scholarly journals Enhancing UAV–SfM 3D Model Accuracy in High-Relief Landscapes by Incorporating Oblique Images

2019 ◽  
Vol 11 (3) ◽  
pp. 239 ◽  
Author(s):  
Paul Nesbit ◽  
Christopher Hugenholtz
Keyword(s):  
Surface Deformation ◽  
Laser Scanner ◽  
Systematic Errors ◽  
Camera Angle ◽  
Processing Strategies ◽  
Accuracy And Precision ◽  
Complex Scenes ◽  
Precision And Accuracy ◽  
Oblique Images ◽  
Steep Slopes

Complex landscapes with high topographic relief and intricate geometry present challenges for complete and accurate mapping of both lateral (x, y) and vertical (z) detail without deformation. Although small uninhabited/unmanned aerial vehicles (UAVs) paired with structure-from-motion (SfM) image processing has recently emerged as a popular solution for a range of mapping applications, common image acquisition and processing strategies can result in surface deformation along steep slopes within complex terrain. Incorporation of oblique (off-nadir) images into the UAV–SfM workflow has been shown to reduce systematic errors within resulting models, but there has been no consensus or documentation substantiating use of particular imaging angles. To address these limitations, we examined UAV–SfM models produced from image sets collected with various imaging angles (0–35°) within a high-relief ‘badland’ landscape and compared resulting surfaces with a reference dataset from a terrestrial laser scanner (TLS). More than 150 UAV–SfM scenarios were quantitatively evaluated to assess the effects of camera tilt angle, overlap, and imaging configuration on the precision and accuracy of the reconstructed terrain. Results indicate that imaging angle has a profound impact on accuracy and precision for data acquisition with a single camera angle in topographically complex scenes. Results also confirm previous findings that supplementing nadir image blocks with oblique images in the UAV–SfM workflow consistently improves spatial accuracy and precision and reduces data gaps and systematic errors in the final point cloud. Subtle differences among various oblique camera angles and imaging patterns suggest that higher overlap and higher oblique camera angles (20–35°) increased precision and accuracy by nearly 50% relative to nadir-only image blocks. We conclude by presenting four recommendations for incorporating oblique images and adapting flight parameters to enhance 3D mapping applications with UAV–SfM in high-relief terrain.

scholarly journals 3D MODELING OF INDUSTRIAL HERITAGE BUILDING USING COTSs SYSTEM: TEST, LIMITS AND PERFORMANCES

2017 ◽  
Vol XLII-2/W6 ◽  
pp. 281-288 ◽  
Author(s):  
M. Piras ◽  
V. Di Pietra ◽  
D. Visintini
Keyword(s):  
New Technologies ◽  
Sensor Calibration ◽  
Industrial Heritage ◽  
Imaging Geometry ◽  
Processing Strategies ◽  
Two Factors ◽  
Industrial Architecture ◽  
Dense Point ◽  
Heritage Building ◽  
Oblique Images

The role of UAV systems in applied geomatics is continuously increasing in several applications as inspection, surveying and geospatial data. This evolution is mainly due to two factors: new technologies and new algorithms for data processing. About technologies, from some years ago there is a very wide use of commercial UAV even COTSs (Commercial On-The-Shelf) systems. Moreover, these UAVs allow to easily acquire oblique images, giving the possibility to overcome the limitations of the nadir approach related to the field of view and occlusions. In order to test potential and issue of COTSs systems, the Italian Society of Photogrammetry and Topography (SIFET) has organised the SBM2017, which is a benchmark where all people can participate in a shared experience. This benchmark, called “Photogrammetry with oblique images from UAV: potentialities and challenges”, permits to collect considerations from the users, highlight the potential of these systems, define the critical aspects and the technological challenges and compare distinct approaches and software. The case study is the “Fornace Penna” in Scicli (Ragusa, Italy), an inaccessible monument of industrial architecture from the early 1900s. The datasets (images and video) have been acquired from three different UAVs system: Parrot Bebop 2, DJI Phantom 4 and Flytop Flynovex. The aim of this benchmark is to generate the 3D model of the “Fornace Penna”, making an analysis considering different software, imaging geometry and processing strategies. This paper describes the surveying strategies, the methodologies and five different photogrammetric obtained results (sensor calibration, external orientation, dense point cloud and two orthophotos), using separately – the single images and the frames extracted from the video – acquired with the DJI system.

