Geodetic Precision Research Articles

Developing a new interface for Qibla direction application based on MATLAB GUI

In this study, a MATLAB GUI-based interface has been developed that can be integrated with GNSS receivers. Through this interface developed for calculation and querying purposes, Qibla direction application with geodetic precision can be achieved using coordinate information of a corner of the mosque and its facade length, without the need for auxiliary geodetic measurement devices and computational burden. Furthermore, interface allows users to query the Qibla directions in mosques for inspection. It has been found that 2% of the mosques are outside the Qibla direction, 51% are outside the Miqat boundaries, and 8% are within the Haram boundaries.

Expedição científica ao alto curso do Rio Jaguaribe, Estado do Ceará: identificação da exata nascente do possivelmente maior rio efêmero do mundo

O Rio Jaguaribe é o maior rio do Ceará. Trata-se de um rio efêmero, possivelmente o maior “oued” do globo. Nos documentos oficiais, consta que suas nascentes se situam no Município de Tauá, na Serra da Joaninha, mas essa localização ainda é motivo de controvérsias. Uma expedição científica foi realizada ao alto curso do rio, fazendo uso de computadores, geomática, modelos digitais de elevação e drenagem, instrumentos de exploração e realização de cálculos com precisão topográfica e geodésica através de técnicas de sensores remotos, aerofotogrametria com drones e sistemas de posicionamentos globais por satélites do tipo GPS e GLOSNAS, e precisaram que a nascente principal (isto é, a de maior distância até a foz) se situa na verdade na divisa entre os muncípios de Tauá, Pedra Branca e Independência, na Serra das Pipocas, a partir da nascente do Riacho Carrapateiras. Essa descoberta geográfica deve a partir de agora ser homologada pelo Instituto Brasileiro de Geografia e Estatística – IBGE, Instituto de Pesquisas do Ceará – IPECE e publicações escolares.

INVESTIGATIONS ON THE GEOMETRIC QUALITY OF CAMERAS FOR UAV APPLICATIONS USING THE HIGH PRECISION UAV TEST FIELD ZOLLERN COLLIERY

Abstract. The geodetic-photogrammetric test field at the industrial monument Zollern colliery in Dortmund offers a scenario for carrying out geometric and radiometric tests of UAV systems. The foundation for this builds a geodetic precision network (position and height accuracy approx. 2 mm) with a total of 45 ground control points, distributed over an area of approx. 7 hectares. Within the scope of a campaign carried out in autumn 2017, various UAV sensor systems were tested under comparable conditions. Within this paper geometric investigations of two current DJI cameras, Zenmuse X4S (20 Mpix) and X5S (20.8 Mpix), as well as a Phase One IXU 1000 (100 Mpix) are presented. While the Zenmuse cameras reflect the current state of development of the manufacturer DJI, the medium format camera system from Phase One is primarily settled in the classic aerial segment. However, the desire for increased measurement accuracy (e. g. for engineering applications) also makes such a high-performance sensor interesting for UAV applications.In addition to the configuration of the test field, the system comparison requires identical parameters for flight planning, in particular image overlapping, a complete cross flight configuration at different flight altitudes and the definition of a uniform ground resolution (GSD = 14 mm).The investigations show clear differences in the achievable quality of the cameras. Though the high-priced Phase One system shows the best results, the most cost-effective system, the Zenmuse X4S, delivers only slightly worse results. In contrast, the Zenmuse X5S performs significantly worse than the other systems, mainly resulting from the mechanically unstable camera concept with interchangeable lenses. Finally, the comparison of the software products Pix4D Pix4Dmapper, Inpho UASMaster by Trimble and Agisoft PhotoScan partly shows significant differences in the results of image orientation. In particular in settings with sparse GCP usage the results vary considerably, indicating different strategies on how the residuals are distributed and the datum is defined, mostly Pix4Dmapper outperforms the others. In better GCP configurations there is no significant difference between Pix4mapper and Agisoft PhotoScan, while UASMaster does never deliver the best results.

