The image below shows a track recorded by a GPS handheld device that was turned on and recording inside a building. This illustrates what it would look like if you were to record GPS while standing still in a highly degraded GPS environment.
Select your product to confirm this information applies to you
Improving GPS, Distance, and Speed Accuracy of an Outdoor Handheld or GLO 2
The satellite signals that Garmin handhelds and the GLO™ 2 sensor use to determine your location and track your movements are impacted by weather, overhead cover, and terrain.
The information below goes over a number of factors that can affect the accuracy of position, distance and speed readings, and steps that can be taken to prevent or minimize those inaccuracies.
GPS Drift and Environmental Factors
What is GPS Drift?
Consumer grade GPS receivers (such as the ones Garmin makes) are not 100% accurate. GPS Drift, in the most practical sense, is the difference between your actual location and the location recorded by a GPS receiver.
The GPS location accuracy of Garmin handhelds is around 3 meters (10 feet), 95% of the time. This means, at any given time, your handheld will save your location within 3 meters of your actual location. If your handheld is recording a location every second and you do not pause an activity while standing still, your handheld can record up to 180 meters (590 ft) in just 1 minute. When in an area with degraded GPS signal, your handheld can record even more distance while stopped. The distance recorded while standing still is a representation of GPS Drift.
What are Environmental Factors?
Any outside influence on the accuracy of your Garmin handheld is an environmental factor and can cause degraded GPS signal. Environmental factors can range from using GPS downtown in a major city with buildings to trying to record a hike under dense tree canopy. Using your handheld to record GPS in those types of environments blocks the handhelds ability to directly receive GPS signal.
Examples of GPS Drift and Environmental Factors
The image below shows a hiker that stopped for a short amount of time without pausing their activity or powering their device off. You can see that the handheld continued to record track points while they were stopped. This added some additional distance to their hiking activity.
In the image below, the handheld was recording an activity in an area known as an "Urban Canyon". Urban Canyons cause degraded signal due to poor visibility of the horizon and GPS signal refraction caused by windows on buildings. When the signal is very degraded, the GPS accuracy of your handheld goes down and the track of your activity may not show anywhere near the actual path you took.
Improving and Troubleshooting GPS, Distance, and Speed Accuracy
Now that you know what causes track/activity distance to be incorrect, you can take steps to prevent inaccuracies. The troubleshooting below will help you record more accurate tracks.
Be aware that environmental factors cannot be completely overcome, and GPS drift is a natural occurrence.
IMPORTANT: Not all handhelds have all features listed. Refer to your owner's manual for feature compatibility and making changes to your device settings around these features.
Updating Software
Out of date software can lead to irregularities in recorded GPS data. For instructions on updating the software on your specific Garmin model, see - Help with Product Updates.
Changing Recording Interval
Changing how often your handheld records track points can greatly improve distance accuracy, especially when it comes to switchbacks. When viewing a recorded track/activity on the device itself, or in BaseCamp™ or Garmin Connect™ programs, you may notice that it looks like you went straight through switchbacks instead of traveling along them. When the device is set to record at a higher interval, the likelihood of this occurring becomes minimal. The information below discusses different recording methods.
The image below shows one track recorded with an interval of 1 second (the track with the red arrows on it), and another track with an interval of 30 seconds (the plain gray track). The track recorded with 30 second intervals shows less detail than the track with 1 second recording. Because of the longer recording interval, the 30 second track records less distance traveled between track points than the 1 second track.
Enabling WAAS/EGNOS
The WAAS/EGNOS feature improves the position accuracy of GPS by using ground relay systems to correct atmospheric distortion. Enabling WAAS/EGNOS improves the GPS position and elevation accuracy of your handheld. This is typically found on the device under System from the Setup menu. For the GLO device series this feature is always on. For more information, see - What is WAAS?
Enabling Secondary Satellite Systems
Enabling a secondary satellite constellation allows for your handheld to more quickly acquire a satellite fix, and can help maintain satellite connection in degraded signal situations where the environment may be a factor. Inaccurate speed and distance readings may be due to degraded GPS signal, and enabling a secondary satellite constellation may help. This is typically found on the device under System from the Setup menu.
IMPORTANT: Recording more tracking points, enabling WAAS/EGNOS, GLONASS or Galileo will use more battery power on your handheld. Please take this into consideration when making changes to settings, and when planning for a long trip.