Can GPS Tracking be Wrong?
GPS tracking technology is used by everyone, everyday and the accuracy is hardly questioned. Is there a chance that your GPS tracker could be reporting the wrong location? Absolutely, but we can show you how to check and confirm that you are seeing correct location data.
GPS Tracking Devices transmit their location to a GPS Tracking server every couple of minutes. Included in the data are three items that will help you determine if your GPS Tracker is wrong. Once you log into your tracking platform, there should be a spot for your to look at the raw GPS messages. This will give you access to additional information that is normally not displayed to the end user. The first item to look for in the raw messages is the number of satellites. This value is telling you how many GPS satellites your tracker could see when the location was calculated. In general, 8 or more satellites should give you an excellent location +/- 5-10ft. Your device can send location data with as little as 4 satellites, but you will jeopardize accuracy because of the lack of visible satellites. This low number of satellites can be normal from time to time depending on the tracker placement, location of your asset (under a bridge, trees, etc), and weather conditions.
The second item to check when validating if your GPS Tracker is wrong would be HDOP or horizontal dilution of precision. In general, you want a value of less than 1. Below is a table showing you how HDOP can effect the location accuracy and cause your gps tracker to give false readings.
| HDOP Value | Rating | Description |
|---|---|---|
| < 1 | Ideal | Highest possible confidence level to be used for applications demanding the highest possible precision at all times. |
| 1-2 | Excellent | At this confidence level, positional measurements are considered accurate enough to meet all but the most sensitive applications. |
| 2-5 | Good | Represents a level that marks the minimum appropriate for making accurate decisions. Positional measurements could be used to make reliable in-route navigation suggestions to the user. |
| 5-10 | Moderate | Positional measurements could be used for calculations, but the fix quality could still be improved. A more open view of the sky is recommended. |
| 10-20 | Fair | Represents a low confidence level. Positional measurements should be discarded or used only to indicate a very rough estimate of the current location. |
| >20 | Poor | At this level, measurements are inaccurate by as much as 300 meters with a 6-meter accurate device (50 DOP × 6 meters) and should be discarded. |
The last item that can cause your GPS tracker to report wrong location information is the date and time. Some times GPS trackers will use a store and forward method which could cause you to see old location date. If a tracking device looses cellular connectivity, it will continue to record your location and store it in memory. Once it regains a cellular connection, it will upload this data to the tracking server. Some times only small chunks of data get uploaded, so when you check your tracking system, it might be an old location. The best way to confirm this is by looking at the timestamp for that location.
As you can see, GPS Trackers can report the wrong information, but this is generally due to a poor install. When installing a GPS tracker, keep in mind that it needs a clear view of the sky to give you the most accurate information.