DOCSLIB.ORG

UCGE Reports Improving the Accuracy and Resolution of SINS/DGPS Airborne Gravimetry Alexander Mark Bruton

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
UCGE Reports Improving the Accuracy and Resolution of SINS/DGPS Airborne Gravimetry Alexander Mark Bruton 8&*(5HSRUWV 1XPEHU Department of Geomatics Engineering Improving the Accuracy and Resolution of SINS/DGPS Airborne Gravimetry (URL: http://www.geomatics.ucalgary.ca/GradTheses.html) by Alexander Mark Bruton December 2000 UNIVERSITY OF CALGARY Improving the Accuracy and Resolution of SINS/DGPS Airborne Gravimetry by Alexander Mark Bruton A THESIS SUBMITTED TO THE FACULTY OF GRADUATE STUDIES IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF GEOMATICS ENGINEERING CALGARY, ALBERTA December, 2000 © Alexander Mark Bruton 2000 Abstract This dissertation describes improvements made to a system for airborne mapping of the gravity field of the Earth. The research is carried out using an airborne gravity system that is based on a Strapdown Inertial Navigation System (SINS) and receivers of the Global Positioning System in differential mode (DGPS). The objective of the research is to optimize the performance of the system, especially for geodesy and geophysics. An introduction to the field of airborne gravimetry is given and the state of current research in the field is surveyed. Data from recent airborne gravity campaigns is used to provide a detailed analysis of the DGPS error budget for airborne positioning, providing a realistic evaluation of the accuracy of current kinematic carrier phase techniques. A fundamental consideration of the various processes of differentiation is given and particular differentiating filters are proposed for the determination of high precision velocity and acceleration. A detailed analysis is given in the frequency domain of the DGPS error budget for acceleration determination. This provides an understanding of the characteristics of each of the relevant error sources for spatial resolutions up to 500 m and forms the basis for a set of recommendations regarding acceleration determination for airborne gravimetry. The limitations of the SINS gravimeter that are imposed by the accelerometer biases are analyzed and quantified. A thorough analysis is provided of the dynamics experienced by survey aircraft. The high-frequency errors affecting airborne gravimetry are analyzed in detail and methods for reducing them are proposed and implemented with success. An improvement to the performance of the system for medium-resolution applications is achieved and it is demonstrated for the first time that the SINS/DGPS system can be used for high-resolution applications. Major results include a demonstrated accuracy of 1.5 mGal for a spatial resolution of 2.0 km and an accuracy of 2.5 mGal for a resolution of 1.4 km. Improvements to processing methods have yielded slightly better performance than the LaCoste and Romberg gravimeter on a common flight. A method for removing the effect of the Phugoid motion has been proposed and implemented with success. iii Acknowledgements Graduate studies has been a wonderful experience for me. It has allowed me to learn, to travel to faraway places like Greenland and Brazil, and perhaps most importantly, to make some lasting friendships. I would like to express appreciation for the support I have received over the last four years: • To Dr. Klaus-Peter Schwarz, thank you for the opportunity to work within such a world-class research group during my graduate studies. Your support, encouragement, trust and technical leadership have made it a truly enjoyable and invaluable experience. • To those organizations whose financial support has made my graduate studies possible, especially the Natural Sciences and Research Council (NSERC) of Canada, whose support has been fundamental. Thanks to the Government of Alberta for support in the form of an Alberta Government Graduate Scholarship, to the University of Calgary for support in the form of the Helmut Moritz Graduate Scholarship and to the Department of Geomatics Engineering for financial support on several occasions. Also, thanks go to those organizations that improved my graduate experience in the form of awards and travel grants. • To past and present members of our research group at the University of Calgary. To Dr. Ming Wei, thank you for your generosity and for the practical work that has created the framework upon which many students at the University of Calgary have built, myself included. Although there are many others, I would like especially to thank Jan Skaloud, Craig Glennie, Yecai Li, Mohamed Mostafa, Michael Kern, Kris Keller, Fadi Bayoud and Sandy Kennedy for their help and partnership on many occasions. Craig is also thanked for thoroughly testing the first version of GREATGUN in his thesis work. • To my unofficial examining committee: Michael Kern, Jason Innes and especially Len Bruton. The quality of this dissertation was greatly improved as a result of