GPS drift and environmental factors can impact the accuracy of locations and activities recorded by your iGS620.

The information in this article will help you understand and reduce the impacts of GPS drift and environmental factors. 

GPS Drift and Environmental Factors

What is GPS Drift?

GPS drift, in the most practical sense, is the difference between your actual location and the location recorded by a GPS receiver.

Consumer grade GPS receivers (such as the ones iGPSPORT makes) are not 100% accurate, this will usually cause a difference between your actual location and your recorded location. 

The GPS location accuracy of iGPSPORT is around 3 meters (10 feet), 95% of the time.

This means, at any given time, your iGS620 / iGS618 will save your location within 3 meters of your actual location.

If your device is recording a GPS location every second and you do not pause an activity while standing still, your iGS620 can record up to 180 meters (590 ft) in just 1 minute.

When in an area with degraded GPS signal, your device 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 iGS620 is an environmental factor and can cause degraded GPS signal.

Environmental factors can range from using GPS downtown in a major city to running in a big group of people to trying to record a hike under a dense tree canopy.

Using your iGS620 to record GPS in those types of environments blocks the device's ability to directly receive GPS signal.

You can think of environmental factors as things that interrupt the signal path of a GPS satellite to your iGS620. 

Examples of GPS Drift and Environmental Factors

Example 1: GPS Indoors

The image below shows a track recorded by a GPS handheld device that was turned on and recording in a building. This illustrates what it would look like if you were to record GPS while standing still in a highly degraded GPS environment. 

Example 2: Stopping Without Pausing During an Activity

This images shows a hiker that stopped for a short amount of time without pausing their activity. You can see that the watch continued to record GPS points while the person was stopped. This added some additional distance to their hiking activity.

Example 3: GPS Distortion Caused by Environmental Factors

In the example below, the device 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 taller buildings. When signal is very degraded, the GPS accuracy of your device goes down and the track of your activity may not show anywhere near the actual path you took. 

Troubleshooting GPS Distance and Accuracy

Now that you know what causes activity distance to be incorrect, you can take steps to prevent inaccuracies.

The information below will help you record more accurate tracks.

Be aware that environmental factors cannot be completely overcome, and GPS drift is a natural occurrence.

1. Reduce Environmental Factors

The first step to recording accurate GPS data is to reduce distortion and degradation caused by environmental factors. GPS works best when there are no obstructions above 15 degrees over the horizon. Avoid the following when recording activities:

• Tall buildings
• Dense forest or canopy
• Canyons
• Using GPS in a dense group of people
• Using GPS indoors
• Using GPS under water 

2. Soak the GPS

When a watch initially displays that it is GPS ready, it means that the watch has picked up the minimum amount of satellites needed to get your location.

Soaking GPS is practice of allowing your watch additional time to communicate with satellites before you start moving for your activity.

This practice allows for your watch to communicate to additional satellites, creating a stronger bond and helping to reduce degradation of GPS signal.  

Soaking GPS

1. Select an activity 
2. Wait for the GPS Ready message or GPS Indicator to turn green
3. Wait 2-5 minutes before you start the timer for your activity

3. Turn on Auto Pause

Recording GPS while stopped is one of the biggest contributors to inaccurate distance in an activity. Setting your iGS620 / iGS618 to pause when you are stopped, can greatly reduce the amount of additional distance recorded. 

4. Equip a speed sensor

When using a speed sensor, GPS will still be recorded for your activity, but your distance will be based on the measurement of your speed sensor. 

Speed Sensor

Speed sensors use the size of your bike's wheel and the number of rotations it makes during a cycling activity to determine your distance.The speed at which your wheel rotates will determine speed. 

For more details ,see the article Why should I equip a speed sensor