What is GPS?
Developed by the U.S. government, the Global Positioning System “GPS” receive signals from these satellites and use them to pinpoint and track the location of the device, generally within a few yards under optimal conditions. Trackers use multiple satellites to triangulate their position, so the more satellites the device can “see,” the more accurate it will be in pinpointing its location.
GPS satellites fly in medium Earth orbit (MEO) at an altitude of approximately 20,200 km (12,550 miles). Each satellite circles the Earth twice a day.
The satellites in the GPS constellation are arranged into six equally-spaced orbital planes surrounding the Earth. Each plane contains four “slots” occupied by baseline satellites. This 24-slot arrangement ensures users can view at least four satellites from virtually any point on the planet.
How GPS Works
GPS satellites circle the Earth twice a day in a precise orbit. Each satellite transmits a unique signal and orbital parameters that allow GPS devices to decode and compute the precise location of the satellite. GPS receivers use this information to calculate a user’s exact location. Essentially, the GPS receiver measures the distance to each satellite by the amount of time it takes to receive a transmitted signal.
How Accurate is GPS?
It depends. 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 smart phones are typically accurate to within a 4.9 m (16 ft.) radius under open sky; However, their accuracy worsens near buildings, bridges, and trees.
High-end users boost GPS accuracy with dual-frequency receivers and/or augmentation systems. These can enable real-time positioning within a few centimeters, and long-term measurements at the millimeter level.
Why does GPS sometimes show me in the wrong place?
Many things can degrade GPS positioning accuracy. Common causes include:
- Satellite signal blockage due to buildings, bridges, trees, etc.
- Indoor or underground use
- Signals reflected off buildings or walls (“multipath”)
Far less common causes may include:
- Radio interference or jamming
- Major solar storms
- Satellite maintenance/maneuvers creating temporary gaps in coverage
- Improperly designed devices that do not comply with GPS Interface Specifications
In many cases, a device’s GPS hardware is working fine, but its mapping software is faulty. For example, users are often misled by:
- Incorrectly drawn maps
- Mislabeled businesses and other points of interest
- Missing roads, buildings, communities, etc.
- Incorrectly estimated street addresses
What is the government’s commitment to GPS accuracy?
The government is committed to providing GPS at the accuracy levels specified in the GPS Standard Positioning Service (SPS) Performance Standard.
The accuracy commitments do not apply to GPS devices, but rather to the signals transmitted in space. For example, the government commits to broadcasting the GPS signal in space with a global average user range error (URE) of ≤7.8 m (25.6 ft.), with 95% probability. Actual performance exceeds the specification. On May 11, 2016, the global average URE was ≤0.715 m (2.3 ft.), 95% of the time.
To be clear, URE is not user accuracy. User accuracy depends on a combination of satellite geometry, URE, and local factors such as signal blockage, atmospheric conditions, and receiver design features/quality.
The ongoing GPS modernization program will further improve accuracy for civilian and military users.
How accurate is GPS for speed measurement?
As with positioning, the speed accuracy of GPS depends on many factors.
The government provides the GPS signal in space with a global average user range rate error (URRE) of ≤0.006 m/sec over any 3-second interval, with 95% probability.
This measure must be combined with other factors outside the government’s control, including satellite geometry, signal blockage, atmospheric conditions, and receiver design features/quality, to calculate a particular receiver’s speed accuracy.
How accurate is GPS for timing?
GPS time transfer is a common method for synchronizing clocks and networks to Coordinated Universal Time (UTC). The government distributes UTC as maintained by the U.S. Naval Observatory (USNO) via the GPS signal in space with a time transfer accuracy relative to UTC(USNO) of ≤40 nanoseconds (billionths of a second), 95% of the time. This performance standard assumes the use of a specialized time transfer receiver at a fixed location.
How a GPS Tracker Works
GPS tracker requires two antennae, one for GPS and another for cellular. The size of the GPS antenna will affect how well the chip receives data from the Global Positioning System, and therefore the device’s accuracy.
Second is the issue of power. Anyone with a smart phone knows that it’s difficult to get more than an hour or two of consistent use from a device sending and receiving data. A GPS tracking device must consistently receive GPS data from the satellite network and report its position through a cellular network GSM (Global System for Mobile Communications, originally Groupe Spécial Mobile) to be of any use. Our trackers have a built in 4.2V internal rechargeable battery.
GSP Trackers report their positions at a predetermined interval and are programmed based on the needs of the user. This will be determined through a variety of factors, such as the tracker’s size, what’s being tracked, and expected cellular and GPS coverage in the area, among others. Commonly, the fastest reporting interval for most trackers is every 5-10 seconds.
By not sending a continual stream of data, the tracker can conserve power and potentially operate for weeks, or even months, in some cases, on a single charge. Meanwhile, a tracker set for constant data would likely last only a few hours at best. It also helps keep costs down. For most applications, reporting every few minutes is more than adequate.
So, a tracker sends its location at a predetermined interval, which the GPS platform displays as a point on a map. This usually takes a few seconds to process (depending on network traffic). It sends data this way to provide tracking for as long as possible at the best price.
