Precise Geodesy Research Articles

MATERIALIZING THE LANDSCAPE: DRONES, GEODESY, AND 3D PRINTERS IN A VIABLE AND ECONOMIC SOLUTION FOR 3D MODELING: DRONES, GEODESY, AND 3D PRINTERS IN A VIABLE AND ECONOMIC SOLUTION FOR 3D MODELING

In recent years, environmental modeling has become increasingly crucial for understanding and mitigating the impacts of human activities on the environment. However, traditional methods for environmental mapping, primarily those of physical understanding, face challenges related to accuracy, time, and cost. In this sense, this work aimed to evaluate the technical feasibility of altimetric mapping and 3D model construction using drones, precision geodesy, and 3D printing as an extremely effective and low-cost alternative for environmental modeling. The study focused spatially on the boundaries of the IFRN/Campus Macau terrain. The study was conducted in five stages: I) Literature review; II) Geodetic survey (GNSS); III) Aerophotogrammetric survey; IV) Processing of geodetic and aerophotogrammetric data; and V) 3D printing. A protocol was obtained for the elaboration with high vertical and horizontal accuracy of the Digital Surface Model (DSM), orthomosaic, and 3D model (virtual and physical) of the mapped environment. Regarding the 3D model, its printing allowed for a perfect understanding of the geomorphology of the mapped environment and the existing physical structures. The applied technique could be useful in various areas, such as enhancing the planning stage in civil construction, architecture, and environmental studies. Also becoming a great ally in future geomorphological and tactile cartography studies.

Исследование возможностей использования постоянно действующих референцных станций в высокоточной геодезии и геодинамике

The author studies an opportunity of using GNSS observations on permanent geodetic reference points (base stations) for the high-precision geodesy and geodynamics purposes. It is assumed such GNSS observations may not completely meet the settled rules for GNSS observations in precise geodetic positioning. On the basis of processing real GNSS observations on the Moscow region’s reference stations in the course of seven years period an investigation of changing reference station positions was performed and typical variations and distortions that arise in positions of reference points during this long time period figured out. An analysis of possible reasons of occurring these effects and ways of eliminating them was carried out. Preliminary proposals how to filter out these adverse effects and bring the quality of GNSS processing results to the level required for the purposes of high precision geodesy and geodynamics were suggested.

Pre-mission InSights on the Interior of Mars

Abstract The Interior exploration using Seismic Investigations, Geodesy, and Heat Trans- port (InSight) Mission will focus on Mars’ interior structure and evolution. The basic structure of crust, mantle, and core form soon after accretion. Understanding the early differentiation process on Mars and how it relates to bulk composition is key to improving our understanding of this process on rocky bodies in our solar system, as well as in other solar systems. Current knowledge of differentiation derives largely from the layers observed via seismology on the Moon. However, the Moon’s much smaller diameter make it a poor analog with respect to interior pressure and phase changes. In this paper we review the current knowledge of the thickness of the crust, the diameter and state of the core, seismic attenuation, heat flow, and interior composition. InSight will conduct the first seismic and heat flow measurements of Mars, as well as more precise geodesy. These data reduce uncertainty in crustal thickness, core size and state, heat flow, seismic activity and meteorite impact rates by a factor of 3–10× relative to previous estimates. Based on modeling of seismic wave propagation, we can further constrain interior temperature, composition, and the location of phase changes. By combining heat flow and a well constrained value of crustal thickness, we can estimate the distribution of heat producing elements between the crust and mantle. All of these quantities are key inputs to models of interior convection and thermal evolution that predict the processes that control subsurface temperature, rates of volcanism, plume distribution and stability, and convective state. Collectively these factors offer strong controls on the overall evolution of the geology and habitability of Mars.