Validation of heart rate measurement of Fitbit Charge 4 and Xiaomi Mi Band 5 (Preprint)

2021 ◽  
Author(s):  
Magdalena Jachymek ◽  
Michał Tomasz Jachymek ◽  
Radosław Marek Kiedrowicz ◽  
Jarosław Kaźmierczak ◽  
Małgorzata Peregud-Pogorzelska
Keyword(s):  
Heart Rate ◽  
Stress Test ◽  
Absolute Error ◽  
Sensor Technology ◽  
Concordance Correlation ◽  
Accuracy And Precision ◽  
Validation Criteria ◽  
Precision And Accuracy ◽  
Fitness Trackers ◽  
Error Percentage

BACKGROUND Recent advances in mobile sensor technology have led to increased popularity of wrist-worn fitness trackers. The possibility to use a smartwatch as a rehabilitation tool to monitor patients’ heart rate during exercise has won the attention of many researchers. OBJECTIVE The aim of the study was to evaluate the accuracy and precision of HR measurement performed by two wrist monitors: Fitbit Charge 4 (Fitbit) and Xiaomi Mi Band 5 (Xiaomi). METHODS 31 healthy volunteers were asked to perform a stress test on a treadmill. During the test their heart rate was recorded simultaneously by both wristbands and ECG at 1minute intervals. The mean absolute error percentage (MAPE), Lin’s concordance correlation coefficient (LCCC) and Bland-Altman were calculated to compare precision and accuracy of heart rate measurements. The estimated validation criteria were MAPE < 10% and LCCC < .8 RESULTS The overall MAPE of the Fitbit device was 10.19% (±11.79%) and the MAPE of Xiaomi was (6.89 % ± 9.75). LCCC of Fitbit HR measurements was .753 (95% CI:0.717-0.785) and of Xiaomi – .903 (0.886-0.917). In both devices the precision and accuracy were decreasing with the increasing exercise intensity. Age, sex, height, weight, BMI did not influence the accuracy of both devices. CONCLUSIONS The accuracy of a wearable wrist-worn heart rate monitor varies and depends on the intensity of training. The decision concerning the application of such a device as a monitor during in-home rehabilitation should be taken with caution, as it may prove not reliable enough.

Technology of Manually Operated Sampler Pipets

1974 ◽  
Vol 20 (3) ◽  
pp. 320-323 ◽  
Author(s):  
Robert E Wenk ◽  
Jack A Lustgarten
Keyword(s):  
Environmental Conditions ◽  
Optimal Performance ◽  
Tolerance Limits ◽  
Accuracy And Precision ◽  
Operational Characteristics ◽  
Precision And Accuracy ◽  
Rapid Transfer

Abstract We have evaluated the performance of manually operated sampler pipets. Twenty-four instruments of various construction, manufacture, and delivery volume were evaluated. Pipet-delivered water and serum were repeatedly weighed under controlled environmental conditions, and precision and accuracy assessed. The pipets often failed to meet the manufacturer's stated tolerance limits. Consumers should calibrate these instruments in their own laboratories. Some of the manufacturer's recommendations for optimal performance are challenged. The manual samplers can substitute for oral pipets and permit safe, inexpensive, simple, and rapid transfer of liquids, if the user recognizes their operational characteristics and limitations in accuracy and precision.

scholarly journals 40Ar/39Ar geochronology at the Instituto de Geociências, USP: instrumentation, analytical procedures, and calibration

2002 ◽  
Vol 74 (2) ◽  
pp. 297-342 ◽  
Author(s):  
PAULO M. VASCONCELOS ◽  
ARTUR T. ONOE ◽  
KOJI KAWASHITA ◽  
ADALBERTO J. SOARES ◽  
WILSON TEIXEIRA
Keyword(s):  
Laser Heating ◽  
Spectrometric Analysis ◽  
Data Sets ◽  
Diverse Range ◽  
Mineral Separation ◽  
Accuracy And Precision ◽  
Precision And Accuracy ◽  
Analytical Procedures ◽  
Brazilian Students ◽  
Planetary Processes

Laser heating 40Ar/39Ar geochronology provides high analytical precision and accuracy, mum-scale spatial resolution, and statistically significant data sets for the study of geological and planetary processes. A newly commissioned 40Ar/39Ar laboratory at CPGeo/USP, São Paulo, Brazil, equips the Brazilian scientific community with a new powerful tool applicable to the study of geological and cosmochemical processes. Detailed information about laboratory layout, environmental conditions, and instrumentation provides the necessary parameters for the evaluation of the CPGeo/USP 40Ar/39Ar suitability to a diverse range of applications. Details about analytical procedures, including mineral separation, irradiation at the IPEN/CNEN reactor at USP, and mass spectrometric analysis enable potential researchers to design the necessary sampling and sample preparation program suitable to the objectives of their study. Finally, the results of calibration tests using Ca and K salts and glasses, international mineral standards, and in-house mineral standards show that the accuracy and precision obtained at the 40Ar/39Ar laboratory at CPGeo/USP are comparable to results obtained in the most respected laboratories internationally. The extensive calibration and standardization procedures undertaken ensure that the results of analytical studies carried out in our laboratories will gain immediate international credibility, enabling Brazilian students and scientists to conduct forefront research in earth and planetary sciences.

