Accuracy Of Height Measurements Research Articles

Improving assessment of child growth in a pediatric hospital setting

BackgroundAccurate anthropometric measurements are essential for assessing nutritional status, monitoring child growth, and informing clinical care. We aimed to improve height measurements of hospitalized pediatrics patients through implementation of gold standard measurement techniques.MethodsA quality improvement project implemented computerized training modules on anthropometry and standardized wooden boards for height measurements in a tertiary children’s hospital. Heights were collected pre- and post-intervention on general pediatric inpatients under 5 years of age. Accuracy of height measurements was determined by analyzing the variance and by comparing to World Health Organization’s defined biologically plausible height-for-age z-scores. Qualitative interviews assessed staff attitudes.ResultsNinety-six hospital staff completed the anthropometry training. Data were available on 632 children pre- and 933 post-intervention. Training did not increase the proportion of patients measured for height (78.6% pre-intervention vs. 75.8% post-intervention, p = 0.19). Post-intervention, wooden height boards were used to measure height of 34.8% patients, while tape measures and wingspan accounted for 42.0% and 3.5% of measurements, respectively. There was no improvement in the quality of height measurements based on plausibility (approximately 3% height-for-age z-scores measurements flagged out of range pre- and post-intervention), digit preference (13.4% of digits pre- and 12.3% post-intervention requiring reclassification), or dispersion of measurements (height-for-age z-scores standard deviation 1.9 pre- and post-intervention). Staff reported that using the wooden board was too labor consuming and cumbersome.ConclusionsOur findings suggest that efforts to improve anthropometric measurements of hospitalized children have multiple obstacles, and further investigation of less cumbersome methods of measurements may be warranted.

IMPROVED TOPOGRAPHIC MAPPING IN VEGETATED MOUNTAINOUS AREAS BY HIGH-RESOLUTION RADARGRAMMETRY-ASSISTED SAR INTERFEROMETRY

Abstract. In densely vegetated mountainous areas, the height measurement accuracy of SAR interferometry is contaminated by phase unwrapping errors and volume scattering effects of the vegetation. Aiming at this limitation of InSAR, we propose the high-resolution radargrammetry-assisted SAR interferometry method to achieve high-precision topographic mapping. Specifically speaking, we propose to apply our methods in the TerraSAR-X images with a repeat-pass InSAR pair and a stereo radargrammetric pair sharing the same master image which can avoid radarcoding the reference DEM and minimize the acquisition time discrepancy between the reference DEM and InSAR data. Compared with medium-resolution reference DEM, the high-resolution radargrammetric DEM can simulate the reference topographic phase more accurately which reduces the InSAR phase unwrapping errors. In addition to the removal of the reference topographic phase, we automatically select reliable points from radargrammetric DEM for calibrating the absolute InSAR phase offset. Finally, we fuse the radargrammetric DEM and InSAR DEM together with weights determined from theoretical height error to fill in data voids in InSAR DEM. The experimental results show that the DEM generated by radargrammetry-assisted SAR interferometry has better height accuracy than DEM generated by either single method.

Modeling Salt Marsh Vegetation Height Using Unoccupied Aircraft Systems and Structure from Motion

Salt marshes provide important services to coastal ecosystems in the southeastern United States. In many locations, salt marsh habitats are threatened by coastal development and erosion, necessitating large-scale monitoring. Assessing vegetation height across the extent of a marsh can provide a comprehensive analysis of its health, as vegetation height is associated with Above Ground Biomass (AGB) and can be used to track degradation or growth over time. Traditional methods to do this, however, rely on manual measurements of stem heights that can cause harm to the marsh ecosystem. Moreover, manual measurements are limited in scale and are often time and labor intensive. Unoccupied Aircraft Systems (UAS) can provide an alternative to manual measurements and generate continuous results across a large spatial extent in a short period of time. In this study, a multirotor UAS equipped with optical Red Green Blue (RGB) and multispectral sensors was used to survey five salt marshes in Beaufort, North Carolina. Structure-from-Motion (SfM) photogrammetry of the resultant imagery allowed for continuous modeling of the entire marsh ecosystem in a three-dimensional space. From these models, vegetation height was extracted and compared to ground-based manual measurements. Vegetation heights generated from UAS data consistently under-predicted true vegetation height proportionally and a transformation was developed to predict true vegetation height. Vegetation height may be used as a proxy for Above Ground Biomass (AGB) and contribute to blue carbon estimates, which describe the carbon sequestered in marine ecosystems. Employing this transformation, our results indicate that UAS and SfM are capable of producing accurate assessments of salt marsh health via consistent and accurate vegetation height measurements.

