7 Reasons Why GPS Positioning Sometimes Inaccurate

by Concox Garin Marketing Manager

GPS Tracking can be very accurate. The satellites used to calculate the position actually use atomic clocks to have the most accurate time possible. However, there are situations in which the GPS position may fail.

①There are not enough satellites

GPS devices usually need to receive signals from at least 7 or 8 satellites to calculate the location within about 10 meters. With fewer satellites that will lead to uncertainty and inaccuracy positioning, and many GPS receivers cannot produce location estimates and will report "GPS signal loss." The GPS receivers generally seek to find and acquire signals from more satellites. For this reason, it is important to calculate the location multiple times in order to find more satellites.

②Initialization and heating

GPS receivers need some time to first acquire signals from satellites. When investigating GPS accuracy, try to allow sufficient time (5 or 10 minutes) for the receiver to acquire the signals from the satellites.

③Cool start

When it is turned on for the first time, the GPS needs to download data from satellites that describe the position and time of all satellites in the system. This helps you acquire signals faster in the future. This initial cold start can take 5 minutes or more.

④Hot start

If you use a GPS device frequently, the device will have up-to-date information about satellite positions and time. In this situation, you must acquire the signals from the satellites in approximately 1-3 minutes.

⑤Assisted GPS start (AGPS)

Mobile phones take advantage of additional location information to initiate GPS. This is called “assisted GPS” or AGPS, and uses information from the cellular towers of the mobile phone network to provide an approximate starting point.

Normally, when AGPS is used, a receiver can acquire satellite signals in 10-30 seconds. After the initial acquisition, the GPS receiver uses only satellite signals. Subsequently, you no longer need help from the mobile phone tower information to update your location estimates.

⑥Signal obstruction

Buildings, trees, tunnels, mountains, clothing and the human body can prevent GPS signals from satellites to reach the receiver. When possible, place a GPS receiver in a place where you have a clear and unobstructed view towards the sky.

In some cases, this can be done by holding the GPS device in a back pocket, in the outer pocket of a backpack or on a handlebar mount. In other cases, obstructions are inevitable, as in the areas of the center where tall buildings block the view of the sky. We also find situations where we are surrounded by dense trees.

⑦Other Error

When the signals from the GPS satellites bounce in the buildings, the GPS receiver can be confused by the additional time it took for the signal to reach it. In these cases, you can observe large sudden errors in the position. There is not much that can be done to reduce the effects of multipath errors. GPS is simply less accurate in canyons, whether the surroundings are buildings or natural formations.

More about GPS Tracking: www.iconcox.com