Influence of ocean tidal loading on InSAR offshore areas deformation monitoring

The ocean tide can cause the redistribution of the seawater mass, resulting in earth's surface deformation, namely ocean tidal loading (OTL). OTL vertical displacement may reach several centimeters, especially in coastal areas, so its effect in the field of high precision geodesy must be considered. This study concentrates on the influences of OTL on InSAR deformation measurements. We improve the osu.chinasea.2010 regional model and then compare the improved regional model with other regional models. It turns out that the improved regional model can achieve higher precision. Then we use it to replace the offshore part of the global model to generate the present model. We find that the displacement observed by the present model is 2–3 mm larger than that of other models on some sites. Finally, the present model is used to correct the deformation observed by InSAR of Shanghai and Los Angeles. A comparison between the displacements of IGS station with the corrected data shows that the OTL correction can improve the accuracy of InSAR deformation results by about 20%.

Geopotential measurements with synchronously linked optical lattice clocks

According to the Einstein's theory of relativity, the passage of time changes in a gravitational field. On earth, raising a clock by one centimetre increases its tick rate by 1.1 parts in 10$^{18}$, enabling optical clocks to perform precision geodesy. Here, we demonstrate geopotentiometry by determining the height difference of master and slave clocks separated by 15 km with uncertainty of 5 cm. The subharmonic of the master clock is delivered through a telecom fibre to phase-lock and synchronously interrogate the slave clock. This protocol rejects laser noise in the comparison of two clocks, which improves the stability of measuring the gravitational red shift. Such phase-coherently operated clocks facilitate proposals for linking clocks and interferometers. Over half a year, 11 measurements determine the fractional frequency difference between the two clocks to be $1,652.9(5.9)\times 10^{-18}$, or a height difference of 1,516(5) cm, consistent with an independent measurement by levelling and gravimetry. Our system is as a building block of an internet of clocks, consisting of a master and a number of slave clocks, which will provide "quantum benchmarks" that are height references with dynamic response.

Comparison of the frequency estimation of the DORIS/Jason2 oscillator thanks to the onboard DIODE and Time Transfer by Laser Link experiment

The main applications for DORIS are precise orbit determination, and precise Geodesy. Onboard Jason-2 for instance, the DORIS tracking component is the French contribution to the precise orbit determination capability, a key capability for altimetry product scientific result accuracy. T2L2 is a time transfer technique based on the propagation of light pulses for synchronization between two clocks. Hosting T2L2 on-board Jason-2 was to allow for very fine DORIS USO (Ultra-Stable Oscillator) frequency monitoring, and for this purpose T2L2 was connected to the DORIS USO. Thanks to the continuous tracking of T2L2/Jason-2 by the Laser Ranging network it is possible to monitor the USO for several days, weeks, and even much longer, and thus to also compare with the DIODE (the DORIS on-board orbit determination software) frequency bias estimates. The DORIS USO frequency biases estimate comparison between two independent systems, T2L2 and DIODE, can be of benefit to both, allowing the accuracies of both systems to be better understood, and for improvements to be made to both systems. Such comparison is the central topic of the present paper. T2L2 monitors the DORIS on-board USO frequency with an accuracy of much better than 10−12 which is the specification for the Doppler instrumentation.The paper investigates the limits of the DORIS-DIODE frequency bias estimates using T2L2, showing that USO frequency compliance accuracy of 10−12 has been reached.