ANALISIS HASIL PENGUKURAN TINGGI TAKHIMETRI DENGAN SIPAT DATAR TELITI

This study is to analyze the accuracy of height measurements using the Waterpass as high measurement of height and Kolida Theodolite DT 02. The location of the study was conducted in the Cawang Campus UKI area in November 2018. 
 The method used is the measurement of the different height of polygon with a closed-loop by using Waterpass B2 and Kolida DT 02 Theodolite by using Tachymetri. Measurements are made three times with different loop, with the starting point and the end are the same point. 
 The results showed that the calculation of the high closing error in rings 1, 2 and 3 with the Waterpass were 1 mm, 4 mm and 6 mm respectively. Whereas the high closing error with Theodolite Kolida DT 02 is12mm, 6mm, 19mm respectively. The Standard deviation of height difference with Waterpass is 1mm while with Theodolite 19mm. The conclusion that can be drawn is the Theodolite Kolida DT 02 can be used for high measurements in jobs that are not required to be very high accuracy.
 
 Keywords : Tachymetri:high measurement;accuracy
 
 

Reliability and agreement of a novel portable laser height metre.

Human height is a simple measure with great applicability. Usually, stadiometers are used to measure height accurately. However, these may be impractical to transport and expensive. Therefore, we developed a portable and low-cost laser height metre (LHM). We aimed to (1) determine intrarater and interrater reliability of our LHM and compare it to a wall-fixed stadiometer, (2) examine its agreement with the same stadiometer, and (3) determine the minimum number of recordings needed to obtain an accurate and reliable height measurement using the LHM. We recruited 32 participants (18+ years)-both men and women. Two raters performed assessments on the same day blinded to each other and their reference standard measurements. We calculated intraclass correlation coefficient (ICC), coefficient of variation (CV), standard error of measurement (SEM), and Bland-Altman plots with limits of agreement (LOA). For both the LHM and stadiometer, we found ICC values of 0.99-1.00 (95% CI: 0.997-1.000) for both intrarater and interrater reliability. Regarding LHM intrarater reliability, SEM, CV, and LOA were 0.34 cm, 0.16%, and -1.07 to 0.73 cm, respectively. In terms of LHM interrater reliability, SEM, CV, and LOA were 0.27 cm, 0.12%, and -0.32 to 0.84 cm, respectively. As to agreement with stadiometers using one measurement, the mean difference was -0.14 cm and LOA ranged from -0.81 to 0.77 cm. A portable and low-cost LHM, for measuring body height once, showed an excellent reproducibility within and between raters along with an acceptable agreement with a stadiometer thereby representing a suitable alternative.

Normal and Abnormal Growth in the Pediatric Patient

Proper growth is a marker of the overall health of a child. Growth monitoring in infancy and childhood is a central part of preventative child health programs. For early recognition of pathological causes of growth failure, accurate measurements of height and weight using standardized methods is fundamental. The general pediatrician is a key participant, as he/she provides the auxological data to determine if further testing is needed. This review provides an outline for the general pediatrician for proper auxological measurements, normal variants versus abnormal growth, initial testing for abnormal growth, and when to refer to a pediatric endocrinologist.

