How reliable are GPS tracker reports when it comes to speeding?

The issue of insurance claims being rejected or individuals facing criminal charges based on speed data obtained from “Tracker Reports” is a common occurrence.

In many countries where asset recovery is a significant concern, most modern vehicles are equipped with a “Tracking System,” either installed by design or retrofitted. In South Africa, for example, where vehicle hijacking and theft are rampant, insurers often require the installation of a “VESA-approved tracking and recovery device” as a condition for coverage.

In reality, the VESA standard is quite ambiguous. The website of the Motor Vehicle Security Association of South Africa (VESA) outlines the following guidelines in relation to their standards:

VESA / ABS Category Descriptions:

  • Category A (Stolen Vehicle Recovery systems)
  • Category B (Fleet Management systems)
  • Category C (Stolen Vehicle Recovery & Fleet Management systems)

A consumer (Business or individual) is advised to at least confirm the following when making a tracking selection:

  • Could reliable recovery statistics be provided? Is there independent auditing by a third party for these statistics?
  • Could the suppliers’ vehicle tracking products be tested for compliance against accepted international standards?
  • Are the installation methods used safe, tested, and compliant with VESA installation standards in terms of people and vehicle safety, integrity, and security?
  • Could you please provide more context or background information on the topic you are referring to? This will help me to provide a more accurate and relevant response.

If the consumer contacts the tracking company, can the consumer request and obtain the position of their vehicle from the tracking company with proper authorization, or is there a self-service option available?

Taking this into consideration, it becomes clear that the standard mainly pertains to the installation and functionality of the tracking system rather than its use or application. It is important to note that many individuals, including some experts who are called upon to testify in court, have a limited understanding of the technology and, more significantly, its limitations.

GPS Tracking is essentially a collection of GPS Location Data that is processed and presented in a human-readable format. This data usually includes information such as the vehicle identification number, time of location, driver identification, status, and the most scrutinized piece of data – speed.

But how is this data collected, exactly? When the “Tracker Report” indicates a “speed,” how was that determined, how accurate is it and where did it come from? In order for us to answer these questions, we need to have a basic understanding of how GPS Technology actually works, what a “Tracking Device” is, and how they interact to where this report is available.

In simple terms, GPS Technology consists of three components: The Control Segment, the Space Segment, and the User Segment. 

The Control Segment of the GPS system comprises the command centers and up-links that transmit updated data to a network of satellites and maintain them. Although the satellites are not fully autonomous, as their exact position and location in space and relative to Earth need to be constantly monitored and updated to maintain their accuracy. The current Operational Control Segment (OCS) includes a master control station, an alternate master control station, 11 command and control antennas, and 16 monitoring sites.

The Master Control Station assumes responsibility for high-level control tasks such as commanding and controlling the GPS Constellations, computing their precise locations, uploading navigation messages, and monitoring broadcast and system integrity to ensure the health and accuracy of the constellation. On the other hand, the Monitor Stations track the GPS Satellites as they travel overhead, collect navigation signals, range/carrier measurements, and atmospheric data, and provide observations to the master control station. The Ground Antennas are responsible for sending commands, navigation data uploads, and processor program loads to the satellites, collecting telemetry, and performing S-band ranging to provide early orbit support and anomaly resolution.

Although the technical aspects of the GPS system can seem complex, it is important to recognize that significant resources, including advanced technology and human expertise, are employed to ensure that the system operates optimally. This includes ensuring the precise placement of satellites, ongoing monitoring and updating of satellite data, and other critical tasks necessary for the effective functioning of the GPS constellation. Ultimately, these efforts are aimed at providing accurate and reliable data to end-users seeking to utilize the system for navigation or other purposes.

The Space Segment of GPS technology comprises all currently operational and active satellites in orbit, and is constantly growing and advancing. As the technology has evolved, several countries have entered the field and launched their own satellites. The US was the first to launch the original GPS System in 1978, followed by Russia with GLONASS in 1982, China with BeiDou in 2000, the European Union with Galileo in 2011, and India with NavIC and Japan with QZSS in 2018.

In the realm of GPS technology, not all satellites are created equal. As time has passed, advancements in technology have led to the development and launch of new iterations of GPS satellites that offer improved accuracy and reliability. Most importantly, these advancements have focused on mitigating the potential for spoofing and hacking interference.

Satellite technology can effectively be separated into various “Blocks” which currently include:

  • Blocks IIA, Launched in 1990-1997, with the last one decommissioned in 2019.
  • Block IIR, Launched in 1997-2004.
  • Block IIR-M. Launched in 2005-2009.
  • Block IIF, Launched in 2010-2016.
  • GPS III/IIIF, First Launched in 2018.

