AGPS – A technology to improve GPS performance

by Christian Hansen

14. May 2024

In today’s world, the need for accurate and reliable location services is greater than ever before. Today, countless applications are based on GPS technology. And this technology continues to develop over the years. One of the improvements in this area is Assisted GPS (AGPS), a technology that enables faster positioning, improved accuracy and lower power consumption. In this post, let’s take a look at AGPS together to understand how it works.

A short introduction to GPS

Before we dive into AGPS, let’s cover the basics of GPS. The Global Positioning System, consisting of a constellation of satellites orbiting the Earth, allows devices equipped with GPS receivers to determine their precise location anywhere on the planet. By triangulating signals from multiple satellites, GPS receivers can calculate latitude, longitude, altitude and even speed.

A more detailed explanation of how to determine a position using GPS can be found in our article How GPS Works: How Your Device Knows Where You Are

Assisted GPS (AGPS)

While traditional GPS is a wonder in itself, it has its limitations, especially in urban environments with tall buildings or areas with limited sky visibility.

Find out more about how the GPS signal is affected in our article: The exact position: What factors influence the GPS signal?

This is where AGPS comes in to expand and refine the GPS experience. AGPS uses additional data sources beyond satellite signals to improve performance.

This is how AGPS works: Use of assistance data

The focus of AGPS is the use of support data from various sources such as mobile networks, Wi-Fi hotspots and dedicated AGPS servers. This auxiliary data includes important information such as ephemeris and almanac dates, as well as precise time information. By accessing this data, AGPS-enabled devices can speed up the GPS fixation process.

Ephemeris data

Ephemeris describes satellite data that contains the precise positions of GPS satellites and the prediction of their movements. They are broadcast by every GPS satellite. They provide the GPS receiver with information about the orbits, speeds and positions of the satellites in real time.

A GPS receiver must update the ephemeris data regularly (at least every two hours) to continue to enable accurate positioning.

Almanac data

Almanac data is not as precise as ephemeris data, but is valid for a longer period of time. They are not necessary for determining your position, but they are useful. The almanac data makes it possible to speed up the cold start when turning on the GPS receiver, so that a position can be found more quickly. This is possible because the data limits the (frequency) range to be searched. It is still possible to plan GNSS sessions using the almanac data. Because the data can be used, for example, to determine whether and when particularly good results can be achieved at a point on the earth’s surface.

Accelerating the determination of a fix: The AGPS advantage

One of the most significant advantages of AGPS is its ability to speed up the acquisition of a GPS fix. Traditional GPS receivers may take a long time to obtain a location because they only collect and process data from satellites. AGPS-enabled devices, on the other hand, use the aforementioned auxiliary data (ephemeris, almanac) to narrow the search area for satellites, resulting in faster fix times, especially in demanding environments.

GPS fix

A GPS fix describes the process that GPS receivers perform until they have determined an accurate position from the satellite information they receive. AGPS makes it possible to accelerate this process with additional data.

Increased Accuracy: Combining signals for precision

In addition to speed, AGPS improves location accuracy by combining satellite signals with data from other sources such as cell towers and WiFi access points. This signal fusion allows AGPS devices to calculate positions more accurately, even in urban canyons or densely populated areas where GPS signals may be attenuated or multipath interference is prevalent.

Optimizing energy efficiency: extending battery life

Another compelling aspect of AGPS is its ability to save battery power. By reducing the time and resources required for GPS tracking, AGPS-enabled devices use less energy, extending battery life. This efficiency is particularly valuable for mobile devices such as smartphones, wearables and GPS trackers, where battery life is a critical factor.

Conclusion

In summary, Assisted GPS represents a significant advance in location-based services and offers the opportunity to significantly improve the speed, accuracy and energy efficiency of GPS receivers.

Of course, the Prothelis GPS trackers also use APGS technology to enable faster and more energy-efficient positioning.