The first Global Positioning System (GPS) satellite launched in 1978. Today, it’s so widely used by consumers, businesses, and government agencies that the acronym has become a shorthand term for any navigation or location application.
One reason is because GPS pioneered the space — literally. Over the decades, the Global Navigation Satellite Systems (GNSS) sector has grown to include constellations such as Galileo (Europe), GLONASS (Russia), BeiDou (China), IRNSS (India), and QZSS (Japan). (For a comparison of GPS and other GNSS, see “How to Navigate the L1, L2, L5, E5a, E5b, and G2 Alphabet Soup of GNSS Constellations and Signals.”)
What is GPS?
GPS gets the first part of its name from the 31-plus satellites that ring the Earth to provide global coverage. Each satellite circles the planet twice a day in one of six orbits.
The GPS receiver inside a smartphone, fitness wearable, vehicle navigation unit, or Internet of Things (IoT) device receives signals from multiple satellites simultaneously. By comparing the time of arrival for each signal, the receiver can calculate its distance from those satellites and thus its latitude and longitude position on Earth — whether it’s on land or in the middle of an ocean.
GPS is continually evolving, with new satellites and new types of signals. This modernization benefits device OEMs, systems integrators, and end users by increasing performance and reliability. (For more information about the GPS modernization program, see https://www.gps.gov/systems/gps/modernization.)
How Precise is GPS?
GPS initially was limited to military and government users until 1983, when it was opened to civilian applications. However, civilian GPS receivers were limited to an accuracy of about 330 feet (100 meters) until 2000, when that restriction was eliminated.
Today, some applications — such as autonomous vehicles and precision agriculture — have such high accuracy requirements that additional systems are necessary to augment GPS. The two main types are real-time kinematic (RTK) correction services and precise point positioning (PPP) services, which sometimes are referred to as L-Band services. Depending on the type used, these systems can increase accuracy to an area as small as 1 cm. (For more information about PPP and RTK, see “How to Leverage the L-Band to Balance Accuracy and Affordability for GNSS Applications.”)
The Role of Antennas
Correction services also highlight two additional factors: GPS signals are relatively weak by the time they reach the Earth. They can be further weakened by conditions on the ground, such as dense tree cover. So when developing an application that relies on GPS, it’s important to consider where the devices will be used.
This in turn affects the choice of GPS antenna. For example, a mission-critical application such as public safety vehicles will need an antenna with high gain and other attributes that provide the GPS receiver with a reliable signal in any environment. (For a deeper dive, see “Six Key Parameters to Consider When Comparing GNSS Antennas.”)
Right on Time
Although GPS is synonymous with location information, its signals also provide time data that’s accurate to 100 billionths of a second. This accuracy is ideal for applications such as time stamping business transactions and synchronizing infrastructure in telecom networks and electrical grides.
In the process, GPS eliminates the need for devices to include dedicated time sources, such as atomic clocks and atomic clock receivers. This helps simplify device designs and reduce bill-of-material (BOM) costs.
To learn more about how to select the right GPS antenna, speak to Taoglas’ Engineering team by clicking on the button below.