In terms of current developments, the US Space Force announced that the first GPS III Satellite was available for public use in January 2020. By November 5th of the same year, the Space Force and its partners successfully launched the fourth GPS III satellite into orbit. By December 2020, the latest GPS Technology, GPS III SV-04, received operational acceptance. As of January 2021, there were 31 GPS satellites in orbit and operational, under US control. However, as of November 6th, 2020, there were a total of 76 satellites in orbit, 31 of which were operational, 9 in reserve, 3 being tested, 30 retired, 2 lost at launch, and 1 launched on November 5th, 2020. The GPS constellation requires a minimum of 24 operational satellites, with a typical number of 31 being active.

In terms of the User Segment, the primary focus lies on the “Public Consumer” use, specifically vehicle tracking and recovery, as opposed to the Marine, Aviation, Military, Industrial, Research, and Education Segments. Public Consumers primarily utilize GPS Technology for Vehicle Navigation, Cell Phone Geolocation, Vehicle Tracking and Recovery, Racing, among other applications. However, it’s important to discuss the role of receivers, which are the devices used to receive and interpret GPS Data.

The typical GPS tracking and recovery unit installed in a motor vehicle contains a small box that houses a few key components.  The key components of a typical GPS Tracking and Recovery Unit include:

GPS Receiver or Module (including an antenna, to receive the GPS Signal).

  • Microprocessor (for interpreting the raw GPS data).
  • Power Supply (for connecting to power).
  • Alarm Inputs (Tamper prevention).
  • SIM Card (for sending data).

The GPS device is typically installed in a concealed location inside the vehicle. However, it is important to avoid locations with excessive signal interference that can affect the signal accuracy. The GPS signal can be influenced by various factors, and any interference can have a negative impact on the accuracy of the device.

The things that could affect GPS Signal Quality, and therefore positional accuracy, could include:

  • Selective Availability – Intentional GPS Location Changes for military operations.
  • Ephemeris Error – Faults in the exact reported or recorded location and position of Satellites.
  • Clock Error – Imperfections in the tracking of time, by GPS Atomic Clocks.
  • Multipath Error – The path the signal follows from Satellite to Receiver, like reflecting off surfaces or buildings.
  • System Noise – Things like internal components, radio, or electromagnetic noise.
  • Antenna Phase Center Variations – Imperfections in the design of the receiver antenna or its immediate environment (car parts).
  • Ionospheric or Tropospheric Delays – Slowing of the GPS Signal due to various atmospheric layer conditions.
  • Geometric Effects – Errors in calculations and angular measurements.

Due to the constant movement of vehicles and their proximity to various physical structures such as buildings, trees, mountains, valleys, high tension power wires, cell phone towers, and other radio sources, GPS accuracy can be adversely affected. Furthermore, the presence of cell phones inside vehicles can also contribute to signal interference and reduce the accuracy of the system over time.

GPS accuracy can be measured in two ways: User Range Error (URE) and User Range Accuracy (URA). While it can be difficult to explain the factors that affect accuracy (URE), it is easier to define the level of accuracy that can be achieved (URA).

In order to provide a more accurate understanding of GPS accuracy, it is important to distinguish between two types of measures: User Range Error and User Range Accuracy. Often, dedicated GPS devices such as the Garmin eTrex will display an “accuracy value” that should not be confused with the device’s current accuracy. Instead, this value represents the potential accuracy that could be achieved under optimal conditions with direct reception from all signals, including knowledge of the current quality of each satellite signal received. The displayed value is not a measure of the device’s accuracy at that moment, but rather an estimation of the accuracy that could be achieved if all conditions were ideal, including the presence of current and properly set data for all satellites, no signal interference, and no time-of-flight errors (including Ionospheric or Tropospheric Delays). For instance, if the device is connected and “locked onto” seven satellites with varying signal strengths, an accuracy of 18ft (about 5.5m) would be achievable under these ideal conditions.

In simpler terms, let us consider a person walking a distance of 200 feet in 100 strides with a stride length of exactly 2 feet. This would be true only if the person’s gait and stride lengths were perfect. However, in reality, the person may have a shorter leg or may step over pebbles, which could affect the accuracy of the distance they cover. Similarly, GPS technology is prone to errors that affect its accuracy. The “accuracy value” displayed on a GPS device only shows the accuracy that can be achieved under optimal conditions, with no signal interference or time-of-flight errors. Therefore, it is important to understand that GPS technology is not 100% accurate and can have inaccuracies just like any other measurement system.

In the context of GPS technology, it is a common misconception, even among court experts, that a “Tracking Device” receives “GPS Location Data.” However, this is entirely false. The only information that a GPS Receiver ever receives is time, which is part of a larger package of non-location data contained in a Rinex File. To elaborate, a GPS Satellite, which knows its position from Ground Segment Updates, sends a signal to the receiver, along with the time that the signal was sent. The “Tracking Unit” essentially uses this information to determine a position, and it does not actually receive GPS location data.

