Garmin faces ongoing competition from other GPS makers such as Magellan and TomTom, who also vie for consumer trust and GPS sales. Providing GPS units that are accurate is one way that Garmin strives to stay competitive. There are two main ways that Garmin GPS units stay accurate: by locking on to multiple GPS satellite signals and by correcting those signals once they reach the earth.
In order for a GPS unit to function properly, it needs to get a signal from three GPS satellites. Garmin GPS devices have 12 different channels that wait to receive signal from GPS satellites. Once these channels receive signal, they lock on to the signal and maintain a strong hold, preserving a continuous flow of GPS data and thus enabling an accurate reading.
Garmin reps claim that this 12-channel setup can maintain signal reception even in dense foliage or urban settings with tall buildings.
The signals from GPS satellites have to travel a long way to get to the earth, so once they arrive they’re not always in accurate form. Disturbances in the ionosphere and atmosphere and satellite orbit errors especially contribute to signal errors. To correct this, Garmin GPS units rely on a technology known as the Wide Area Augmentation System (WAAS).
This system has at least 25 reference stations on the ground that monitor GPS satellite data. This data corrects any errors and sends a message via two ground-based satellites to Garmin GPS units, thereby providing a more accurate reading.
Garmin reps say that because of WAAS and Garmin technology as a whole, Garmin GPS units provide readings that are accurate within three meters. Without WAAS — which is available only in North America, as of 2013 — Garmin devices are accurate within 15 meters, on average.
The WAAS three-meter average is expected 95 percent of the time. So there’s a five percent chance that the reading on your Garmin unit is actually off by a distance greater than three meters.
Technology editors at PC Magazine in 2012 gave a Garmin device — the Garmin nuvi 3590LMT — their Editors’ Choice stamp, largely because of its accuracy in comparison with other brands. Furthermore, a field study from the University of Wisconsin showed that a Garmin handheld device proved more accurate than a Magellan device. However, the Garmin is not problem-free.
The same PC Magazine review noted two occasions when the Garmin nuvi 3590LMT gave inaccurate direction in urban areas of New Jersey and New York. Because all Garmin models use similar circuitry, you can expect somewhat similar results across the Garmin board.
Still, all things considered, reviews have shown that Garmin will most often lead you in the right direction.