Question:
I noticed that the history trail of one of my vehicles follows the road with great accuracy until it enters a heavy tree covered area, at which point it begins to slightly deviate from the road. Although I can see that the route generally follows the shape of the road, it does so with much less precision. Why does this happen?
How GPS Units Track Data
A GPS unit receives data from GPS satellites that orbit 12,000 miles above the earth. There are 24+ GPS satellites orbiting the earth at any one time. GPS satellites send satellite location, time, and satellite health information using standard radio frequencies. The GPS unit picks up these radio frequencies, and calculates its location based on triangulation between at least three satellites. This calculation is heavily dependent on time information sent by the satellite, as the time between transmission and receiving of the signal is what is used to determine the distance of the satellite. The GPS unit communicates telematics data to GPS Insight using the cellular network based on the reporting interval for which it is programed.
Accuracy of GPS Technology
After the GPS unit receives information from all satellites within range, the unit calculates the latitude and longitude of the GPS unit. The GPS unit is normally accurate to within two meters Circular Error Probability (CEP), and the accuracy is further increased through algorithms built into GPS Insight. Analysis of the GPS information provided by GPS Insight yields an accuracy rate of approximately 99.88%. In most cases, inconsistencies and erroneous data elements come from a single incorrect reading; as the sample set of data is increased, the more the more accurate and reliable the data becomes (see GPS drift). While not every erroneous piece of data is caught, there are many filters in place to find and eliminate erroneous readings.
Limitations of GPS Technology
Due to all of the independent technologies used to produce GPS data, there are some limitations to GPS technology, which are typically categorized as GPS Drift and Signal Bounce. These limitations are due to factors such as:
- Satellite positioning
- Satellite health status
- Radio frequency interference
- Natural and man-made obstructions
- Atmospheric interference
GPS Drift
GPS drift refers to the magnitude of inaccuracy of a device’s positional data (e.g., the number of meters within CEP). Drift may occur when GPS satellite constellation patterns change, the device enters an area with poor reception, or other conditions that are out of our control. Erroneous data points that are occasionally created by GPS drift are primarily noticeable within calculations that are affected by single points of data, such as instant speed data and g-force calculations. Therefore, this type of data is best used at a summary level.
Signal Bounce
GPS satellites send signals to our units using radio frequencies, which are occasionally subject to interference and signal bounce off of large objects (e.g., buildings, overpasses, and mountains/natural obstructions). When our unit is close to these objects, there is a chance that the signal from the satellite will bounce off of these objects, and cause our unit to incorrectly calculate the timing of the signal, which will affect the unit’s calculation for its location. When this issue does occur, the erroneous data is usually more pronounced than what you would find with GPS drift, and you can typically isolate the cause when reviewing vehicle history (i.e, the vehicle was driving under large overpasses on freeways or traveling through large metropolitan areas surrounded by high rise buildings).
Other Considerations
GPS Insight receives posted speed limit data from third-party vendors. The quality of this information is determined by the municipalities that provide the information to the third-party vendors. Major metropolitan areas have a very high degree of accuracy in regard to posted limits, while rural areas tend to have no posted speed limit data, or outdated data. Additional considerations that impact posted speed limit data include:
- Recent changes in posted speed limits that are not yet reflected in our data
- Construction zones / temporary speed limits
- GPS drift on highways that may be reporting the location of the vehicle on a parallel road or service road
GPS Insight provides you with the ability to report incorrect speed limits within the speed violations report. GPS Insight recommends that users thoroughly research and validate all speed-violation incidents prior to taking any action on a reported speed-violation. Read more about speed definitions.
FAQs
Various factors can affect GPS accuracy, so it's not surprising when smartphone apps give you misleading data. Overall, though, GPS works well enough to pinpoint locations reliably. Depending on your device's GPS technology, though, you could get accuracy anywhere from a millimeter to about five meters.
How accurate are GPS surveys? ›
The accuracy obtained from this method depends on the duration of the observations, but is typically about 1 part per million (1 millimetre per kilometre) so a difference in position can be measured over 30 kilometres with an uncertainty of about 30 mm, or about 100 mm over 100 kilometres.
How effective is a GPS? ›
Modern GPS tracking systems are highly accurate, with most devices capable of providing location data within a range of 3 to 15 meters (9.8 to 49.2 feet).
How accurate is GPS running? ›
And yet it's often not accurate enough for runners. I've frequently heard runners proclaim after races “This course is long” or “this course is short”. As you can see in that original picture the accuracy of GPS in any one moment is questionable.
How accurate is GPS status? ›
With a clear view of the sky, GPS accuracy without differential correction is about 10 meters (32.8 feet). Sub-meter accuracy is reported after applying differential correction when using a second GPS receiver (dual GPS), such as the Trimble GPS Pathfinder Pro XR.
Which GPS system is most accurate? ›
Galileo: Europe's High Precision System
Galileo, the European Union's flagship global navigation satellite system, represents the pinnacle of GNSS technology with a focus on precision and reliability.
