Uniform Coordinate System Research Articles

Registration of terrestrial laser scanning data in forest areas using smartphone positioning and orientation data

ABSTRACT Terrestrial laser scanning (TLS) is an effective tool in forest inventory, but multiple scans are commonly required to cover the whole plot. Thus, it is necessary to register different scans into uniform coordinate system. Including auxiliary information to simplify registration is an effective idea, e.g., levelling scanner and measuring initial scanning direction, but requires additional survey equipment. In this letter, a registration method for forest TLS data is proposed, using smartphone to obtain auxiliary information. Scanner position and initial scanning direction are measured by smartphone for each scan and then used to calculate pair-wise coarse transformation parameters. In fine registration, we construct a series of transformation parameters based on coarse registration result and evaluate them by two-level objective functions, using stem positions as input. In this stage, stems far away from origin are excluded with filtering threshold set as the horizontal distance between scanner positions. The proposed method is validated on six scan pairs, with distance between scan positions ranging from 19 m to 40 m. The mean rotation, horizontal and vertical translation errors are 4.3′, 8.3 mm and 35 mm. Comparison with previous study shows auxiliary information from smartphone is beneficial for registration and filtering distant stems can improve registration accuracy.

Target Detection and Location by Fusing Delay-Doppler Maps

The use of delay-Doppler maps (DDMs) measured by Global Navigation Satellite System Reflectometry (GNSS-R) for target detection and location is a hot issue because of the potentially global coverage and short revisit periods of GNSS-R satellite missions. Existing researches have explored the detection of oil rigs, oil spills, sea ice, and other targets with spaceborne GNSS-R. However, these researches may not fully consider the advantages of multiple GNSS-R satellites, for example, Cyclone Global Navigation Satellite System (CYGNSS) which has eight satellites. Two problems of using multiple GNSS-R satellites for detection and location are how to estimate the sea clutter that is used to cancel the clutter in DDMs and how to remove location ambiguity caused by the transformation from the delay-Doppler (DD) domain to the spatial domain. In this article, an oil rig is taken as an example for detection and location with multiple GNSS-R satellites. To distinguish the oil rig from sea clutter, this article uses subspace projection to estimate the clutter and subtract the estimation from the DDMs. Moreover, after the clutter cancellation, this article projects the potential oil rig coordinates in the DD domain into a uniform coordinate system and removes the location ambiguity based on multisatellites fusion. The measured DDMs collected by CYGNSS are employed to conduct experiments to validate the feasibility of the proposed methods for detection and location with DDMs. By subtracting the estimated sea clutter from DDMs, the potential oil rig can be indicated in the DD domain. Two location experiments can calculate the unambiguous coordinate of the oil rig with a deviation less than 4 km.

Two- and three-dimensional deep human detection by generating orthographic top view image from dense point cloud

Human detection still suffers from occlusion, complex backgrounds, and scale-variant problems. Projecting three-dimensional (3D) points onto the ground to generate an orthographic top view (OTV) image for detection can effectively alleviate these problems. However, depth sensors may be placed arbitrarily, making it difficult to create OTV images by the dense point cloud converted from a depth image. We focus on the generation of OTV images and human detection via the constructed OTV image. First, we propose a ground plane extraction method that is well suitable for various camera positions and orientations in complex scenes. Next, points are converted to a uniform coordinate system by ground parameters and encoded to generate a three-channel OTV image. Then, the mainstream two-dimensional (2D) network is employed to detect the human directly on OTV images and further obtain the 3D bounding box by computing the mapping from the OTV image. Besides, we propose a semiautomated annotation method to solve the problem of few OTV image annotations. The proposed method is evaluated on the EPFL dataset, including two subsets, and achieves state-of-the-art performance compared with the existing approaches. Moreover, our 2D and 3D human detection method can run more than 26FPS on the CPU.