Accuracy and precision of the three-dimensional assessment of the facial surface using a 3-D laser scanner

2006 ◽  
Vol 25 (6) ◽  
pp. 742-754 ◽  
Author(s):  
L. Kovacs ◽  
A. Zimmermann ◽  
G. Brockmann ◽  
H. Baurecht ◽  
K. Schwenzer-Zimmerer ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Laser Scanner ◽  
Accuracy And Precision ◽  
Dimensional Assessment

Conversion of a Telecommunications Antenna into a Radio Telescope: Laser Scanner Measurements of Optics and Dish Surface Quality of a Cassegrain Antenna

2019 ◽  
Vol 08 (03) ◽  
pp. 1950010
Author(s):  
Asif Rasha ◽  
Tim Natusch ◽  
Christophe Granet ◽  
Sergei Gulyaev
Keyword(s):  
Surface Quality ◽  
Radio Telescope ◽  
Surface Deformation ◽  
Elevation Angle ◽  
Laser Scanner ◽  
Length Variation ◽  
Cassegrain Antenna ◽  
Telescope Optics

A number of countries have identified redundant large telecommunications antennas (TA) and indicated their intention to convert them into radio telescopes (RT). As the efficiency of a parabolic dish radio telescope depends on its surface quality and optical alignment, a careful assessment of these properties should be undertaken before conversion. Here, as a case study, we describe a laser scanning (LS) procedure we developed and used for the Warkworth 30[Formula: see text]m Cassegrain antenna. To investigate gravity-induced mechanical deformation of the antenna surfaces and structure, we conducted measurements at elevation angles ranging from 6 to 90 degrees. The ability of a laser scanner to survey its nominal [Formula: see text] steradian surroundings allows for simultaneous study of the main and subreflectors, readily permitting a dynamic investigation of variation of the telescope optics as elevation changes occur. In particular, the method we present here allows determination of the surface quality of both main and subreflectors, the displacement between centers of the reflectors, their relative rotations and focal length variation as a function of elevation angle. We discuss details of settings, measurements, data processing and analysis focusing on possible difficulties and pitfalls. In our case study, no significant elevation-dependent surface deformation of the reflectors was observed, with the overall standard deviation of the postfit residuals varying between 1.0 and 1.7[Formula: see text]mm as elevation angle changes from 90∘ to 6∘, respectively. We, therefore, conclude that in our case both the main reflector and the subreflector, as well as the telescope optics, remain unaffected by gravitational deformation within the accuracy of the measurements, a conclusion that can possibly be extended to the similar class of TA currently considered for conversion.

scholarly journals A NanoSIMS 50 L Investigation into Improving the Precision and Accuracy of the 235U/238U Ratio Determination by Using the Molecular 235U16O and 238U16O Secondary Ions

Minerals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 307 ◽  
Author(s):  
N. Zirakparvar ◽  
Cole Hexel ◽  
Andrew Miskowiec ◽  
Julie Smith ◽  
Michael Ambrogio ◽  
...  
Keyword(s):  
Reference Materials ◽  
The Other ◽  
Primary Beam ◽  
Uranium Compounds ◽  
Accuracy And Precision ◽  
Secondary Ions ◽  
Precision And Accuracy ◽  
Improved Accuracy ◽  
Secondary Ion ◽  
238U Ratio

A NanoSIMS 50 L was used to study the relationship between the 235U/238U atomic and 235U16O/238U16O molecular uranium isotope ratios determined from a variety of uranium compounds (UO2, UO2F2, UO3, UO2(NO3)2·6(H2O), and UF4) and silicates (NIST-610 glass and the Plesovice zircon reference materials, both containing µg/g uranium). Because there is typically a greater abundance of 235U16O+ and 238U16O+ molecular secondary ions than 235U+ and 238U+ atomic ions when uranium-bearing materials are sputtered with an oxygen primary ion beam, the goal was to understand whether use of 235U16O/238U16O has the potential for improved accuracy and precision when compared to the 235U/238U ratio. The UO2 and silicate reference materials showed the greatest potential for improved accuracy and precision through use of the 235U16O/238U16O ratio as compared to the 235U/238U ratio. For the UO2, which was investigated at a variety of primary beam currents, and the silicate reference materials, which were only investigated using a single primary beam current, this improvement was especially pronounced at low 235U+ count rates. In contrast, comparison of the 235U16O/238U16O ratio versus the 235U/238U ratio from the other uranium compounds clearly indicates that the 235U16O/238U16O ratio results in worse precision and accuracy. This behavior is based on the observation that the atomic (235U+ and 238U+) to molecular (235U16O+ and 238U16O+) secondary ion production rates remain internally consistent within the UO2 and silicate reference materials, whereas it is highly variable in the other uranium compounds. Efforts to understand the origin of this behavior suggest that irregular sample surface topography, and/or molecular interferences arising from the manner in which the UO2F2, UO3, UO2(NO3)2·6(H2O), and UF4 were prepared, may be a major contributing factor to the inconsistent relationship between the observed atomic and molecular secondary ion yields. Overall, the results suggest that for certain bulk compositions, use of the 235U16O/238U16O may be a viable approach to improving the precision and accuracy in situations where a relatively low 235U+ count rate is expected.