Modeling the Optimal Baseline for a Spaceborne Bistatic SAR System to Generate DEMs

Interferometric synthetic aperture radar (InSAR) is one of the best methods for obtaining digital elevation models (DEMs). However, the problem of the uncertainty of DEM accuracy affected by the perpendicular baseline still persists, which should be as long as possible to ensure the sensitivity of the phase to the height measurement, and as small as possible to ensure a high spatial coherence. Moreover, the baseline configuration design of bistatic SAR system lacks a more detailed model for reference to generate high-precision DEM. Therefore, in this paper, the optimal baseline is modeled to maximize the accuracy of height measurement. First, we analyze the influence of system parameters on the height measurement accuracy, and a propagation model from the parameter estimation error to the elevation error is derived. Then, the phase unwrapping error (PUE) that considers the spatial baseline coherence, terrain slope and phase unwrapping effectiveness is modeled and analyzed after interferometric phase simulation and adaptive unscented Kalman filter phase unwrapping. Combining the relationship between the height error and the PUE, the optimal baseline model is obtained by statistical analysis. Finally, weighted averages are used to calculate the average slope of the complex terrain and the validity and reliability of the proposed optimal baseline model are verified by two examples of complex terrains with uniformly and nonuniformly distributed positive and negative slope angles. Moreover, the optimal baseline ranges of different terrain types are also derived for reference.

Influence of the structure of cylindrical mobile flumes on hydraulic performance characteristics in U-shaped channels

Small U-shaped channels are widely used in irrigation districts. Accurate flow measurement in U-shaped channels is an important aspect to field water management. In open channels, mobile flumes are widely used for flow measurement because of many advantages such as low cost, no sedimentation and moveable. However, how the structure of the flume influences hydraulic performance is still unclear. The principles for designing or optimizing mobile flumes are also lacking. In this study, FLOW-3D software was used to numerically simulate the flow pattern of three cylindrical mobile flumes that are most often used in U-shaped channels, including circular cylinder, elliptical cylinder and V-tailed cylinder mobile flumes. The hydraulic characteristics including backwater height, energy loss and flow measurement accuracy were analyzed. The results showed that under the same working conditions, the fluctuations of the stagnation point depth in the elliptical flume were the smallest. The backwater height and the energy loss in the V-tailed flume were the lowest. The contraction section of the cylinder could be designed as a curve with large curvature to make the upstream water flow more stable. The diffusion section could be designed as V-tail to improve flow pattern and reduce energy loss. Under a safe backwater height, the throat length could be increased to improve the submergence degree.

Research on equivalent height compensation measurement method of UHF partial dispenser based on GTEM cell

Based on the GTEM chamber for the equivalent height detection method of UHF partial discharge tester, this paper simulates the electric field at the top of the GTEM window. The results show that the electric field strength changes significantly along the position of the top fenestration axis. This change will have a non-negligible effect on the accuracy of the UHF partial discharge equivalent height measurement. In this way, an equivalent height compensation method for the UHF partial discharge tester is proposed. The method compensates for the electric field of the reference sensor position by using the electric field of the measured sensor position as a standard. Through the comparison before and after compensation, the method can effectively improve the accuracy of the equivalent height measurement of the UHF partial discharge tester.

Ionospheric Influence on Height Measurement Accuracy in Two-Pass Ground Survey Using P-Band Bistatic Radar System

In this letter, a theoretical study of the ionospheric influence on the accuracy of measuring the terrain height using a bistatic interferometer composed of a P-band synthetic aperture space radar and a ground receiver was carried out. A method for calculating the height measurement error that takes into account the interferometer geometry, the influence of the ionosphere parameters, additive noise, and spatial decorrelation of radar images is presented. The numerical dependences are obtained that allow estimating the optimal range of the interferometric base values and the height measurement error for point and extended targets.

The performance of CryoSat-2 fully-focussed SAR for inland water-level estimation

This paper applies the Fully-Focussed SAR (FF-SAR) algorithm to CryoSat-2 full-bit-rate data to measure water levels of lakes and canals in the Netherlands, and validates these measurements by comparing them to heights measured by gauges. Over Lake IJssel, a medium-sized lake, the FF-SAR height is biased about 6 cm below the gauge height, and a similar bias is found at six sites where CryoSat-2 crosses rivers and canals. The precision of the FF-SAR measurements depends on the extent of multi-looking (incoherent averaging along-track) applied. Over Lake IJssel the precision varies from 4 to 11 cm, decreasing as multi-looking increases. The precision of FF-SAR with 100 m of multi-looking is equivalent to that of the standard delay/Doppler processing, which has an along-track resolution of about 300 m. The width and orientation of rivers and canals limits the maximum available multi-looking. After removing the 6 cm bias, FF-SAR heights of rivers and canals have an accuracy between 2 cm and several decimeters, primarily depending on the presence of other water bodies lying within the cross-track measurement footprint, as these contaminate the waveform. We demonstrate that FF-SAR processing is able to resolve and measure small ditches only a few meters in width. The visibility of these signals depends on the angle at which CryoSat-2 crosses the ditch and on whether or not the ditch remains straight within CryoSat-2’s field of view. In the best-case scenario, straight ditches at nearly 90° to the CryoSat-2 ground track, the ditch signal has high enough signal-to-noise to allow sub-decimeter accuracy of FF-SAR height measurement.

