GNSS Positioning and Applications Quiz
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Questions and Answers

What is a key advantage of static methods in positioning?

  • Speed in data collection
  • Cost-effectiveness compared to topographic methods (correct)
  • Lower precision compared to dynamic methods
  • Requiring continuous movement for accuracy

    • Which application is NOT typically associated with static positioning?

  • Tectonic Movement Monitoring
  • Deformation monitoring in dams and structures
  • Geodetic Control
  • Kinematic Positioning of moving objects (correct)

    • For a baseline length of 50-100 km, what is the minimum observation time required?

  • Minimum 3 hours
  • Minimum 2 hours (correct)
  • 2 hours
  • 1 hour

    • What happens if ambiguity is lost in kinematic positioning?

    <p>The process must be re-initialized.</p> Signup and view all the answers

    What is essential for sustaining accuracy in kinematic positioning?

    <p>Continuous ambiguity maintenance</p> Signup and view all the answers

    What is the primary focus area of the geostationary orbit (GEO) satellite described?

    <p>Asia</p> Signup and view all the answers

    How many satellites comprise the IRNSS/NAVIC system?

    <p>7</p> Signup and view all the answers

    Which GNSS system has the highest number of operational satellites listed?

    <p>BEIDOU</p> Signup and view all the answers

    What type of orbit do the four inclined GEO satellites of the IRNSS follow?

    <p>Figure-eight orbit</p> Signup and view all the answers

    Which of the following is primarily a Kinematic-RTK application?

    <p>Trajectory Determination</p> Signup and view all the answers

    Which of the following is NOT a source of error in GNSS accuracy?

    <p>Electronic delay</p> Signup and view all the answers

    What error arises when satellite clocks drift from the GNSS system's time?

    <p>Satellite clock error</p> Signup and view all the answers

    What is one of the main uses of GNSS methods?

    <p>Differential Positioning</p> Signup and view all the answers

    How many orbital planes are used by the NAVSTAR-GPS satellites?

    <p>6</p> Signup and view all the answers

    In which atmospheric layer is signal refraction more pronounced?

    <p>Troposphere</p> Signup and view all the answers

    How many frequencies does the IRNSS/NAVIC system use according to the operational status?

    <p>1</p> Signup and view all the answers

    Which GNSS system is particularly effective in polar regions?

    <p>GLONASS</p> Signup and view all the answers

    What is the orbital altitude of the GALILEO satellites?

    <p>23,222 km</p> Signup and view all the answers

    How many satellites does the BEIDOU navigation system consist of?

    <p>35</p> Signup and view all the answers

    Which of the following GNSS applications is specifically mentioned under GNSS applications?

    <p>Replanting</p> Signup and view all the answers

    What is the inclination angle of satellites in the GLONASS system?

    <p>64.8°</p> Signup and view all the answers

    What is the primary effect of multipath on GNSS signals?

    <p>It causes signal distortion and degrades navigation accuracy.</p> Signup and view all the answers

    Which factors can influence the accuracy of ephemeris data?

    <p>Gravity, solar radiation pressure, and atmospheric drag.</p> Signup and view all the answers

    How does GDOP affect positioning accuracy?

    <p>GDOP quantifies the geometric strength of satellite coverage.</p> Signup and view all the answers

    What is the purpose of Differential Positioning?

    <p>To enhance accuracy by using a fixed reference station.</p> Signup and view all the answers

    Which method is primarily used to enhance GNSS positioning accuracy through signal corrections from geostationary satellites?

    <p>Satellite-Based Augmentation Systems (SBAS)</p> Signup and view all the answers

    What does horizontal dilution of precision (HDOP) specifically impact?

    <p>Horizontal positioning accuracy.</p> Signup and view all the answers

    How does space weather, particularly solar activity, affect GNSS signals?

    <p>It decreases the density of the ionosphere, leading to increased refraction errors.</p> Signup and view all the answers

    What does improper antenna mounting primarily lead to?

    <p>Significant positioning errors.</p> Signup and view all the answers

    What is the primary purpose of the Global Navigation Satellite System (GNSS)?

    <p>To offer precise positioning and synchronization information globally</p> Signup and view all the answers

    How many satellites must a receiver communicate with to accurately determine its three-dimensional position?

    <p>At least three satellites</p> Signup and view all the answers

    What is the altitude range for Medium Earth Orbit (MEO) satellites?

    <p>From 19,180 to 28,000 km</p> Signup and view all the answers

    Which segment of GNSS is responsible for controlling and monitoring the satellites?

    <p>Control Segment</p> Signup and view all the answers

    What is essential for the accuracy of GNSS measurements?

    <p>The signal travel time from satellites</p> Signup and view all the answers

    How many satellites are required for three-dimensional positioning?

    <p>Three satellites</p> Signup and view all the answers

    Why do GNSS satellites need to be distributed in different orbital planes?

    <p>To ensure visibility from any location on Earth</p> Signup and view all the answers

    Which method relies on analyzing frequency shifts to determine distance?

    <p>The Doppler Effect</p> Signup and view all the answers

    What is the primary use of Low Earth Orbit (LEO) satellites?

    <p>Observation</p> Signup and view all the answers

    What mechanism do communication satellites utilize within the GNSS framework?

    <p>They enhance GNSS by retransmitting corrected information</p> Signup and view all the answers

    Which of the following accurately describes the function of the satellite's almanac?

    <p>Valid for about 6 months</p> Signup and view all the answers

    What function do spare satellites serve in the GNSS system?