A data archive for storing precision measurements

Precision measurements are essential to our understanding of the fundamental laws and symmetries of nature.Traditionally, fundamental symmetry tests focused on effects that are either time independent or subject to periodic modulation due to Earth’s rotation about its axis or its revolution around the Sun. In recent years, however, attention has been drawn to time-varying effects, starting with the searches for a possible temporal variation of fundamental “constants.” Even more recently, researchers are looking for transient effects11. S. Pustelny et al., Ann. Phys. 525, 659 (2013); https://doi.org/10.1002/andp.201300061 A. Derevianko, M. Pospelov, Nat. Phys. 10, 933 (2014). https://doi.org/10.1038/nphys3137 and oscillating effects22. P. W. Graham, S. Rajendran, Phys. Rev. D 88, 035023 (2013); https://doi.org/10.1103/PhysRevD.88.035023 B. M. Roberts et al., Phys. Rev. D 90, 096005 (2014). https://doi.org/10.1103/PhysRevD.90.096005 due to ultralight bosonic particles that could be components of dark matter or dark energy.To search for nonuniform dark energy or dark matter, researchers have proposed networks of atomic magnetometers and clocks.11. S. Pustelny et al., Ann. Phys. 525, 659 (2013); https://doi.org/10.1002/andp.201300061 A. Derevianko, M. Pospelov, Nat. Phys. 10, 933 (2014). https://doi.org/10.1038/nphys3137 The readings of remotely located network sensors are synchronized—for example, using the timing provided by GPS—and analyzed for specific transient features. Also being discussed are hybrid networks consisting of different types of sensors that would be sensitive to different possible interactions with the dark sector (see http://www.nature.com/nphys/journal/v10/n12/extref/nphys3137-s1.pdf).A compelling example of time-stamped and stored datasets is the orbit and clock estimates of the Global Navigation Satellite Systems (GNSS) available through the International GNSS Service (http://igscb.jpl.nasa.gov). This service is the backbone of modern precision geodesy. The available multiyear archival data can be used to search for transient variations of fundamental constants associated with the galactic motion through the dark-matter halo (see http://www.dereviankogroup.com/gps-dm/).The field of precision measurement appears to be undergoing a paradigm shift, with new theoretical and experimental ideas sprouting almost daily. For instance, reanalysis of data from using atomic dysprosium to look for the variation of the fine-structure constant and to test Lorentz invariance has set new limits on the scalar dark matter.33. K. V. Tilburg et al., Phys. Rev. Lett. 115, 011802 (2015). https://doi.org/10.1103/PhysRevLett.115.011802,44. Y. V. Stadnik, V. V. Flambaum, arXiv:1504.01798. That has been made possible by the existence of well-documented, accessible data sets stored electronically.An example of a new experimental idea is using precise beam-position monitors in particle accelerators to test for specific types of Lorentz-invariance violations.55. B. Wojtsekhowski, Europhys. Lett. 108, 31001 (2014). https://doi.org/10.1209/0295-5075/108/31001Inspired by all those exciting developments, we propose that data streams from any ongoing precision measurements be time-stamped and stored for possible future analysis. We are convinced that the cost of data storage and GPS timing is relatively small and that the data storage will be straightforward to implement technically, though, of course, the price and complexity crucially depend on the precision of the time stamp and the data rate. Conversely, failing to time-stamp and store the data is likely to be an enormous waste. The search for transient effects of the dark sector is already a good motivation to create a data archive, and additional ideas of how to use such data are likely to emerge in the future.What information should be time-stamped and recorded as a raw data stream? Data from optical and matter interferometers, experiments measuring parity violation and looking for permanent electric dipole moments, precision-measurement ion traps, all precision experiments with antimatter, and, by default, anything measured precisely.We live in the age of Google and GPS; our thinking about experimental data should be keeping up with the times!REFERENCESSection:ChooseTop of pageREFERENCES <<CITING ARTICLES1. S. Pustelny et al., Ann. Phys. 525, 659 (2013); https://doi.org/10.1002/andp.201300061 , Google ScholarCrossrefA. Derevianko, M. Pospelov, Nat. Phys. 10, 933 (2014). https://doi.org/10.1038/nphys3137, , Google ScholarCrossref, ISI2. P. W. Graham, S. Rajendran, Phys. Rev. D 88, 035023 (2013); https://doi.org/10.1103/PhysRevD.88.035023 , Google ScholarCrossrefB. M. Roberts et al., Phys. Rev. D 90, 096005 (2014). https://doi.org/10.1103/PhysRevD.90.096005, , Google ScholarCrossref3. K. V. Tilburg et al., Phys. Rev. Lett. 115, 011802 (2015). https://doi.org/10.1103/PhysRevLett.115.011802, Google ScholarCrossref4. Y. V. Stadnik, V. V. Flambaum, arXiv:1504.01798. Google Scholar5. B. Wojtsekhowski, Europhys. Lett. 108, 31001 (2014). https://doi.org/10.1209/0295-5075/108/31001, Google ScholarCrossref© 2015 American Institute of Physics.