iv the discussions we had and as a result of your thoughtful criticism of the first draft. Your encouragement and the time you spent to help me is truly appreciated. • Thanks goes to the Geomatics for Informed Decisions (GEOIDE) Network Centre of Excellence for financing my position at the University of Calgary for the last year and a half and for the great environment for collaboration that they helped create. Also, other members of the Airborne Gravity for Exploration and Mapping Project are thanked for enriching my learning experience. • To Rene Forsberg of the Danish National Survey and Cadastre (KMS), for the invitation to participate in the workshop and field test in Greenland, in June 1998. Greenland was an unforgettable experience! • To Hugh Martell and Darren Cosandier of Waypoint Consulting Ltd., for the loan of GrafNav 6.02. It made data processing a pleasure. • To Keith Tennant, for your feedback and the useful discussions we had. • To Intermap Technologies Corporation for the loan of the Honeywell Laseref III on many occasions and for the flight services that were provided. • To Steve Ferguson for your hospitality and for always being willing to help. • To Sander Geophysics Ltd. for the flight services that were provided during the two testing periods that I joined them in Ottawa. • To Vladimir Argeseanu for providing the upward continued reference gravity field for the Kananaskis campaign. • To Paul Mrstik for his generosity and help. • To the members of my examining committee for their advice: J.M. Brozena, M.G. Sideris, M.E. Cannon and J.W. Haslett. • To the staff in the main office of Geomatics Engineering, especially Anne Gehring. Your help is appreciated. On a more personal note, I would like to express appreciation to my family and friends who have been so supportive over the last four years, especially: • To Mum, Dad, Michelle, Nicole and Adrian, thank you for your friendship and your support. • Finally, thanks to my best friend Krista for sharing and dreaming with me. v Dedication This work is dedicated to my parents who teach me every day by example. To Mum, whose arms are always open, making ours the luckiest family in the world, and to Dad, whose love for us is evident in everything that he does. Thank you for your support, your strength, your patience, your friendship and your love. vi Table of Contents Abstract.............................................................................................................................iii Acknowledgements...........................................................................................................iv Dedication .........................................................................................................................vi Table of Contents ............................................................................................................vii List of Figures...................................................................................................................xi Notation, Symbols and Acronyms ................................................................................xiii Notation xiii List of acronyms xv List of symbols xvi Introduction ....................................................................................................................... 1 PART 1: BACKGROUND AND JUSTIFICATION ..................................................... 3 1 Background and Research Objectives..................................................................... 4 1.1 Gravimetry, airborne gravimetry and the SINS gravimeter 5 1.2 Why are airborne gravity measurements needed? 9 1.3 Related research 13 1.4 Statement of the problem 21 1.4.1 Objectives...................................................................................................... 22 1.4.2 Assumptions.................................................................................................. 22 2 Airborne Gravimetry Using a SINS ...................................................................... 24 2.1 The measurement model of airborne gravimetry 24 2.2 The error model of airborne gravimetry 26 2.3 The estimation process, the observables and the measuring systems 27 2.3.1 The process of estimating the gravity disturbance........................................ 28 2.3.2 The SINS as a measuring system .................................................................. 30 2.3.3 The GPS as a measuring system ................................................................... 34 2.3.4 The effects of other sources of error on gravity disturbance estimation....... 37 vii 2.4 Contributions of this dissertation 37 PART 2: DGPS FOR AIRBORNE GRAVITY MAPPING........................................ 39 3 On the Positioning Accuracy of Kinematic Carrier
Load more

Recommended publications
  • Wireless Accelerometer - G-Force Max & Avg