GPS Tracker vs. GPS Navigation
A GPS tracker and a GPS navigator work a bit differently. A navigator will usually come loaded with a set of maps that are current as of its time of programming. These are stored to the device’s memory. The device then receives signals from the GPS satellite constellation which provides it with its own coordinates. The navigator translates those coordinates into a position on a map that’s displayed on your navigator’s screen. Which only allows the person in the car to see where the car is at currently and not able to track via computer or smart phone. Most companies will provide navigator updates every few months, offering you updated maps for a small fee.
A GPS tracker, on the other hand, receives its data from the Global Positioning System and transmits its location via cellular service to a tracking platform which will translate its coordinates into a point on a map. Most will use a standardized mapping service, like Google Maps, so that they’re kept up-to-date without requiring a user to take action.
GPS trackers also have the ability to be hand held or hardwired depending on your type of use therefore you can track more than just your car but any asset your desire with the ability to monitor the tracker at anytime via computer, ipad, or any smart phone.
While a small amount of a monthly monitoring fee goes to the upkeep and maintenance of the platform that keeps the tracker running, the lion’s share is the cost of monthly cellular data. Each “locate” being sent over the cellular network represents a small charge, but they add up over the course of the month.
The government’s GPS satellites are one-way beacons that cannot track you or anything on the ground. But commercially available GPS devices with communication or recording features can help users keep track of everything from vehicles and cargo to people and animals.
The use of GPS technology to covertly monitor suspects, employees, customers, and other people raises questions about individual privacy rights. Several lawsuits and legislative actions have sought to address these questions, but much remains unresolved today.
The Fourth Amendment to the U.S. Constitution grants Americans certain privacy rights by protecting them from “unreasonable searches and seizures” and by requiring search warrants to be based on “probable cause.” As of October 2014, it remains unclear whether the extended use of GPS technology to track suspects without a warrant violates their Fourth Amendment rights.
Several U.S. states and non-U.S. jurisdictions have enacted laws establishing personal location privacy rights. However, current U.S. statute at the federal level does not provide clear protection of geolocation information.
Members of Congress have proposed legislation to prevent misuse of such information by law enforcement, companies, and individuals. These include the Geolocation Privacy and Surveillance Act (“GPS Act”), the Online Communications and Geolocation Protection Act, and the Location Privacy Protection Act. As of October 2014, none of these bills has been enacted into law.
In January 2012, the U.S. Supreme Court ruled that law enforcement must obtain a warrant before physically attaching a GPS tracking device to a suspect’s vehicle. The decision (United States v. Antoine Jones) was based on a narrow application of the Fourth Amendment, since device installation involves physical intrusion on a suspect’s vehicle. The Supreme Court did not resolve the broader issue of whether the Fourth Amendment protects geolocation privacy rights.
In a separate case decided in June 2014, the Supreme Court ruled that police need a warrant before searching the contents of a suspect’s cell phone. The opinion (Riley v. California) specifically discusses the location history stored inside a phone (often collected automatically via GPS) as an example of personal information deserving protection from unwarranted disclosure.
What private citizens need to know about GPS tracking and the law:
GPS Tracking is an easy and affordable way to monitor a person, vehicle, or asset. With minimal effort, you can know where someone is, where they’ve been, where they’re going, and how fast they’re traveling. GPS is a great option for parents concerned about their children getting to school safely, or business owners looking to optimize their fleet of vehicles. Before you decide to begin tracking, however, it’s important to consider the legality of your GPS solution.
For starters, it’s entirely legal to use a GPS tracking device on any vehicle or asset you own. But before you use a GPS tracking device on someone else’s person, vehicle, or property, you should do a little research on current federal, state, and local laws. Laws are continually being readdressed as new cases are popping up in the legal world, so it’s important to stay up-to-date on the these changes.
It’s legal to use a GPS tracking device if:
- You or your organization own the vehicle or asset to be tracked
- You own the asset that might be taken without your permission
- Your children (under 18) are the focus of the tracking
- You are tracking a car or asset for the purpose of legal repossession in the event of a default on a loan
It’s illegal to use a GPS tracking device if:
- You are not the owner of the car and do not have the legal right to track it
- You are attempting to track a boyfriend, girlfriend or non family member in their own car
Court Cases That Have Changed GPS Laws
Since the introduction of GPS trackers to the marketplace, court cases and lawsuits addressing the ethical and legal uses of these devices to monitor the movements of others have multiplied. Some of these cases have addressed the legality of law enforcement officials using these devices to track private citizens, while others have been concerned with civilians using them to track their significant others, employees, children, and others. The dialogue about this topic remains ongoing as technology advances and applications for trackers increases.
In 2012, the Supreme Court ruled that the government and law enforcement agents are not permitted to install GPS devices on a person or property of a person based on suspicion of lawbreaking unless a warrant is obtained first. Federal law has not specifically addressed whether it is legal or illegal for a private citizen to track another person, vehicle, or property, but a number of states have addressed the question. For example, in California, Texas, Virginia, and Minnesota, is it legal to use a GPS tracker on a vehicle as long as the vehicle’s owner has provided consent, while in Wisconsin, for example, a person could face criminal charges for using a GPS tracker on another person’s vehicle without permission. It’s important to consult local and state laws, or speak with an attorney for any clarification.