An Efficient Backprojection Algorithm Based on Wavenumber-Domain Spectral Splicing for Monostatic and Bistatic SAR Configurations

This paper introduces a fast backprojection synthetic aperture radar (SAR) imaging algorithm based on wavenumber-domain spectral splicing. The traditional fast backprojection (FBP) algorithm establishes the polar coordinate system with the center of the sub-aperture as the origin. Therefore, the coordinates of the image obtained from each sub-aperture are different. Sub-aperture images must be projected to a uniform coordinate system before they can be coherently superimposed to form the final image, which requires a large amount of calculation. In order to deal with this problem, this paper proposes a novel imaging method, which uses the same polar coordinate system for each sub-aperture. The sub-aperture images are then spliced in the wavenumber-domain, and directly added after upsampling. This method avoids the projection from each sub-aperture to the uniform coordinate system, thus improving the imaging accuracy and efficiency. At the same time, the algorithm is suitable for various configurations, and can achieve good imaging results for bistatic forward-looking SAR and high-speed mobile platform. Finally, simulations are presented to demonstrate the effectiveness of the algorithm.

Post-processing integration and semi-automated analysis of eye-tracking and motion-capture data obtained in immersive virtual reality environments to measure visuomotor integration.

Mobile eye-tracking and motion-capture techniques yield rich, precisely quantifiable data that can inform our understanding of the relationship between visual and motor processes during task performance. However, these systems are rarely used in combination, in part because of the significant time and human resources required for post-processing and analysis. Recent advances in computer vision have opened the door for more efficient processing and analysis solutions. We developed a post-processing pipeline to integrate mobile eye-tracking and full-body motion-capture data. These systems were used simultaneously to measure visuomotor integration in an immersive virtual environment. Our approach enables calculation of a 3D gaze vector that can be mapped to the participant's body position and objects in the virtual environment using a uniform coordinate system. This approach is generalizable to other configurations, and enables more efficient analysis of eye, head, and body movements together during visuomotor tasks administered in controlled, repeatable environments.

Enblending Mosaicked Remote Sensing Images With Spatiotemporal Fusion of Convolutional Neural Networks

Mosaicking of remote sensing images stitches images of different moments or sensors to produce a new image under a uniform geographic coordinate system. In a mosaicking process, the critical enblending operation is divided into color balance, seamline finder, and fusion of overlapping areas, which is still challenging to maintain color consistency and data fidelity. In this article, a new mosaicking framework using spatiotemporal fusion is proposed to solve the enblending issue. Two additional low-resolution reference images are introduced for each mosaicking image. With spatiotemporal fusion methods, all mosaicking images are reconstructed to a uniform time, then the combination of overlapping areas become easy. Furthermore, a new spatiotemporal fusion method is proposed by cascading enhanced deep neural networks to fuse images quickly and effectively. In the validation procedure, the proposed method is compared with eight color harmony methods or tools by mosaicking the red, green, and blue bands of Landsat-8 images with images from the moderate-resolution imaging spectroradiometer as the reference. The digital evaluations and visual comparisons demonstrate that the newly method outweighs majority methods regarding to the radiometric, structural, and spectral fidelity, which proves the feasibility of our new enblending method.

Displacement and deformation study of engineering structures with the use of modern laser technologies

Abstract Modern measuring technologies give the means to perform tasks previously impossible with conventional methods. Their main advantages include reduced time consumption and higher measurement precision. Contemporary displacement and deformation studies of engineering structures often involve application of laser technologies, which are characterised by high precision of measurements. This article presents an analysis of results obtained from measurements of changes in the geometry of an engineering structure in which two complementary measuring technologies were used, i.e. tachymetric measurement with a Leica TDRA6000 laser station and laser scanning with a 3D FARO Focus S150 scanner. The utilised laser station enabled determination of 3D displacements in the local control point network installed on the studied structure as well as transfer of point clouds obtained from laser scans into a uniform coordinate system. The hybrid technology employed and the measurement method used ensured that the accuracy of the determined displacements and deformations of the structural components of the structure was high. The described measurement and result processing technology makes it possible to comprehensively analyse the geometric performance of structures, which consequently leads to the development of more complete conclusions concerning prevention of adverse effects of displacements and deformations in engineering structures.