Why is GPS not 100% accurate? ›
Many things can degrade GPS positioning accuracy. Common causes include: Satellite signal blockage due to buildings, bridges, trees, etc. Indoor or underground use.
How do I check my GPS accuracy? ›
Measure the distances between all points (triangles) with a measuring tape or laser distance measurer. Determine the positions of these points with your GPS: Fasten the device motionless for at least one minute at each point.
Which one is the disadvantage of GPS survey? ›
Disadvantages of GPS are that it completely relies on receiving satellite signals by radio, so can be prone to nuclear weapons EMP, radio interference, and failed satellites.
How accurate is GPS on Google Maps? ›
GPS: Maps uses satellites to know your location up to around 20 meters. When you're inside buildings or underground, the GPS is sometimes inaccurate. Wi-Fi: The location of nearby Wi-Fi networks helps Maps know where you are. Cell tower: Your connection to mobile data can be accurate up to a few thousand meters.
GPS technology is generally reliable for long road trips, especially when using dedicated GPS devices that connect directly to satellites. These devices tend to be more accurate and can function in remote areas without cellular coverage.
Is A GPS more accurate than a cell phone? ›
The algorithms used to calculate GPS positions vary depending on the device. Dedicated GPS tracking devices often use sophisticated data filtering and processing algorithms to increase accuracy. Smartphones may use simpler algorithms, sacrificing precision in favor of battery life and processing power.
How accurate is GPS data? ›
GPS is typically only accurate to, at best, around 10 feet or 3 meters in direct view of a clear sky.
How accurate is the US GPS system? ›
Signal arrival time measurement
The position accuracy is primarily dependent on the satellite position and signal delay. , or approximately 10 nanoseconds for the C/A code. Since GPS signals propagate at the speed of light, this represents an error of about 3 meters. or about 30 centimeters.
How accurate is GPS in cities? ›
Urban Areas: Urban environments present unique challenges for GPS accuracy. Tall buildings and narrow streets can obstruct signals and cause multipath interference, where signals bounce off structures and lead to errors. This phenomenon, known as “urban canyon” effect, can significantly degrade GPS precision in cities.
Is GPS location 100% accurate? ›
GPS satellites broadcast their signals in space with a certain accuracy, but what you receive depends on additional factors, including satellite geometry, signal blockage, atmospheric conditions, and receiver design features/quality. For example, GPS-enabled smartphones are typically accurate to within a 4.9 m (16 ft.)
Can GPS make mistakes? ›
GPS signals can also be affected by multipath issues, where the radio signals reflect off surrounding terrain; buildings, canyon walls, hard ground, etc. These delayed signals cause measurement errors that are different for each type of GPS signal due to its dependency on the wavelength.
Do GPS trackers show the exact location? ›
GPS trackers are equipped with a built-in GPS receiver that allows them to receive signals from GPS satellites and determine their precise location. This enables GPS trackers to provide accurate location data even in remote or isolated areas where cell phone coverage may be limited.
Is there anything more accurate than GPS? ›
A new hybrid optical-wireless network has been developed for navigation that is far more robust and accurate than GPS, especially in urban settings. Researchers have developed an alternative positioning system that is more robust and accurate than GPS, especially in urban settings.
A GPS unit receives data from GPS satellites that orbit 12,000 miles above the earth. There are 24+ GPS satellites orbiting the earth at any one time. GPS satellites send satellite location, time, and satellite health information using standard radio frequencies. The GPS unit picks up these radio frequencies, and calculates its location based on triangulation between at least three satellites. This calculation is heavily dependent on time information sent by the satellite, as the time between transmission and receiving of the signal is what is used to determine the distance of the satellite. The GPS unit communicates telematics data to GPS Insight using the cellular network based on the reporting interval for which it is programed.
After the GPS unit receives information from all satellites within range, the unit calculates the latitude and longitude of the GPS unit. The GPS unit is normally accurate to within two meters Circular Error Probability (CEP), and the accuracy is further increased through algorithms built into GPS Insight. Analysis of the GPS information provided by GPS Insight yields an accuracy rate of approximately 99.88%. In most cases, inconsistencies and erroneous data elements come from a single incorrect reading; as the sample set of data is increased, the more the more accurate and reliable the data becomes (see GPS drift). While not every erroneous piece of data is caught, there are many filters in place to find and eliminate erroneous readings.
GPS satellites send signals to our units using radio frequencies, which are occasionally subject to interference and signal bounce off of large objects (e.g., buildings, overpasses, and mountains/natural obstructions). When our unit is close to these objects, there is a chance that the signal from the satellite will bounce off of these objects, and cause our unit to incorrectly calculate the timing of the signal, which will affect the unit’s calculation for its location. When this issue does occur, the erroneous data is usually more pronounced than what you would find with GPS drift, and you can typically isolate the cause when reviewing vehicle history (i.e, the vehicle was driving under large overpasses on freeways or traveling through large metropolitan areas surrounded by high rise buildings).