS surveys for monitoring plant height on paddy rice fields in China are presented. Three campaigns were carried out on a field experiment and on a farmer’s conventionally managed field. The high density of measurement points allows us to establish crop surface models with a resolution of 1 cm, which can be used for deriving plant heights. For both sites, strong correlations (each R 2 =0.91 between TLS-derived and manually measured plant heights confirm the accuracy of the scan data. A biomass regression model was established based on the correlation between plant height and biomass samples from the field experiment (R 2 =0.86 ). The transferability to the farmer’s field was supported with a strong correlation between simulated and measured values (R 2 =0.90 ). Independent biomass measurements were used for validating the temporal transferability. The study demonstrates the advantages of TLS for deriving plant height, which can be used for modeling biomass. Consequently, laser scanning methods are a promising tool for precision agriculture.

Cyclostationary empirical orthogonal function sea‐level reconstruction

Since 1993, satellite altimetry has provided accurate measurements of sea surface height with near‐global coverage. These measurements led to the first definitive estimates of global mean sea‐level (GMSL) rise and have improved understanding of how sea levels are changing regionally at decadal time scales. These relatively short records, however, provide no information about the state of the ocean prior to 1993, and with the modern altimetry record spanning only 20 years, the lower frequency signals that are known to be present in the ocean are difficult or impossible to resolve. Tide gauges, on the other hand, have measured sea level over the last 200 years, with some records extending back to 1807. While providing longer records, the spatial resolution of tide gauge sampling is poor, making studies of the large‐scale patterns of ocean variability and estimates of GMSL difficult. Combining the satellite altimetry with the tide gauges using a technique known as sea‐level reconstruction results in a dataset with the record length of the tide gauges and the near‐global coverage of satellite altimetry. Cyclostationary empirical orthogonal functions (CSEOFs), derived from satellite altimetry, are combined with historical sea‐level measurements from tide gauges to create the Reconstructed Sea Level dataset spanning from 1950 to 2009. Previous sea‐level reconstructions have utilized empirical orthogonal functions (EOFs) as basis functions, but by using CSEOFs and by addressing other aspects of the reconstruction procedure, an alternative sea‐level reconstruction can be computed. The resulting reconstructed sea‐level dataset has weekly temporal resolution and half‐degree spatial resolution.

Accurately Measuring the Height of (Real) Forest Trees

Q uick and accurate tree height measurement has always been a goal of foresters. The techniques and technology to measure height were developed long ago—even the earliest textbooks on mensuration showcased hypsometers (e.g., Schlich 1895, Mlodziansky 1898, Schenck 1905, Graves 1906), and approaches to refine these sometimes remarkable tools appeared in the first issues of Forestry Quarterly, Proceedings of the Society of American Foresters, and the Journal of Forestry. For example, one such hypsometer based on the geometric principle of similar triangles (top of Figure 1) employed rotary mirrors to allow the user to simultaneously see the top and bottom of the tree in “proper parallax” (Tieman 1904). Other early hypsometers applied different approaches that used angles and distance (e.g., Graves 1906, Detwiler 1915, Noyes 1916, Krauch 1918). Of these trigonometric hypsometers, those that calculated total tree height (HT) as a function of the tangent of the angles to the top (B2) and bottom (B1) of the tree and a baseline horizontal distance (b) to the stem were most common (Figure 1). Because they are easy to apply and required only simple technology, these approaches (hereafter, the similar triangles and tangent methods) have dominated tree height measurement. That is not to say the challenge of accurate tree height measurement was solved— many early foresters reported problems with getting consistent data in uneven terrain or dense understories or with the use of different types of hypsometers. Good measurement practices usually mitigated these issues and became standard components of forester training programs. Others addressed these challenges by designing new techniques based on different trigonometric relationships. As an example, Haig (1925) proposed a slide rule solution that calculated tree height using the sine law and slope distance from the observer to the tree base (s1)