Опыт применения ГИС для оценки эколого-геоморфологических условий особо охраняемых природных территорий Прионежья (в пределах Вологодской области)

The assessment of ecological-geomorphological conditions of Verkhneandomsky (on the Upper Andoma river), “Atleka” and Andomskaya Gora (Andoma Mountain) protected areas was performed by Moscow State University and Moscow State University of Geodesy and Cartography researchers during 2002–2017. The aim of the study was to evaluate conditions for the development of exogenous relief-forming processes under the influence of natural factors using geoinformation systems (GIS). Topographic maps (scale 1:100 000) were vectorized and transformed to the uniform coordinate reference system (Gauss-Krueger projection, Pulkovo-42 datum). The GIS allows carrying out the ecological-geomorphological analysis of exogenous relief-forming processes of specially protected natural areas (PAs), relying on the grouped materials in the database, adding the parameters of the “erosion layer” and conducting their subsequent processing. Spatial analysis in GIS environment made it possible to identify similarities in karst processes and the difference in their intensity, expressed in the thickness and spatial distribution of the “erosion stratum” of the landscape reserves of the Verkhneandomsky and “Atleka”, which is defined by the relief of the karst-glacial-lake basin and the “karst” plateau, respectively. On the Andomskaya Gora natural monument, the suffusion-karst process and ravine dominate, which is caused by lithology (sand and sandstones) of rocks and significant relative height of the coastal ledge. Topographic, geological, geomorphological, and thematic information, as well as the boundaries and unique characteristics of the protected areas, allowed us to compile a series of derived maps reflecting the purpose of the research.

Coupling bending-torsional vibration model of gear - rotor

A rotor - bearing model of 5 degrees of freedom was established by finite element method, and a gear pair meshing model of 5 degrees of freedom was established by Newton’s second law. By introducing the azimuth, the gear rotor system could be designed with the gear pair arranging at will. Then through the transformation of coordinate system, the coordinate system of rotor-bearing model and gear pair model were unified, and the two were coupled together, and a complete gear-rotor model with uniform coordinate system was established.

Determining the Mechanisms that Influence the Surface Temperature of Urban Forest Canopies by Combining Remote Sensing Methods, Ground Observations, and Spatial Statistical Models

The spatiotemporal distribution pattern of the surface temperatures of urban forest canopies (STUFC) is influenced by many environmental factors, and the identification of interactions between these factors can improve simulations and predictions of spatial patterns of urban cool islands. This quantitative research uses an integrated method that combines remote sensing, ground surveys, and spatial statistical models to elucidate the mechanisms that influence the STUFC and considers the interaction of multiple environmental factors. This case study uses Jinjiang, China as a representative of a city experiencing rapid urbanization. We build up a multisource database (forest inventory, digital elevation models, population, and remote sensing imagery) on a uniform coordinate system to support research into the interactions that influence the STUFC. Landsat-5/8 Thermal Mapper images and meteorological data were used to retrieve the temporal and spatial distributions of land surface temperature. Ground observations, which included the forest management planning inventory and population density data, provided the factors that determine the STUFC spatial distribution on an urban scale. The use of a spatial statistical model (GeogDetector model) reveals the interaction mechanisms of STUFC. Although different environmental factors exert different influences on STUFC, in two periods with different hot spots and cold spots, the patch area and dominant tree species proved to be the main factors contributing to STUFC. The interaction between multiple environmental factors increased the STUFC, both linearly and nonlinearly. Strong interactions tended to occur between elevation and dominant species and were prevalent in either hot or cold spots in different years. In conclusion, the combining of multidisciplinary methods (e.g., remote sensing images, ground observations, and spatial statistical models) helps reveal the mechanism of STUFC on an urban scale.