    The Leader in Low-Cost, Remote Monitoring Solutions Wireless Accelerometer - G-Force Max & Avg General Description Monnit Sensor Core Specifications The RF Wireless Accelerometer is a digital, low power, • Wireless Range: 250 - 300 ft. (non line-of-sight / low profile, capacitive sensor that is able to measure indoors through walls, ceilings & floors) * acceleration on three axes. Four different • Communication: RF 900, 920, 868 and 433 MHz accelerometer types are available from Monnit. • Power: Replaceable batteries (optimized for long battery life - Line-power (AA version) and solar Free iMonnit basic online wireless (Industrial version) options available sensor monitoring and notification • Battery Life (at 1 hour heartbeat setting): ** system to configure sensors, view data AA battery > 4-8 years and set alerts via SMS text and email. Coin Cell > 2-3 years. Industrial > 4-8 years Principle of Operation * Actual range may vary depending on environment. ** Battery life is determined by sensor reporting Accelerometer samples at 800 Hz over a 10 second frequency and other variables. period, and reports the measured MAXIMUM value for each axis in g-force and the AVERAGE measured g-force on each axis over the same period, for all three axes. (Only available in the AA version.) This sensor reports in every 10 seconds with this data. Other sampling periods can be configured, down to one second and up to 10 minutes*. The data reported is useful for tracking periodic motion. Sensor data is displayed as max and average. Example: • Max X: 0.125 Max Y: 1.012 Max Z: 0.015 • Avg X: 0.110 Avg Y: 1.005 Avg Z: 0.007 * Customer cannot configure sampling period on their own.
    [Show full text]
  • Measurement of the Earth Tides with a MEMS Gravimeter
    1 Measurement of the Earth tides with a MEMS gravimeter ∗ y ∗ y ∗ ∗ ∗ 2 R. P. Middlemiss, A. Samarelli, D. J. Paul, J. Hough, S. Rowan and G. D. Hammond 3 The ability to measure tiny variations in the local gravitational acceleration allows { amongst 4 other applications { the detection of hidden hydrocarbon reserves, magma build-up before volcanic 5 eruptions, and subterranean tunnels. Several technologies are available that achieve the sensi- p 1 6 tivities required for such applications (tens of µGal= Hz): free-fall gravimeters , spring-based 2; 3 4 5 7 gravimeters , superconducting gravimeters , and atom interferometers . All of these devices can 6 8 observe the Earth Tides ; the elastic deformation of the Earth's crust as a result of tidal forces. 9 This is a universally predictable gravitational signal that requires both high sensitivity and high 10 stability over timescales of several days to measure. All present gravimeters, however, have limita- 11 tions of excessive cost (> $100 k) and high mass (>8 kg). We have built a microelectromechanical p 12 system (MEMS) gravimeter with a sensitivity of 40 µGal= Hz in a package size of only a few 13 cubic centimetres. We demonstrate the remarkable stability and sensitivity of our device with a 14 measurement of the Earth tides. Such a measurement has never been undertaken with a MEMS 15 device, and proves the long term stability of our instrument compared to any other MEMS device, 16 making it the first MEMS accelerometer to transition from seismometer to gravimeter. This heralds 17 a transformative step in MEMS accelerometer technology.
    [Show full text]
  • A GUIDE to USING FETS for SENSOR APPLICATIONS by Ron Quan
    Three Decades of Quality Through Innovation A GUIDE TO USING FETS FOR SENSOR APPLICATIONS By Ron Quan Linear Integrated Systems • 4042 Clipper Court • Fremont, CA 94538 • Tel: 510 490-9160 • Fax: 510 353-0261 • Email: [email protected] A GUIDE TO USING FETS FOR SENSOR APPLICATIONS many discrete FETs have input capacitances of less than 5 pF. Also, there are few low noise FET input op amps Linear Systems that have equivalent input noise voltages density of less provides a variety of FETs (Field Effect Transistors) than 4 nV/ 퐻푧. However, there are a number of suitable for use in low noise amplifier applications for discrete FETs rated at ≤ 2 nV/ 퐻푧 in terms of equivalent photo diodes, accelerometers, transducers, and other Input noise voltage density. types of sensors. For those op amps that are rated as low noise, normally In particular, low noise JFETs exhibit low input gate the input stages use bipolar transistors that generate currents that are desirable when working with high much greater noise currents at the input terminals than impedance devices at the input or with high value FETs. These noise currents flowing into high impedances feedback resistors (e.g., ≥1MΩ). Operational amplifiers form added (random) noise voltages that are often (op amps) with bipolar transistor input stages have much greater than the equivalent input noise. much higher input noise currents than FETs. One advantage of using discrete FETs is that an op amp In general, many op amps have a combination of higher that is not rated as low noise in terms of input current noise and input capacitance when compared to some can be converted into an amplifier with low input discrete FETs.
