Podcast
Questions and Answers
Multipath refers to the use of direct signals in GPS measurements.
False
The GPS system is considered to be a Global Navigation Satellite System (GNSS).
True
Ionospheric delay is an internal problem that affects GPS measurements.
True
BeiDou-2 is considered the smallest current operational GNSS.
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Change-based measurements occur when a certain event happens in a specific location.
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The control segment of GNSS includes receiver devices.
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Scintillation refers to sudden variations in the refractive index affecting GPS signals.
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An event-based measurement is triggered at regular time intervals.
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GPS measurements can be negatively impacted by receiver noise.
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The space segment of GNSS includes satellite transmitters.
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Study Notes
Measured Data
- Track points are part of a track and are automatically recorded
- Track points are interval based including time and changes over time
- Waypoints are points of interest (POI)
- Measured data captures information purposefully, independently, and with meaning
How does the pace segment work?
- Location is measured as the distance between ranging master and object
- Deviation is the difference in the measured distance caused by random noise
- Random noise includes scintillation and multipath
- Scintillation is caused by sudden variations in the refractive index
- Multipath is caused by indirect signals
- Distance (L) is determined by the speed of light (c) and the difference between the measured time intervals (t2−t1t_2 - t_1 t2−t1)
- L=c∗(t2−t1)L = c * (t_2-t_1)L=c∗(t2−t1)
- For systems with 3D capabilities, distance is determined by the square root of the sum of the squared differences in the x, y, and z coordinates:
- L=sqrt((x2−x1)2+(y2−y1)2+(z2−z1)2)L = sqrt((x_2-x_1)^2 + (y_2-y_1)^2 + (z_2-z_1)^2)L=sqrt((x2−x1)2+(y2−y1)2+(z2−z1)2)
Error Sources
- Internal problems within space segment include Satellite clock errors, Ionospheric delay, and Troposphere delay
- Multipath and receiver noise are the most common errors, impacting the performance of the measurement system
- Applying a system of satellites and ground stations that provide GPS signal corrections can significantly improve position accuracy
Off Measurement Approaches
- Time-based measurement is collected at regularly spaced intervals
- Location-based measurement is triggered when a position is different from the previous one, or when it falls within a certain proximity
- Change-based measurement is triggered by the occurrence of a specific event at a particular location
- Event-based measurement is triggered when specific events occur, such as phone calls, SMS messages, or public speech
Global Navigation Satellite Systems (GNSS)
- Current operational GNSS systems:
- GPS (United States): Largest global coverage
- GLONASS (Russia): Smallest global coverage
- BeiDou-2 (China): Largest global coverage
- Galileo (European Union): Smaller global coverage
- GNSS components:
- Space segment: Satellites transmitting signals
- Control segment: Base stations correcting signals by uploading correction files
- User segment: Receivers interpreting the signals
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Description
This quiz focuses on measured data and pace segment mechanics in navigation systems. Explore key concepts such as track points, waypoints, and the effects of random noise on location measurements. Understand the formulas used to determine distance accurately.