A Hybrid Method of Determining Deformations of Engineering Structures with a Laser Station and a 3D Scanner

The article presents the technology and an analysis of results of engineering structure displacements and deformation measurements. Two measuring technologies using the TDRA65000 laser station from Leica and the FARO Focus M scanner were applied during the tests. Use of the laser station enabled us to define horizontal and vertical displacements of a control network established on the tested facility. Owing to this, it was also possible to transform scanner measuring stations into one integrated unit. The described measurement methodology ensures a high accuracy of scanner station fitting which translates directly into the accuracy of determination of deformations in structural components of a facility. Integration of methods applied in the tests makes it possible to monitor not only displacements of control network points but also the structure as a whole in a uniform coordinate system.

Front of the Werenskiold Glacier (Svalbard) – changes in years 1957–2013

Werenskiold Glacier in the Isle of Spitsbergen is one of the polygons on which evaluation of the rate of glacier recession is performed. Location of the glacier front is precisely presented in the specialist literature since the mid. 30. of 20th century. Article presents results of studies about changes in the position of Werenskiold Glacier based on selected archival data and own research conducted in 2012-2013. The initial location of the glacier front was described by the topographical map in the scale 1:5000 elaborated in the year 1961 on the basis of data from the years 1957-1959 by the Polish Army Topographic Service. Moreover, as comparative data on location of glacier front in the later years there were applied results of photogrammetrical images from the year 1973 and a orthophotomap from 1990. These data together with the author's GPS measurements were transformed into the uniform coordinate system. Thus, prepared data made it possible to evaluate the rate of recession of Werenskiold Glacier front in the three epochs from the years 1957-2013. It was found that during the 56 years the glacier front was moved by ca. 1200 m, which gives the mean recession value of 25 m/year as well as the mean yearly loss of the glacier surface of the order of 5 ha.

A regional method for craniofacial reconstruction based on coordinate adjustments and a new fusion strategy

Craniofacial reconstruction recreates a facial outlook from the cranium based on the relationship between the face and the skull to assist identification. But craniofacial structures are very complex, and this relationship is not the same in different craniofacial regions. Several regional methods have recently been proposed, these methods segmented the face and skull into regions, and the relationship of each region is then learned independently, after that, facial regions for a given skull are estimated and finally glued together to generate a face. Most of these regional methods use vertex coordinates to represent the regions, and they define a uniform coordinate system for all of the regions. Consequently, the inconsistence in the positions of regions between different individuals is not eliminated before learning the relationships between the face and skull regions, and this reduces the accuracy of the craniofacial reconstruction. In order to solve this problem, an improved regional method is proposed in this paper involving two types of coordinate adjustments. One is the global coordinate adjustment performed on the skulls and faces with the purpose to eliminate the inconsistence of position and pose of the heads; the other is the local coordinate adjustment performed on the skull and face regions with the purpose to eliminate the inconsistence of position of these regions. After these two coordinate adjustments, partial least squares regression (PLSR) is used to estimate the relationship between the face region and the skull region. In order to obtain a more accurate reconstruction, a new fusion strategy is also proposed in the paper to maintain the reconstructed feature regions when gluing the facial regions together. This is based on the observation that the feature regions usually have less reconstruction errors compared to rest of the face. The results demonstrate that the coordinate adjustments and the new fusion strategy can significantly improve the craniofacial reconstructions.

Methods of laser scanning point clouds integration in precise 3D building modelling