    [Show full text]
  • Preliminary Estimation and Validation of Polar Motion Excitation from Different Types of the GRACE and GRACE Follow-On Missions Data
    remote sensing Article Preliminary Estimation and Validation of Polar Motion Excitation from Different Types of the GRACE and GRACE Follow-On Missions Data Justyna Sliwi´ ´nska 1,* , Małgorzata Wi ´nska 2 and Jolanta Nastula 1 1 Space Research Centre, Polish Academy of Sciences, 00-716 Warsaw, Poland; [email protected] 2 Faculty of Civil Engineering, Warsaw University of Technology, 00-637 Warsaw, Poland; [email protected] * Correspondence: [email protected] Received: 18 September 2020; Accepted: 22 October 2020; Published: 23 October 2020 Abstract: The Gravity Recovery and Climate Experiment (GRACE) mission has provided global observations of temporal variations in the gravity field resulting from mass redistribution at the surface and within the Earth for the period 2002–2017. Although GRACE satellites are not able to realistically detect the second zonal parameter (DC20) of geopotential associated with the flattening of the Earth, they can accurately determine variations in degree-2 order-1 (DC21, DS21) coefficients that are proportional to variations in polar motion. Therefore, GRACE measurements are commonly exploited to interpret polar motion changes due to variations in the global mass redistribution, especially in the continental hydrosphere and cryosphere. Such impacts are usually examined by computing the so-called hydrological polar motion excitation (HAM) and cryospheric polar motion excitation (CAM), often analyzed together as HAM/CAM. The great success of the GRACE mission and the scientific robustness of its data contributed to the launch of its successor, GRACE Follow-On (GRACE-FO), which began in May 2018 and continues to the present. This study presents the first estimates of HAM/CAM computed from GRACE-FO data provided by three data centers: Center for Space Research (CSR), Jet Propulsion Laboratory (JPL), and GeoForschungsZentrum (GFZ).
    [Show full text]
  • Utilising Accelerometer and Gyroscope in Smartphone to Detect Incidents on a Test Track for Cars
    Utilising accelerometer and gyroscope in smartphone to detect incidents on a test track for cars Carl-Johan Holst Data- och systemvetenskap, kandidat 2017 Luleå tekniska universitet Institutionen för system- och rymdteknik LULEÅ UNIVERSITY OF TECHNOLOGY BACHELOR THESIS Utilising accelerometer and gyroscope in smartphone to detect incidents on a test track for cars Author: Examiner: Carl-Johan HOLST Patrik HOLMLUND [email protected] [email protected] Supervisor: Jörgen STENBERG-ÖFJÄLL [email protected] Computer and space technology Campus Skellefteå June 4, 2017 ii Abstract Utilising accelerometer and gyroscope in smartphone to detect incidents on a test track for cars Every smartphone today includes an accelerometer. An accelerometer works by de- tecting acceleration affecting the device, meaning it can be used to identify incidents such as collisions at a relatively high speed where large spikes of acceleration often occur. A gyroscope on the other hand is not as common as the accelerometer but it does exists in most newer phones. Gyroscopes can detect rotations around an arbitrary axis and as such can be used to detect critical rotations. This thesis work will present an algorithm for utilising the accelerometer and gy- roscope in a smartphone to detect incidents occurring on a test track for cars. Sammanfattning Utilising accelerometer and gyroscope in smartphone to detect incidents on a test track for cars Alla smarta telefoner innehåller idag en accelerometer. En accelerometer analyserar acceleration som påverkar enheten, vilket innebär att den kan användas för att de- tektera incidenter så som kollisioner vid relativt höga hastigheter där stora spikar av acceleration vanligtvis påträffas.