High-Resolution Bathymetry Mapping of Water Bodies: Development and Implementation

Traditionally, bathymetry mapping of ponds, lakes, and rivers have used techniques which are low in spatial resolution. Waste stabilisation ponds (WSPs) are utilised 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 techniques such as the 'sludge judge' and the 'white towel' test. Both of these methods have low spatial resolution, are subjective in terms of precision and accuracy, are labour intensive, and require a high level of safety precautions. A sonar device fitted to a remotely operated vehicle (ROV) can improve the resolution and accuracy of sludge height measurements, as well as reduce labour and safety requirements. This technology is readily available; however, despite its applicability, it has not been previously assessed for use on WSPs. This study aimed to design, build, and assess the performance of an ROV to measure sludge height in WSPs. Profiling of several WSPs has shown that the ROV with autonomous sonar device is capable of providing bathymetry with greatly increased spatial resolution in a greatly reduced profiling time. To date, the ROV has been applied on in excess of 400 WSPs across Australia, several large lakes, stormwater retention ponds, river beds, and drinking water reservoirs. ROVs, such as the one built in this study, will be useful for not only determining sludge profiles, but also in calculating sludge accumulation rates and in evaluating pond hydraulic efficiency. As demonstrated, this technology is not limited to application in wastewater management, with the potential for wider application in the monitoring of other small to medium sized water bodies, including reservoirs, lakes, channels, recreational water bodies, river beds, mine tailing dams and commercial ports.

카메라를 이용한 공작물 크기 측정시스템 설계

In this paper, the workpiece size measurement system is designed to measure the size (width and height) of a workpiece using the measurement system with a camera. The system consists of a body, a vertical camera movement mechanism, a horizontal camera focus adjustment mechanism, a horizontal illumination device, a vertical illumination device, an infrared sensor, and a control device. To improve the measurement accuracy, camera calibration and image rotation calibration were performed, and image processing was performed using a subpixel algorithm. As a result of measuring the width and height of the block gauges as a reference object using the workpiece size measurement system, the width measurement accuracy was ±0.0041 mm and the height measurement accuracy was ±0.0043 mm. Therefore, it is considered that the designed workpiece size measurement system can measure a workpiece with accuracy less than ± 0.01.

Measurement of the bone height of mandibular incisors and canines on computed tomography-Limitations according to bone thickness.

To verify the correlation between cone beam CT (CBCT) and spiral CT (SCT) images and direct measurement of the bone height and to verify whether bone thickness (BT) influences the accuracy of bone height measurement on CT. One hundred and fourteen measurements were obtained in 10 dry human mandibles. The alveolar bone height was measured on volumetric and linear images. Negative, average and significant correlations (-0.622** to -0.489**) were verified between BT and the absolute error. When the alveolar bone thickness was at least 0.6mm, the mean differences were 0.16 and 0.28mm on linear images and 0.12 and 0.03mm on volumetric images for CBCT and SCT. Additionally, these values ranged from -0.46 to 0.79 and -0.32 to 0.88mm on linear images and from -0.64 to 0.67 and -0.57 to 0.62mm on volumetric images for CBCT and SCT. When the alveolar bone thickness was less than 0.6mm, the CT evaluation varied from -1.74 to 5.42 and -1.64 to 5.42mm on linear images and from -3.70 to 4.28mm and -3.49 to 4.25mm on volumetric images for CBCT and SCT. Spiral CT and CBCT images demonstrate significant correlation with direct measurement for the alveolar bone height. Measurement of the alveolar bone labial and lingual to the mandibular incisors and canines presented higher accuracy when its thickness was greater than 0.6mm. When the thickness was less than 0.6mm, bone dehiscence can be diagnosed despite bone being clinically present.