Use of the Long Baseline Array in Australia for Precise Geodesy and Absolute Astrometry

AbstractWe report the results of a successful 12-hour 22-GHz VLBI experiment using a heterogeneous network that includes radio telescopes of the Long Baseline Array (LBA) in Australia and several VLBI stations that regularly observe in geodetic VLBI campaigns. We have determined positions of three VLBI stations, atca-104, ceduna and mopra, with an accuracy of 4–30 mm using a novel technique of data analysis. These stations have never before participated in geodetic experiments. We observed 105 radio sources, and amongst them 5 objects which have not previously been observed with VLBI. We have determined positions of these new sources with the accuracy of 2–5 mas. We make the conclusion that the LBA network is capable of conducting absolute astrometry VLBI surveys with an accuracy better than 5 mas.

Kinematics of the Earth Continental Drift

The drift of regions in northeast Eurasia was studied using the precise satellite geodesy method (Global Positioning System (GPS)). Observational data were analyzed invoking the International Database. Despite the rather short observations (∼6 years), the drift directions of the basic Eurasia and Northern America regions were detected and the drift velocities were estimated. The results of the study are discussed in general terms of the deformation and fracture of solids.

GPS measurements from the Ladakh Himalaya, India: Preliminary tests of plate-like or continuous deformation in Tibet

Observations of relative motion in a geodetic network in Ladakh, India, and across southern Tibet indicate slow shear on the Karakorum fault, rapid east-west extension across the whole of southern Tibet, and constant arc-normal convergence between India and southern Tibet along the Himalayan arc. Measurements of ten campaign-style and six permanent sites with global positioning system (GPS) precise geodesy provide these bounds on the style and rates of the large-scale deformation in the Tibet-Himalaya region. Divergence between sites at Leh, Ladakh, India, and Shiquanhe, western Tibet, as well as slow relative motion among sites within the Ladakh network, limit right-lateral slip parallel to the Karakorum fault to only 3.4 ± 5 mm/yr. This low rate concurs with a recent estimate of 3–4 mm/yr for Late Holocene time, but disagrees with the much higher rate of 30–35 mm/yr that has been used to argue for plate-like behavior of the Tibetan Plateau. Convergence between Ladakh and the Indian subcontinent at 18.8 ± 3 mm/yr at 224° ± 17° (1σ) differs little from estimates of convergence across the central segment of the Himalaya. Finally, lengthening of the baseline between Leh, Ladakh, and Lhasa (in southeastern Tibet) at 17.8 ± 1 mm/yr or between Leh and Bayi (farther to the southeast) at 18 ± 3 mm/yr, is consistent with an extrapolation of rates of east-west extension of the Tibetan Plateau based both on shorter GPS baselines (e.g., Lhasa-Simikot) and on diverging slip vectors of earthquakes in the Himalaya. We interpret these results to indicate that Tibet behaves more like a fl uid than like a plate

Earthquake cycle dominates contemporary crustal deformation in Central and Southern Andes

With the advent of global positioning system (GPS) technology and its applications to high precision geodesy, earth scientists have gained an unprecedented opportunity to study the kinematics and dynamics of present-day deformation processes along plate boundary zones. However, until now our knowledge of the deformation processes associated with the Andean subduction along the western coast of South America has been limited. Here we present first estimates of present-day crustal deformation rates in the central and southern sections of the Andes, between latitudes 22°S and 42°S. We find that the deformation in the central section of our study area is dominated by the interseismic phase of an earthquake deformation cycle, caused by 100% coupling of the thrust interface between the subducting Nazca and the overriding South America plates. The estimated depth of coupling is not uniform along strike: north of 30°S it is ∼33 km deep, while south of 35°S it reaches 50 km depth. In addition, we observed postseismic relaxation effects in the northern part of our network in the area of the 1995 M w8.0 Antofagasta earthquake. South of 38°S, we detected a similar deformation pattern as in the Antofagasta area which we attribute to postseismic relaxation effects of the 1960 M w9.5 Valdivia earthquake.