    [Show full text]
  • Detection of Caves by Gravimetry
    Detection of Caves by Gravimetry By HAnlUi'DO J. Cmco1) lVi/h plates 18 (1)-21 (4) Illtroduction A growing interest in locating caves - largely among non-speleolo- gists - has developed within the last decade, arising from industrial or military needs, such as: (1) analyzing subsUl'face characteristics for building sites or highway projects in karst areas; (2) locating shallow caves under airport runways constructed on karst terrain covered by a thin residual soil; and (3) finding strategic shelters of tactical significance. As a result, geologists and geophysicists have been experimenting with the possibility of applying standard geophysical methods toward void detection at shallow depths. Pioneering work along this line was accomplishecl by the U.S. Geological Survey illilitary Geology teams dUl'ing World War II on Okinawan airfields. Nicol (1951) reported that the residual soil covel' of these runways frequently indicated subsi- dence due to the collapse of the rooves of caves in an underlying coralline-limestone formation (partially detected by seismic methods). In spite of the wide application of geophysics to exploration, not much has been published regarding subsUl'face interpretation of ground conditions within the upper 50 feet of the earth's surface. Recently, however, Homberg (1962) and Colley (1962) did report some encoUl'ag- ing data using the gravity technique for void detection. This led to the present field study into the practical means of how this complex method can be simplified, and to a use-and-limitations appraisal of gravimetric techniques for speleologic research. Principles all(1 Correctiolls The fundamentals of gravimetry are based on the fact that natUl'al 01' artificial voids within the earth's sUl'face - which are filled with ail' 3 (negligible density) 01' water (density about 1 gmjcm ) - have a remark- able density contrast with the sUl'roun<ling rocks (density 2.0 to 1) 4609 Keswick Hoad, Baltimore 10, Maryland, U.S.A.
    [Show full text]
  • Airborne Geoid Determination
    LETTER Earth Planets Space, 52, 863–866, 2000 Airborne geoid determination R. Forsberg1, A. Olesen1, L. Bastos2, A. Gidskehaug3,U.Meyer4∗, and L. Timmen5 1KMS, Geodynamics Department, Rentemestervej 8, 2400 Copenhagen NV, Denmark 2Astronomical Observatory, University of Porto, Portugal 3Institute of Solid Earth Physics, University of Bergen, Norway 4Alfred Wegener Institute, Bremerhaven, Germany 5Geo Forschungs Zentrum, Potsdam, Germany (Received January 17, 2000; Revised August 18, 2000; Accepted August 18, 2000) Airborne geoid mapping techniques may provide the opportunity to improve the geoid over vast areas of the Earth, such as polar areas, tropical jungles and mountainous areas, and provide an accurate “seam-less” geoid model across most coastal regions. Determination of the geoid by airborne methods relies on the development of airborne gravimetry, which in turn is dependent on developments in kinematic GPS. Routine accuracy of airborne gravimetry are now at the 2 mGal level, which may translate into 5–10 cm geoid accuracy on regional scales. The error behaviour of airborne gravimetry is well-suited for geoid determination, with high-frequency survey and downward continuation noise being offset by the low-pass gravity to geoid filtering operation. In the paper the basic principles of airborne geoid determination are outlined, and examples of results of recent airborne gravity and geoid surveys in the North Sea and Greenland are given. 1. Introduction the sea-surface (H) by airborne altimetry. This allows— Precise geoid determination has in recent years been facil- in principle—the determination of the dynamic sea-surface itated through the progress in airborne gravimetry. The first topography (ζ) through the equation large-scale aerogravity experiment was the airborne gravity survey of Greenland 1991–92 (Brozena, 1991).