Structure from motion photogrammetry in ecology: Does the choice of software matter?

Image‐based modeling, and more precisely, Structure from Motion (SfM) and Multi‐View Stereo (MVS), is emerging as a flexible, self‐service, remote sensing tool for generating fine‐grained digital surface models (DSMs) in the Earth sciences and ecology. However, drone‐based SfM + MVS applications have developed at a rapid pace over the past decade and there are now many software options available for data processing. Consequently, understanding of reproducibility issues caused by variations in software choice and their influence on data quality is relatively poorly understood. This understanding is crucial for the development of SfM + MVS if it is to fulfill a role as a new quantitative remote sensing tool to inform management frameworks and species conservation schemes. To address this knowledge gap, a lightweight multirotor drone carrying a Ricoh GR II consumer‐grade camera was used to capture replicate, centimeter‐resolution image datasets of a temperate, intensively managed grassland ecosystem. These data allowed the exploration of method reproducibility and the impact of SfM + MVS software choice on derived vegetation canopy height measurement accuracy. The quality of DSM height measurements derived from four different, yet widely used SfM‐MVS software—Photoscan, Pix4D, 3DFlow Zephyr, and MICMAC, was compared with in situ data captured on the same day as image capture. We used both traditional agronomic techniques for measuring sward height, and a high accuracy and precision differential GPS survey to generate independent measurements of the underlying ground surface elevation. Using the same replicate image dataset (n = 3) as input, we demonstrate that there are 1.7, 2.0, and 2.5 cm differences in RMSE (excluding one outlier) between the outputs from different SfM + MVS software using High, Medium, and Low quality settings, respectively. Furthermore, we show that there can be a significant difference, although of small overall magnitude between replicate image datasets (n = 3) processed using the same SfM + MVS software, following the same workflow, with a variance in RMSE of up to 1.3, 1.5, and 2.7 cm (excluding one outlier) for “High,” “Medium,” and “Low” quality settings, respectively. We conclude that SfM + MVS software choice does matter, although the differences between products processed using “High” and “Medium” quality settings are of small overall magnitude.

UAV-Based High-Throughput Approach for Fast Growing Cunninghamia lanceolata (Lamb.) Cultivar Screening by Machine Learning

Obtaining accurate measurements of tree height and diameter at breast height (DBH) in forests to evaluate the growth rate of cultivars is still a significant challenge, even when using light detection and ranging (LiDAR) and three-dimensional (3-D) modeling. As an alternative, we provide a novel high-throughput strategy for predicting the biomass of forests in the field by vegetation indices. This study proposes an integrated pipeline methodology to measure the biomass of different tree cultivars in plantation forests with high crown density, which combines unmanned aerial vehicles (UAVs), hyperspectral image sensors, and data processing algorithms using machine learning. Using a planation of Cunninghamia lanceolate, which is commonly known as Chinese fir, in Fujian, China, images were collected while using a hyperspectral camera. Vegetation indices and modeling were processed in Python using decision trees, random forests, support vector machine, and eXtreme Gradient Boosting (XGBoost) third-party libraries. The tree height and DBH of 2880 samples were manually measured and clustered into three groups—“Fast”, “median”, and “normal” growth groups—and 19 vegetation indices from 12,000 pixels were abstracted as the input of features for the modeling. After modeling and cross-validation, the classifier that was generated by random forests had the best prediction accuracy when compared to other algorithms (75%). This framework can be applied to other tree species to make management and business decisions.

Influence of pixelization on height measurement in atomic force microscopy

Though AFM is capable of obtaining sub-angstrom resolution in z-direction, the accurate height measurement of protruding particles is hindered by raster nature of this technique. In this work using Monte Carlo simulations we have quantified the influence of pixelization on the mean AFM apparent height (hmean) of spheres and cylinders. We have demonstrated that for a zero size AFM probe hmean may be increasing, decreasing function of a pixel size, or has more complex character depending on the standard deviation of a particle size. Therefore, AFM pixelization effects may induce both under- and overestimation of the true diameter. The observed complex behavior of hmean is explained by interplay of two opposing factors: the mismatch of the position of the “highest” pixel to the real topographical maximum and higher registration probabilities of larger particles. Consideration of the AFM probe size results in even bigger pixelization induced drops of hmean, which may amount to ∼50% of the true value. The obtained results contribute to AFM data interpretation and methodological aspects of AFM operation in many fields of nanoscience. In particular, they may be used for estimation of true height of nanoparticles from their AFM images obtained with different (even low) pixel resolution.