    <p>They ensure global coverage and allow for speedy replacements</p> Signup and view all the answers

    What frequency does the L2 carrier wave transmit at?

    <p>1227.60 MHz</p> Signup and view all the answers

    When was the Global Positioning System (NAVSTAR - GPS) originally developed?

    <p>During the 1970s</p> Signup and view all the answers

    How is distance calculated using Code Measurement?

    <p>By measuring full and fractional wavelengths of the signal</p> Signup and view all the answers

    Which code modulates the L1 carrier at a frequency of 1.023 MHz?

    <p>C/A code</p> Signup and view all the answers

    Study Notes

    GNSS Systems (Global Navigation Satellite Systems)

    • GNSS emerged in the 1970s with the development of the NAVSTAR-GPS (US military application).
    • Civil use extended in the 1990s.
    • GNSS provide precise positioning and timing anywhere on Earth, economically.
    • They don't require visual line-of-sight between stations.
    • GNSS systems are constellations of satellites orbiting the Earth at various altitudes.
    • Signals from these satellites enable the calculation of a receptor's 3D position on earth.
      • Calculating 3D position involves measuring distance to at least three known satellite positions.
      • A fourth satellite is needed to calculate altitude.
    • Satellite's ephemeris are used to measure the distance between the receiver and satellites using signal travel time.
    • Accurate satellite clocks (timekeeping) are important for precise distance measurements.
    • GNSS systems are split into Space, Control, and User segments.

    Space Segment

    • Contains the navigation satellites.
    • Transmit signals on different frequencies.
    • Includes a constellation of satellites for communication and navigation.
    • A sufficient number of satellites are required to ensure global coverage.
    • Backup satellites are available to replace components or for additional coverage.
    • Satellites need to be distributed in multiple orbital planes.
    • A minimum of five visible satellites should always be present over any location.

    Control Segment

    • Monitors satellites' signals and orbital parameters.
    • Tracks the positions of satellites over time.
    • Transmits this information to a central station (CSOC, Colorado Springs, USA).
    • Uses the data to predict satellite orbits and clock corrections.
    • Uploads information about orbits and clock corrections to the satellites so receivers can use it to determine position.
      • Monitors satellite health and subsystems (solar panels, energy from batteries, propellers).
    • Updates navigation messages with ephemeris, almanac, and clock corrections to satellites.
    • Solves any issues with individual satellites.
      • Manages the availability and anti-spoofing of the signals.
      • Tracks each satellite's status passively.

    User Segment

    • Consists of GPS/GNSS receivers.
    • Includes military receivers, mobile phones, and vehicles.
    • Captures satellite signals and determines location, speed, or time.
    • Different types of receptors are possible (passive or active).

    Support Segment

    • Consists of ground stations.
    • Collect data on satellites' positions.
    • Corrects position inaccuracies.
    • Forms part of both the control and user segments.

    Geostationary Earth Orbit (GEO) Satellites

    • Orbit the Earth at about 35,848 km.
    • Appear stationary from a ground-based perspective. They orbit at a speed identical to the Earth's rotation, so their position relative to the Earth remains constant.
    • Used in communication and some augmentation systems (SBAS).

    Medium Earth Orbit (ΜΕΟ) Satellites

    • Orbit at altitudes between 19,180 and 28,000 km.
    • Used in positioning systems.

    Low Earth Orbit (LEO) Satellites

    • Orbit at roughly 800 km.
    • Primarily used for observation.

    Calculation of Position

    • Satellites' positions and clock data are necessary.
    • Receivers measure signals’ travel times.
    • Calculating distances from the receiver to several satellites yields the receiver’s position and time.

    Signal Characteristics

    • Satellites constantly transmit on two carrier waves (L1 and L2).
    • Wave frequencies are based on precisely timed atomic clocks.
    • Each carrier wave is modulated by two codes: C/A and P-code.
      • C/A code is for general use, offering lower precision.
      • P-code is for secure applications, delivering higher precision.

    Errors in GNSS

    • Errors come from both systematic and random sources.
    • Satellite clocks and receiver clocks introduce errors.
    • Ionospheric and tropospheric delays cause further inaccuracies.

    GNSS Constellations Overview

    • GPS: US-based, 24 satellites in six planes.
    • GLONASS: Russian, 24 satellites in three planes.
    • BeiDou: Chinese, 35 satellites in 3+ orbits.
    • QZSS: Japanese, primarily for the Asian region and has three GEO satellites and one in geosynchronous orbit
    • Galileo: European, 26 satellites in three planes.
    • IRNSS/NAVIC: Indian Regional Navigational Satellite System, four in geosynchronous orbit plus three in medium earth orbit

    Methods of Observation

    • Static
    • Rapid Static
    • Kinematic
    • Real-time Kinematic (RTK)

    Types of Applications

    • Control Surveys
    • Topographic Surveys
    • Replanning
    • GIS-based applications
    • Navigation
    • Tracking

    Additional Notes

    • Different GNSS systems have various orbital characteristics.
    • GNSS technologies are constantly evolving for higher accuracy and availability.

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    Related Documents

    GNSS Systems Introduction PDF

    Description

    Test your knowledge on GNSS positioning methods, their applications, and the technical details of various satellite systems. This quiz covers static and kinematic positioning, errors in GNSS accuracy, and the operational satellites within the IRNSS/NAVIC and NAVSTAR-GPS systems.

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