    [Show full text]
  • Basic Principles of Inertial Navigation
    Basic Principles of Inertial Navigation Seminar on inertial navigation systems Tampere University of Technology 1 The five basic forms of navigation • Pilotage, which essentially relies on recognizing landmarks to know where you are. It is older than human kind. • Dead reckoning, which relies on knowing where you started from plus some form of heading information and some estimate of speed. • Celestial navigation, using time and the angles between local vertical and known celestial objects (e.g., sun, moon, or stars). • Radio navigation, which relies on radio‐frequency sources with known locations (including GNSS satellites, LORAN‐C, Omega, Tacan, US Army Position Location and Reporting System…) • Inertial navigation, which relies on knowing your initial position, velocity, and attitude and thereafter measuring your attitude rates and accelerations. The operation of inertial navigation systems (INS) depends upon Newton’s laws of classical mechanics. It is the only form of navigation that does not rely on external references. • These forms of navigation can be used in combination as well. The subject of our seminar is the fifth form of navigation – inertial navigation. 2 A few definitions • Inertia is the property of bodies to maintain constant translational and rotational velocity, unless disturbed by forces or torques, respectively (Newton’s first law of motion). • An inertial reference frame is a coordinate frame in which Newton’s laws of motion are valid. Inertial reference frames are neither rotating nor accelerating. • Inertial sensors measure rotation rate and acceleration, both of which are vector‐ valued variables. • Gyroscopes are sensors for measuring rotation: rate gyroscopes measure rotation rate, and integrating gyroscopes (also called whole‐angle gyroscopes) measure rotation angle.
    [Show full text]
  • Full Auto-Calibration of a Smartphone on Board a Vehicle Using IMU and GPS Embedded Sensors
    Full auto-calibration of a smartphone on board a vehicle using IMU and GPS embedded sensors Javier Almaz´an, Luis M. Bergasa, J. Javier Yebes, Rafael Barea and Roberto Arroyo Abstract| Nowadays, smartphones are widely used Smartphones provide two kinds of measurements. The in the world, and generally, they are equipped with first ones are relative to the world, such as GPS and many sensors. In this paper we study how powerful magnetometers. The second ones are relative to the the low-cost embedded IMU and GPS could become for Intelligent Vehicles. The information given by device, such as accelerometers and gyroscopes. Knowing accelerometer and gyroscope is useful if the relations the relation between the smartphone reference system between the smartphone reference system, the vehicle and the world reference system is very important in order reference system and the world reference system are to reference the second kind of measurements globally [3]. known. Commonly, the magnetometer sensor is used In other words, working with this kind of measurements to determine the orientation of the smartphone, but its main drawback is the high influence of electro- involves knowing the pose of the smartphone in the magnetic interference. In view of this, we propose a world. novel automatic method to calibrate a smartphone Intelligent Vehicles can be helped by using in-vehicle on board a vehicle using its embedded IMU and smartphones to measure some driving indicators. On the GPS, based on longitudinal vehicle acceleration. To one hand, using smartphones requires no extra hardware the best of our knowledge, this is the first attempt to estimate the yaw angle of a smartphone relative to a mounted in the vehicle, offering cheap and standard vehicle in every case, even on non-zero slope roads.
    [Show full text]
  • Resolving Geophysical Signals by Terrestrial Gravimetry: a Time Domain Assessment of the Correction-Induced Uncertainty
    Originally published as: Mikolaj, M., Reich, M., Güntner, A. (2019): Resolving Geophysical Signals by Terrestrial Gravimetry: A Time Domain Assessment of the Correction-Induced Uncertainty. - Journal of Geophysical Research, 124, 2, pp. 2153—2165. DOI: http://doi.org/10.1029/2018JB016682 RESEARCH ARTICLE Resolving Geophysical Signals by Terrestrial Gravimetry: 10.1029/2018JB016682 A Time Domain Assessment of the Correction-Induced Key Points: Uncertainty • Global-scale uncertainty assessment of tidal, oceanic, large-scale 1 1 1,2 hydrological, and atmospheric M. Mikolaj , M. Reich , and A. Güntner corrections for terrestrial gravimetry • Resolving subtle gravity signals in the 1Section Hydrology, GFZ German Research Centre for Geosciences, Potsdam, Germany, 2Institute of Environmental order of few nanometers per square Science and Geography, University of Potsdam, Potsdam, Germany second is challenged by the statistical uncertainty of correction models • Uncertainty computed for selected periods varies significantly Abstract Terrestrial gravimetry is increasingly used to monitor mass transport processes in with latitude and altitude of the geophysics boosted by the ongoing technological development of instruments. Resolving a particular gravimeter phenomenon of interest, however, requires a set of gravity corrections of which the uncertainties have not been addressed up to now. In this study, we quantify the time domain uncertainty of tide, global Supporting Information: atmospheric, large-scale hydrological, and nontidal ocean loading corrections. The uncertainty is • Supporting Information S1 assessed by comparing the majority of available global models for a suite of sites worldwide. The average uncertainty expressed as root-mean-square error equals 5.1 nm/s2, discounting local hydrology or air Correspondence to: pressure. The correction-induced uncertainty of gravity changes over various time periods of interest M.