Measuring Tree Height with Remote Sensing—A Comparison of Photogrammetric and LiDAR Data with Different Field Measurements

We contribute to a better understanding of different remote sensing techniques for tree height estimation by comparing several techniques to both direct and indirect field measurements. From these comparisons, factors influencing the accuracy of reliable tree height measurements were identified. Different remote sensing methods were applied on the same test site, varying the factors sensor type, platform, and flight parameters. We implemented light detection and ranging (LiDAR) and photogrammetric aerial images received from unmanned aerial vehicles (UAV), gyrocopter, and aircraft. Field measurements were carried out indirectly using a Vertex clinometer and directly after felling using a tape measure on tree trunks. Indirect measurements resulted in an RMSE of 1.02 m and tend to underestimate tree height with a systematic error of −0.66 m. For the derivation of tree height, the results varied from an RMSE of 0.36 m for UAV-LiDAR data to 2.89 m for photogrammetric data acquired by an aircraft. Measurements derived from LiDAR data resulted in higher tree heights, while measurements from photogrammetric data tended to be lower than field measurements. When absolute orientation was appropriate, measurements from UAV-Camera were as reliable as those from UAV-LiDAR. With low flight altitudes, small camera lens angles, and an accurate orientation, higher accuracies for the estimation of individual tree heights could be achieved. The study showed that remote sensing measurements of tree height can be more accurate than traditional triangulation techniques if the aforementioned conditions are fulfilled.

UAS and Landsat imagery to determine fuel condition for fire behaviour prediction on spinifex hummock grasslands of arid Australia

ABSTRACTFlammable spinifex grasslands of arid Western Australia cover about 98 million hectares of the state, and large wildfires in this environment threaten biodiversity, life, property and cultural values. Understanding fire behaviour in spinifex grasslands informs prescribed burning and wildfire suppression activities. Unmanned aerial systems (UAS) are aiding in improving fire behaviour prediction by providing comprehensive and accurate measurements of vegetation cover, volume and height, the fuel characteristics of vegetation that influence fire behaviour. Classification of spinifex cover derived from UAS image capture has been compared to field transects. Data from UAS align better with Landsat satellite imagery than fuel cover measures from field transects. A good correlation was found between UAS-derived vegetation cover and Landsat imagery, which means satellite imagery can be used with confidence to estimate and map fuel cover at a range of temporal and spatial scales. UAS have also proven useful in the development of a spectral index describing spinifex cover. The rapid development of affordable UAS instruments and software has enabled the production of point clouds, which provide further vegetation structure information not available from previous image captures. These developments in UAS application together with satellite imagery will enable fire managers to more efficiently and accurately map fuel characteristics at a range of scales, greatly enhancing their ability to forecast fire danger and to predict fire behaviour without having to carry out costly ground-based field measurements.

Non‐uniform phase filter for Tiangong‐2 Interferometric Imaging Radar Altimeter

The interferometric imaging radar altimeter (InIRA) on-board Chinese Tiangong-2 space laboratory is a Ku-band interferometric radar whose major aim is to measure the wide-swath ocean topography. Unlike traditional interferometric synthetic aperture radar (InSAR) aiming at measuring digital elevation model of land surface, Tiangong-2 InIRA adopts small incidence angles and short baseline to get strong and high coherency reflections from ocean surface. The interferometric phase noise is a notable source of errors which limits the accuracy of the ocean height measurements. Compared with traditional InSAR, the height error of Tiangong-2 InIRA shows different distribution pattern due to the absolutely small but relatively large variation incidence angles. This study gives a filtering method for interferometric phase generated with small incidence angles and short baseline. Non-uniform windows are selected according to the relation between the coherence, imaging geometry, and the height variation. Results on Tiangong-2 InIRA data are analysed by comparing the non-uniform filtering method with traditional multi-looking method.