Demonstration of a Broadband Very Long Baseline Interferometer System: A New Instrument for High‐Precision Space Geodesy

AbstractA prototype broadband geodetic very long baseline interferometry system has been implemented, and measurements of the baseline length over approximately two years, between December 2014 and January 2017, have been made in the process of exercising the system, developing operational procedures, and assessing geodetic precision for the new broadband observing concept. In addition to developing a broadband signal chain and installing the instrumentation on both a new 12‐m antenna at the Goddard Geophysical and Astrophysical Observatory and the 18‐m Westford antenna at the Massachusetts Institute of Technology Haystack Observatory, it was necessary to develop new correlation and analysis procedures to process the four‐band, dual‐linear‐polarization data. A geodetic analysis of the data from 19 sessions that were observed during this period yielded a weighted root‐mean‐square deviation of the baseline length residuals about the weighted mean of 1.6 mm. These results validate several of the expectations set forth for the vision of the next‐generation geodetic very long baseline interferometry system.

Estimation of the Length of Day (LOD) from DORIS observations

The paper is devoted to the estimation of the Length of the Day (LOD) from DORIS observations and summarizes the first successful experiment with LOD estimation at the level of geodetic precision. This result is confirmed by 9 years of DORIS data (2006.0–2015.0). The mean difference of the non smoothed LOD series with respect to the IERS C04 model reaches a value of tens µs and a standard deviation around 120 µs for the last years of the campaign 2012.0–2015.0. However, the mean difference with respect to the reference model varies over time, reaching negative values from −60 to −20 µs for the years 2006–2011 and positive values from 80 to 120 µs for the years 2012–2014. The time variable mean difference with respect to the changes in DORIS satellite constellation is discussed, as well as the possibility of the bias reduction applying the long-term averages of the cross-track harmonics or adjustment of the geopotential coefficient C20. Moreover, the possibility of LOD adjustment in the standard DORIS solution is discussed with focus on the station coordinates estimation. In addition, the power spectrum of the difference between estimated LOD and the reference model was performed, showing the domination of the annual signal. Also LOD estimated from single-satellite DORIS solutions was analyzed to identify satellite-specific issues. The paper includes a correlation analysis of the orbit parameters, Earth rotation parameters and the geopotential coefficient C20, based on covariance matrices from weekly solutions. High correlation around 0.96 was found for LOD and the sine amplitude of the cross-track harmonic empirical acceleration, which was also confirmed analytically.

Automated and dynamic scheduling for geodetic VLBI – A simulation study for AuScope and global networks

As we move into the next era of geodetic VLBI, the scheduling process is one focus for improvement in terms of increased flexibility and the ability to react with changing conditions. A range of simulations were conducted to ascertain the impact of scheduling on geodetic results such as Earth Orientation Parameters (EOPs) and station coordinates. The potential capabilities of new automated scheduling modes were also simulated, using the so-called ‘dynamic scheduling’ technique. The primary aim was to improve efficiency for both cost and time without losing geodetic precision, particularly to maximise the uses of the Australian AuScope VLBI array.We show that short breaks in observation will not significantly degrade the results of a typical 24 h experiment, whereas simply shortening observing time degrades precision exponentially. We also confirm the new automated, dynamic scheduling mode is capable of producing the same standard of result as a traditional schedule, with close to real-time flexibility. Further, it is possible to use the dynamic scheduler to augment the 3 station Australian AuScope array and thereby attain EOPs of the current global precision with only intermittent contribution from 2 additional stations. We thus confirm automated, dynamic scheduling bears great potential for flexibility and automation in line with aims for future continuous VLBI operations.

Towards terrestrial 3D data registration improved by parallel programming and evaluated with geodetic precision

Abstract In this paper a quantitative and qualitative evaluation of proposed ICP-based data registration algorithm, improved by parallel programming in CUDA (compute unified device architecture), is shown. The algorithm was tested on data collected with a 3D terrestrial laser scanner Z + F Imager 5010 mounted on the mobile platform PIONNER 3AT. Parallel implementation enables data registration on-line, even using a laptop with a standard hardware configuration (graphic card NVIDIA GeForce 6XX/7XX series). Robustness is assured by the use of CUDA-enhanced fast NNS (nearest neighbor search) applied for ICP (iterative closest point) with SVD (singular value decomposition) solver. The evaluation is based on the reference ground truth data registered with geodetic precision. The geodetic approach extends our previous work and gives an accurate benchmark for the algorithm. The data were collected in an urban area under a demolition scenario in a real environment. We compared four registration strategies concerning data preprocessing, such as subsampling and vegetation removal. The result is the analysis of measured performance and the accuracy of the geometric maps. The system provides accurate metric maps on-line and can be used in several applications such as mobile robotics for construction area modelling or spatial design support. It is a core component for our future work on mobile mapping systems.