    [Show full text]
  • Macroscopic Superpositions and Gravimetry with Quantum Magnetomechanics Received: 07 July 2016 Mattias T
    www.nature.com/scientificreports OPEN Macroscopic superpositions and gravimetry with quantum magnetomechanics Received: 07 July 2016 Mattias T. Johnsson, Gavin K. Brennen & Jason Twamley Accepted: 24 October 2016 Precision measurements of gravity can provide tests of fundamental physics and are of broad Published: 21 November 2016 practical interest for metrology. We propose a scheme for absolute gravimetry using a quantum magnetomechanical system consisting of a magnetically trapped superconducting resonator whose motion is controlled and measured by a nearby RF-SQUID or flux qubit. By driving the mechanical massive resonator to be in a macroscopic superposition of two different heights our we predict that our interferometry protocol could, subject to systematic errors, achieve a gravimetric sensitivity of Δg/g ~ 2.2 × 10−10 Hz−1/2, with a spatial resolution of a few nanometres. This sensitivity and spatial resolution exceeds the precision of current state of the art atom-interferometric and corner-cube gravimeters by more than an order of magnitude, and unlike classical superconducting interferometers produces an absolute rather than relative measurement of gravity. In addition, our scheme takes measurements at ~10 kHz, a region where the ambient vibrational noise spectrum is heavily suppressed compared the ~10 Hz region relevant for current cold atom gravimeters. Gravimetry is the measurement of the local acceleration due to gravity on a test body. As gravity is an infinite range force that cannot be shielded against, it provides a useful probe for a variety of effects over a wide range of distances. Given a theory of gravity, gravimetry provides information about local mass distribution or, given a known, local mass distribution, it provides information that can be used test theories of gravity.
    [Show full text]
  • Pendulum MEMS Gravimeters for Semi-Absolute Gravimetry
    EGU2020-1244 https://doi.org/10.5194/egusphere-egu2020-1244 EGU General Assembly 2020 © Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License. Pendulum MEMS gravimeters for semi-absolute gravimetry Richard Middlemiss1, Giles Hammond2, Richard Walker2, and Abhinav Prasad2 1University of Glasgow, James Watt School of Engineering, Glasgow, United Kingdom of Great Britain and Northern Ireland ([email protected]) 2University of Glasgow, Institute for Gravitational Research, Glasgow, United Kingdom of Great Britain and Northern Ireland By measuring tiny variations in the Earth’s gravitational acceleration, g, one can infer density variations beneath the ground. Since magmatic systems contain rock of differing density, changes in gravity over time can tell us when/where magma is moving. Traditional gravity sensors (gravimeters) were costly and heavy, but with the advent of the technology used to make mobile phone accelerometers (MEMS – Microelectromechanical-systems), this is changing. At Glasgow University we have already developed the first MEMS gravity sensor and we are now working with several other European institutions to make a network of gravity sensors around Mt Etna – NEWTON-g. It will be the first multi-pixel gravity imager – enabling unprecedented resolution of Etna’s plumbing system. While this work is ongoing, a second generation of MEMS gravity sensor is now under development. The first-generation sensor comprises a mass on a spring, which moves in response to changing values of g. This, however, can only ever be used to measure changes in gravity, which means it can be difficult to tell the difference between a geophysical signal and instrumental drift.
    [Show full text]