GPS meteorology: validation and comparisons with ground-based microwave radiometer and mesoscale model for the Italian GPS permanent stations

Ground-based GPS meteorology has been developed during the last decade. Beside the GPS traditional application for precise geodesy, the GPS system has proved to be a powerful tool in atmospheric studies, such as climatology and meteorology. During 1999, at the Space Geodesy Center (CGS) of the Italian Space Agency (ASI) an operative and automatic system was developed in order to produce GPS tropospheric parameters on a daily basic for the Italian GPS permanent stations. In this work the operational processing of the GPS data is described. Moreover, the validation of the GPS tropospheric parameters through a comparison with other independent GPS solutions as well as independent techniques is presented. The GPS internal validation of zenith tropospheric delay (ZTD) shows a bias of 5 mm (absolute values) and a standard deviation ranging from 4 to 20 mm. For a few stations a comparison is performed between the GPS derived precipitable water vapor (PWV) and both the one computed using the MM5 and the one measured by the water vapor radiometer (WVR) and radiosondes (RAOB). The agreement between GPS and MM5 is within the range of 2–7 mm; for GPS, WVR and RAOB the standard deviation ranges from 0.85 to 1.62 mm.

An analysis of high-accuracy tropospheric delay mapping functions

The correction of the propagation delay due to the neutral atmosphere has been recognized as the major modeling error for most of the radiometric space techniques used in precise geodesy, affecting mainly the height component of position. For low elevation angles, many of the existing mapping functions produce large errors and are therefore not suitable for those applications demanding the highest precision.We have benchmarked five mapping functions acknowledged to be the most accurate of those currently available: those developed by the Harvard-Smithsonian Center for Astrophysics (CfA), Chalmers University of Technology (Ifadis), the Jet Propulsion Laboratory (Lanyi), the Massachusetts Institute of Technology (MTT), and Haystack Observatory (NMF) against ray traces of a one-year data set of radiosonde profiles from 50 stations. From a station-by-station analysis, none of the mapping functions revealed themselves to be superior for all elevation angles. For elevation angles above 15 degrees, Lanyi, MTT, and NMF yield identical mean biases and the best total error performances. At lower elevation angles, Ifadis and NMF are clearly superior. As regards the r.m.s. scatter about the mean, Ifadis performs the best for all elevation angles, followed closely by Lanyi.

The role of GPs in the WEGENER project

In recent years, the Global Positioning System (GPS) has become a major tool for high precision geodesy. The precision is now better than 1 ppb. In this paper, the importance of GPS for the WEGENER project is highlighted. First, an overview of the GPS system is presented including a description of the development of its capabilities. One of the most significant developments of the past few years has been the establishment of the International GPS Service for Geodynamics (IGS). Thanks to its standards and products, the state-of-the-art in high precision GPS has been advanced considerably. Therefore, a summary of the goals and principles of IGS is presented next. This is followed by a compilation of the major GPS projects in Europe and its surrounding areas, since 1988. Most of these are not related to the WEGENER project, but it shows how much work has already been done. It also indicates the possible future role of GPS in WEGENER. Since all these projects are usually quite independent, they might benefit from the existence of a consistent, dense, accurate regional reference frame. This is exemplified by the success of IGS, which is based on an expanding global network of continuously operating permanent GPS stations. It provides a stable global reference frame, which makes it feasible to combine the results from independent field campaigns. In certain regions of the world the coverage is not yet optimal, however, and it is planned to further densify the IGS network. Therefore, it might be interesting to establish a dense regional GPS network in the general research area of WEGENER, which extends from Greenland to mid-Asia. This idea is promoted in Section 5 of the paper, where it is proposed to create such a network under the name of WEGNET, for WEGENER GPS Network. It would seek to establish new sites where none exist yet and to include existing stations that may already have been established for other purposes. Apart from providing a regional densification of IGS and a reference frame for WEGENER, the network may also yield valuable contributions to the monitoring of tectonic motions in the area and for studies concerning ocean and atmospheric loading.