In the context of GPS technology, the distance between the GPS tracker and a satellite can be calculated by comparing the time the signal was sent with the time of its arrival. To draw an analogy, consider a person named Bob who left his home at 1 PM and arrived at Peter’s house at 2 PM. Assuming that Bob typically walks at 5 Km/h, we can calculate that he covered 5 Km. However, we cannot determine the location of Peter’s house without knowing where Bob started from. If Bob had five friends who also walked from their homes to Peter’s house, and we knew the location of their houses, we could estimate the location of Peter’s house with reasonable accuracy. However, this would only be possible if they all walked in a straight line without any turns or stops, as these factors could affect our assumptions.

GPS trackers function similarly to the example of Bob and his friends walking to Peter’s house. Like the example, GPS trackers are prone to errors and inaccuracies if the exact locations of the satellites, signal interference, and the exact path followed are not known. In other words, the distance data obtained from the GPS tracker may not be accurate, which in turn affects the accuracy of the location data provided by the tracker.

In this discussion, let’s focus on speed, which is the most important concern. The measurement of speed in tracker reports is not done in a conventional way. There is no direct connection, such as a data or mechanical link, between the GPS receiver and the vehicle. Even if the vehicle’s wheels are spinning, the speed indicated on the speedometer may not be reflected on the tracker report. Similarly, if the vehicle is on a high-speed train with the engine turned off, the tracker report may indicate an inaccurate speed as “Speeding” or “Overspeed.”

In order for your speed to be reported, the GPS Tracking System will essentially make a number of assumptions:

  • It will assume that all position data is 100% accurate – even if it is only connected to one satellite or has very weak satellite signals.
  • It will assume that all times are 100% accurate – even though it is not equipped with an atomic clock that is regularly updated.
  • It will assume that all movements are 100% accurate – even though you might be turning corners or going up or down some hills.
  • It will assume that your vehicle followed a straight line – even though you might be driving in circles.

The process of calculating speed in GPS tracking involves dividing the distance between two positions by the time taken to travel between them, without taking into account any errors or assumptions. Some GPS tracking systems are equipped with a base map, which can normalize the vehicle’s position to the nearest road, as if it were providing navigation input. Furthermore, if the GPS signal is lost, the system may still assume the vehicle’s continued position and time data based on its historical movements. For instance, passing through a tunnel where the GPS signal is not available may not always result in a “signal lost” message, depending on the tracking system used.

In the aforementioned scenario, the distance between two points will be computed as the distance traveled during 60-second intervals. The tracking device will adopt a 2-dimensional model and determine the speed by calculating the time taken by the vehicle to cover a specific distance, which in this case is 1000m in 60 seconds. This computation results in a speed of 60 Km/h. However, as the example illustrates, the vehicle traveling through bends covers a greater distance than the one traveling in a straight line, although both cover a straight distance of 1000 m. The Tracking System is unaware of this fact and will still report a speed of 60 Km/h, whereas the vehicle was, in reality, traveling at a speed of 90 Km/h. Therefore, the “Tracker Report” will display a value with an error of 50%.

The issue of inaccurate location is the main reason for the errors observed in Tracker Reports, rather than problems with time. Our analysis of real-world cases has shown that these errors can be as high as 80% or more due to overestimation.

GPS Tracking Units are highly valuable tools for vehicle recovery purposes, assuming they have not been intentionally disrupted or removed. Over time, these devices can lead recovery agents to a vehicle, typically within a few hundred meters or less. While the errors in location data can fluctuate dynamically, they do not generally cause vehicles to appear significantly farther from their actual location (unless selective availability is activated). As a result, vehicles can be located relatively easily and identified by recovery agents who typically have specific information about the vehicle in question. For recovery purposes, GPS Tracking Units are effective tools.

In terms of recording speed, GPS tracking devices are not the most reliable and can generate results that are inconsistent and even unrealistic when compared to actual data. As a result, we recommend against relying solely on “Tracker Reports” for this purpose. When using speed data provided by tracking devices, it is best to cross-reference it with evidence from the real world. Our observations indicate that these reports, when thoroughly analyzed, are frequently unreliable, prone to errors, and not particularly useful in isolation.

The analysis of Tracker Reports is a complex process that cannot be fully explained in this article. However, it is essential to understand why Expert Witnesses should be cross-examined on their reliance on these reports, why an Expert Witness may be required in cases where speed is derived from Tracker Reports, and why the data must be carefully scrutinized and individually verified. It is critical to ensure the accuracy of the information presented in court, and a qualified expert can help in this regard.

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