New Test Facilities For GNSS Testing And Dynamic Calibration

Abstract With Galileo, the European GNSS (Global Navigation Satellite System) starting early services in 2015, open-area-testing of applications which use the new positioning system gets more and more important. This contribution gives an overview on existing test sites like railGATE, automotiveGATE and seaGATE, it highlights the latest addition for dynamic calibration with geodetic precision and finally describes the testing regime of the BONUS project ANCHOR, where multiple test sites are used for maximum benefit in a maritime application.

Long-Range Geo-Monitoring Using Image Assisted Total Stations

AbstractImage Assisted Total Stations (IATS) unify geodetic precision of total stations with areal coverage of images. The concept of using two IATS devices for high-resolution, long-range stereo survey of georisk areas has been investigated in the EU-FP7 project DE-MONTES (www.de-montes.eu). The paper presents the used methodology and compares the main features with other terrestrial geodetic geo-monitoring methods. The theoretically achievable accuracy of the measurement systemis derived and verified by ground truth data of a distant clay pit slope and simulated deformations. It is shown that the stereo IATS concept is able to obtain higher precision in the determination of 3D deformations than other systems of comparable sensor establishment effort.

Mars Orbiter Camera geodesy campaign

During the “geodesy campaign” in May and June 1999 the wide‐angle system of the Mars Global Surveyor Mars Orbiter Camera imaged the visible surface of Mars from latitudes 70°S to 90°N. Over 90% of this portion of the planet was covered at two viewing angles to obtain side‐looking stereo at a resolution of ∼250 m/pixel and convergence angles of 21°–27°. Continuous radiometric spacecraft tracking during this period provided precise orbit determination of spacecraft location. This data set will become the basis of a new image mosaic of Mars, with the potential to exceed the geodetic precision and image quality of those presently available.

Stochastic estimation of tropospheric path delays in global positioning system geodetic measurements

Water vapor radiometric (WVR) and surface meteorological (SM) measurements taken during three Global Positioning System (GPS) geodetic experiments are used to calculate process noise levels for random walk and first-order Gauss-Markov temporal models of tropospheric path delays. Entire wet and combined wet and dry zenith delays at each network site then are estimated simultaneously with the geodetic parameters without prior calibration. The path delays and corresponding baseline estimates are compared to those obtained with calibrated data and stochastic residual delays. In this manner, the marginal utility of a priori tropospheric calibration is assessed given the ability to estimate the path delays directly using only theGPS data. Estimation of total zenith path delays with appropriate random walk or Gauss-Markov models yields baseline repeatabilities of a few parts in 108. This level of geodetic precision, and accuracy as suggested by analyses on collocated baselines estimated independently by very long baseline interferometry, is comparable to or better than that obtained after path delay calibration usingWVR and/orSM measurements. Results suggest thatGPS data alone have sufficient strength to resolve centimeter-level zenith path delay fluctuations over periods of a few minutes.

Geodetic Precision in One Perspective

Aero-space vehicle guidance systems with accuracies superior to the capabilities of conventional geodetic measuring techniques, are generating requirements for geodetic positioning information. In addition, as measuring techniques are developed that approach the desired results, the improvement in precision of measurement becomes limited by uncertainties in knowledge of environmental factors affecting measurement accuracy, i.e., atmospheric refraction. Geodetic experiments with specially instrumented satellites have already returned several types of significant, useful data, that compare favorably with existing geodetic information in positional accuracy and offer advantages in range of measurement. Such experimentation shows that artificial satellites can contribute to improved geodetic precision by extending range and areal coverage of measurements, and by offering methods for improving knowledge of the fundamental constants used in geodetic measurements.

The Co-Ordination of the Trigonometrical Surveys of Queensland, New South Wales, Victoria and South Australia

Abstract The greater portion of this paper deals with an investigation into the records and values of the Victorian Geodetic Survey and the connection of that Survey with N.S.W. The problems and suggestions dealt therewith will apply equally to the other States. Every surveyor will recognise the necessity and advantages of co-ordinated surveys. A geodetic survey implies an extensive and precise co-ordination, unlimited by State boundaries, but extending throughout the length and breadth of a territory. Federal control of such a survey is obviously desirable, but unfortunately, that has not come to pass. The position to-day is that each State has carried out a certain amount of triangulation entirely independent of its neighbour or any other State. Different methods and standards of accuracy have been adopted, and whilst perhaps serving the purpose for which the survey was made, they do not permit of coordination to geodetic precision. This paper is intended to investigate the problem and to find out to wh...