Aiming at self-calibration of terrestrial laser scanners using only one single object and one single scan

2014 ◽  
Vol 8 (4) ◽  
Author(s):  
Christoph Holst ◽  
Heiner Kuhlmann
Keyword(s):  
Stochastic Model ◽  
Functional Model ◽  
Laser Scanner ◽  
Systematic Errors ◽  
Sampling Point ◽  
Single Object ◽  
Self Calibration ◽  
Laser Scanners ◽  
Scanning Geometry ◽  
Calibration Parameters

AbstractWhen using terrestrial laser scanners for high quality analyses, calibrating the laser scanner is crucial due to unavoidable misconstruction of the instrument leading to systematic errors. Consequently, the development of calibration fields for laser scanner self-calibration is widespread in the literature. However, these calibration fields altogether suffer from the fact that the calibration parameters are estimated by analyzing the parameter differences of a limited number of substitute objects (targets or planes) scanned from different stations. This study investigates the potential of self-calibrating a laser scanner by scanning one single object with one single scan. This concept is new since it uses the deviation of each sampling point to the scanned object for calibration. Its applicability rests upon the integration of model knowledge that is used to parameterize the scanned object. Results show that this calibration approach is feasible leading to improved surface approximations. However, it makes great demands on the functional model of the calibration parameters, the stochastic model of the adjustment, the scanned object and the scanning geometry. Hence, to gain constant and physically interpretable calibration parameters, further improvement especially regarding functional and stochastic model is demanded.

scholarly journals ASSESSING THE ACCURACY AND PRECISION OF IMPERFECT POINT CLOUDS FOR 3D INDOOR MAPPING AND MODELING

2018 ◽  
Vol IV-4/W6 ◽  
pp. 3-10
Author(s):  
J. Chen ◽  
O. E. Mora ◽  
K. C. Clarke
Keyword(s):  
Low Cost ◽  
Random Noise ◽  
Three Dimensional ◽  
Laser Scanner ◽  
Point Clouds ◽  
Accuracy And Precision ◽  
Wide Range ◽  
Sharp Edges ◽  
The Cost ◽  
Indoor Spaces

<p><strong>Abstract.</strong> In recent years, growing public interest in three-dimensional technology has led to the emergence of affordable platforms that can capture 3D scenes for use in a wide range of consumer applications. These platforms are often widely available, inexpensive, and can potentially find dual use in taking measurements of indoor spaces for creating indoor maps. Their affordability, however, usually comes at the cost of reduced accuracy and precision, which becomes more apparent when these instruments are pushed to their limits to scan an entire room. The point cloud measurements they produce often exhibit systematic drift and random noise that can make performing comparisons with accurate data difficult, akin to trying to compare a fuzzy trapezoid to a perfect square with sharp edges. This paper outlines a process for assessing the accuracy and precision of these imperfect point clouds in the context of indoor mapping by integrating techniques such as the extended Gaussian image, iterative closest point registration, and histogram thresholding. A case study is provided at the end to demonstrate use of this process for evaluating the performance of the Scanse Sweep 3D, an ultra-low cost panoramic laser scanner.</p>

scholarly journals Precision and accuracy of four current 3D Printers to achieve models for Fixed Dental Prosthesis.

2020 ◽  
Vol 33 (1) ◽  
pp. 6-13
Author(s):  
Bianca Reis ◽  
Fernando Portella ◽  
Elken Rivaldo
Keyword(s):  
Dental Prosthesis ◽  
Fixed Dental Prosthesis ◽  
Dental Prostheses ◽  
Original Dataset ◽  
Accuracy And Precision ◽  
3D Printers ◽  
Fixed Dental Prostheses ◽  
Precision And Accuracy

The aim of this study was to compare the accuracy and precision of 3D printers used to obtain models of fixed dental prostheses. A fixed dental prosthesis preparation was scanned and reproduced by four 3D printers: RapidShape P40, Asiga MAX, Varseo, and Photon. The impressions were scanned again, and the dataset was compared to the original dataset. Mean discrepancies (µm) were 52.97±20.48 (RapidShape P40), 68.27±43.53 (Asiga MAX), 62.22±56.21 (Varseo), and 80.03±28.67 (Photon). There was no difference (p=0.314) in accuracy; however, the precision differed (p=0.015) among the 3D printers. The printers had distinct precision but did not differ in accuracy.

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