3D city models are built on the basis of photogrammetric data, especially laser scanning (LS) data. Due to the increasing levels of accuracy required of 3D city models, terrestrial and airborne laser scanning are the most frequently used technologies. The models are often fragmentary, based on only one type of geodata, e.g. aerial photography or airborne laser scanning (ALS) data. This paper presents various aspects of integrating data from different laser scanning technologies (terrestrial and airborne), which are at the moment considered to be the most detailed and accurate systems for the direct acquiring of 3D geodata. The main issue discussed in the paper is the integration of data in the form of point clouds acquiring from different laser scanning systems. Integration will be understood here as an appropriate processing of both sets of data for orientation into a uniform spatial coordinate system. Thus, the problem of extracting characteristic points common for both sets, in a way which will allow for obtaining a basis for building a complete and accurate 3D city model, will be fundamental. The main challenge when performing this task is to correctly and accurately specify the homologous point pairs used in 3D transformation when both data sets characterise different accuracy, density and content. In the present paper, manual (direct), semi-automatic (indirect determination of characteristic points by approximation) and automatic (3D model) methods for extracting characteristic points are presented, along with the results of an accuracy assessment. Furthermore different transformation methods (isometric, conformal and affine) are also verified, compared and analysed.

Smartphone‐based activity recognition independent of device orientation and placement

SummaryTraditional activity recognition methods based on accelerometers generally assume that the orientation and placement of sensing devices are fixed. However, the orientation and placement of smartphones, the most widely used sensing devices, usually cannot be controlled in daily lives. As a result, the activity recognition performance would be greatly affected. Aiming at this problem, this paper proposes a smartphone‐based activity recognition method, which is independent of device orientation and placement. First, the original 3D acceleration signals are mapped into a uniform reference coordinate system. Then, we apply multi‐dimensional motif discovery techniques for the smartphone‐based activity recognition problem. Experimental results show that our method can achieve better performance (with 85.2% precision and 82.9% recall) than other methods under the condition of unfixed orientation and placement. Copyright © 2015 John Wiley & Sons, Ltd.

Introducing WLab—Going from Wpt (Waypoint) to a uniform material color equivalency space

AbstractA set of invertible non‐linear transforms was derived that adjusts Wpt (Waypoint) coordinates (based on Wpt normalization) to and from a perceptually more uniform coordinate system (WLab or Waypoint‐Lab) than that provided by Wpt that allows for the advantageous features of Wpt to be directly applied to situations where other standard color spaces are typically used. The proposed transformations were found by optimizing for perceptual uniformity over both large and small color difference scales. The Munsell color order system was used as a representation for optimizing large‐scale perceptual uniformity. Correlations with Munsell value, chroma and hue along with comparisons with CIELAB and CAM02‐UCS were used to correct and assess overall large‐scale uniformity. The ΔE*94 color difference formula was used for optimization purposes for small‐scale uniformity. A STRESS analysis was applied to compare color differences based on Euclidean WLab distances with color differences based upon ΔE*ab, ΔE*94, ΔE00, DIN99o, CIECAM02, and CAM02‐UCS. It was found that WLab is a reasonably uniform material color equivalency space with small Euclidean WLab distances not being statistically different from ΔE*94, ΔE00, and Euclidean distances of DIN99o and CAM02‐UCS under reference observing conditions. © 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 550–563, 2015

Study on the Time-Grating Sensor Method of the Static Light Field Type Based on Timing-Driven

In order to time grating measurement principle application to the field of optical measurement, a uniform scan coordinate system by using photosensitive element of timing driven is presented to convert the displacement detection of the object into measured time difference. According to the conversion principle of relative motion coordinate systems of time grating, when view the photosensitive element of linear CCD as a uniform scanning coordinate system, view the spatial side by side and timing of mutually staggered on the two linear CCD as a stationary coordinate system, after measured the time difference variation of the output electric signal on the different CCD for the same object, size and direction of the relative displacement of the object would be made by multiplying time difference variation and scanning speed. With the calibration of the Renishaw laser interferometer for the developed linear CCD displacement sensor, the measuring errors are controlled within after error correction in the effective measuring range of 600.05mm. This realizes the idea of time measuring space in the field of optical.