GPS data, acquisition, environmental effects

Precise geodesy with the Global Positioning System (GPS) emerged in the early 1990s from a decade‐long incubation to find vigorous application worldwide. Today we enjoy a full 24‐satellite constellation, a new generation of high‐precision receivers at about one‐third the 1991 cost, a growing permanent global network, and a vital International GPS Service to support GPS geodesy worldwide. In addition, dedicated regional GPS networks are springing up on every continent. The period has been marked less by conceptual advance than by disciplined application and refinement. Here we review the key developments in receivers and networks, and in understanding the environmental factors that limit GPS geodetic performance.

Ionospheric calibration of single frequency VLBI and GPS observations using dual GPS data

The ionospheric effect is one of the main sources of error in Very Long Baseline Interferometry (VLBI) and Global Positioning System (GPS) high precision geodesy. Although the use of two frequencies allows the estimation of this effect, in some cases dual observations are not possible due to the available equipment or the type of observation. This paper presents the ionospheric calibration of single frequency VLBI and GPS observations based on the ionospheric electron content estimated from dual frequency GPS data. The ionospheric delays obtained with this procedure and the VLBI baseline length results have been compared with those obtained with dual frequency data. For the European geodetic VLBI baselines, both solutions agree at the 3–5 parts in 10−9 level. The noise introduced by the GPS-based calibration is in the order of 3 cm for the VLBI observables and of 10 cm for the GPS observables.

Satellite laser ranging and precise geodesy.

Satellite laser ranging and precise geodesy.

Hydrostatic levels in precision geodesy and crustal deformation measurement

Previous attempts to apply the principles of hydrostatic leveling to precision geodesy have been limited by the uniformity of the fluid density attainable in field environments. This is largely due to the effects of temperature variations in the fluid tube. We have overcome this difficulty by using water maintained near its maximum density at 3.98°C inside a counterflow heat exchanger to limit the variations in density to less than 1 ppm. We have demonstrated the feasibility of this method with a 14‐m prototype level and have used a computer model of the system to demonstrate the theoretical performance of instruments up to 1 km long. It appears possible, for example, to construct a fluid tube 200 m long, 12.5 cm in diameter, and weighing 3.8 kg/m that would provide uniform density to &lt;1 ppm in field environments between −40° and 50°C. In our attempt to use the 14‐m prototype pressure‐transfer level we were unable to exploit the density stability that we had achieved due to inadequacies in available pressure gauges.

Ephemeris errors of GPS satellites

Ephemeris errors are supposed to be a major factor limiting the usefulness ofGPS in high precision geodesy. Considerations of orbital mechanics suggest that, regardless of their complexity, the uncertainties in the solar radiation pressure model, the gravity field model, and the estimated initial state, may have simple effects on the ephemeris. This possibility has been tested by fitting linear combinations of simple functions—chosen on theoretical grounds—to simulated errors of three-day ephemerides. With a set of five functions for the across-track component, six for the radial, and seven for the along-track, it has been possible to fit the position errors to better than 1% of theirr.m.s values, in all the caces studied. The simulations included —besides solar radiation pressure errors—gravity field model and initial state uncertainties, as well as an unknown constant force along the axis of the solar panels. The solar radiation force was calculated taking into account the shape, orientation, and physical properties (reflectivity and specularity) of the main parts of the spacecraft, under various conditions of illumination (continuous sunlight, eclipses, etc.).

Geodesy by very long base line interferometry

Important advances were made between 1971 and 1974 in the development of very long base line interferometry (VLBI) techniques for precision geodesy, including repeated determinations of the length of a transcontinental base line within 5 parts in 108, accurate measurements of polar motion and the variation of universal time, and the establishment of a catalog of extragalactic radio sources with positional uncertainties smaller than 0.1 arc sec.An introduction to VLBI and an account of its early development have been given by Cohen [1973]. Counselman [1973] has reviewed applications of VLBI to geodesy and astrometry prior to 1973, and recently, Moran [1975a] has described the geodetic and astrometric results which have been obtained by VLBI through June 1974. Moran's review is particularly timely because he discusses important unpublished data, preliminary results, and work now in progress or being planned by the major VLBI groups in the United States.