Dynamic fisheye grids for binary black hole simulations

We present a new warped gridding scheme adapted to simulating gas dynamics in binary black hole spacetimes. The grid concentrates grid points in the vicinity of each black hole to resolve the smaller scale structures there, and rarefies grid points away from each black hole to keep the overall problem size at a practical level. In this respect, our system can be thought of as a ‘double’ version of the fisheye coordinate system, used before in numerical relativity codes for evolving binary black holes. The gridding scheme is constructed as a mapping between a uniform coordinate system—in which the equations of motion are solved—to the distorted system representing the spatial locations of our grid points. Since we are motivated to eventually use this system for circumbinary disc calculations, we demonstrate how the distorted system can be constructed to asymptote to the typical spherical polar coordinate system, amenable to efficiently simulating orbiting gas flows about central objects with little numerical diffusion. We discuss its implementation in the Harm3d code, tailored to evolve the magnetohydrodynamics equations in curved spacetimes. We evaluate the performance of the system’s implementation in Harm3d with a series of tests, such as the advected magnetic field loop test, magnetized Bondi accretion, and evolutions of hydrodynamic discs about a single black hole and about a binary black hole. Like we have done with Harm3d, this gridding scheme can be implemented in other unigrid codes as a (possibly) simpler alternative to adaptive mesh refinement.

Evolution of a stratified rotating shear layer with horizontal shear. Part 2. Nonlinear evolution

AbstractDirect numerical simulation is used to investigate the nonlinear evolution of a horizontally oriented mixing layer with uniform stable stratification and coordinate system rotation about the vertical axis. The important dimensional parameters governing inviscid dynamics are maximum shear $S(t)$, buoyancy frequency $N$, angular velocity of rotation $\Omega $ and characteristic shear thickness $L(t)$. The effect of rotation rate, $\Omega $, on the development of fluctuations in the shear layer is systematically studied in a regime of strong stratification. An instability mechanism, qualitatively distinct from the inertial instability, is found to deform columnar vortex cores in vertical planes for a strongly stratified rotating mixing layer. This mechanism emerges when centreline absolute vertical vorticity, $\langle {\omega }_{3} \rangle (t)+ 2\Omega $, is nearly zero as predicted by the linear stability analysis in Part 1 (J. Fluid. Mech., vol. 703, 2012, pp. 29–48). When the initial rotation rate is moderately anticyclonic, strong destabilization and a cascade to small scales is observed, consistent with prior studies involving horizontally sheared flow in the presence of rotation. Examination of enstrophy budgets in cases which are initially inertially unstable reveal the importance of baroclinic torque in maintaining lateral enstrophy fluctuations substantially beyond the time when the flow becomes inertially stable. The cyclonic stratified cases show weak nonlinearity in vortex dynamics. At high Reynolds number, despite the strong stratification, the flow exhibits three-dimensional, nonlinear dynamics and significant vertical mixing except for cases where the rotation is stabilizing.

LASER PROJECTION SYSTEM TO LOCALIZE ACUPOINTS ON FACE USING 3D HEAD MODEL

Clinical studies of acupuncture and moxibustion often are disapproved by international academic circles due to research methods and randomized controlled trials (RCT). Accurately localizing acupoints is a key issue in traditional Chinese medicine (TCM) therapy research. The objective of this study was to systematically propose an effective method to localize the acupoints on the head accurately and to track the points automatically with the movement of the body within a defined range using a laser projection system that comprises laser pointers, a control system, charge-coupled device (CCD) cameras, and a computer. A 3D head model, on which all acupoints were clearly marked and the coordinates of the points were extracted, was constructed previously using point clouds by a 3D scanner based on structured light. Then, a uniform coordinate system was established, in which correlations of model, CCD and body were described. Under signals from the point of the model, the beam emitted from each laser pointer was individually guided towards the head, pointing at the corresponding site on the head. The spot was captured by CCD to identify the localization of the acupoint. To test the validity of the proposed technique, the experiments were carried out. The experimental results show that the central points of the spots can be nearly in coincidence with the points localized directly in an experienced TCM expert, and the errors are within 3.1 mm. The results indicate also that the localization accuracy and the repeatability of acupoints are high disregarding the movement of the head. The work lays a research foundation for RCT in clinical studies of acupuncture and moxibustion.