GPS location accuracy on Android Smartphone devices

Before we start looking at the detail, it is useful to observe that the term GPS has become ubiquitous with the location of our Smartphone devices, this is, however, only really a small part of the picture.

We all make assumptions about this extremely powerful technology based on our experience with sat-nav software such as google maps, remembering how helpful it has been getting us to the important meeting. I for one have also seen the other side of GPS, using a high spec Smartphone in the city of London can often lead you astray as the reported GPS location is not where you actually are due to your location between several high buildings.

We often have very positive experiences with the GPS accuracy of our devices so there is no need for me to demonstrate them here but to put in to context the potential issues here is an example where a FitBit on an iphone X used to track a straight “there and back” walk across farmland next to a forest recorded inacurate GPS locations on one of the legs.

As with all technologies, there are many subtleties to how location gathering operates, which can lead to mixed experiences and sometimes disappointment with the results achieved without a full understanding of the cause.

For example, the older the Smartphone you use, the less capable (and potentially less accurate) GPS chips within them are. This also stands for cheaper and less well-engineered devices.

How does Your Smartphone find its location?

A small chipset located strategically in the device must communicate with several satellites via a GPS antenna. The antenna is connected via a software driver to the operating system from which the vast majority of smartphone applications including SmartTask obtain their location information.

Location accuracy, therefore, can be impacted by the following:

·         The location / orientation of the Smartphone and other interference factors

·         The number of satellites the phone can see

·         The quality of the GPS chipset and antenna in the Smartphone

·         The implementation of the driver in the operating system

In general, a GPS signal is strongest when a phone is under the clear sky for a reasonable period of time. If the phone can not see the sky, you will have a weak GPS signal and the GPS position reported may not be correct.

Walls, vehicle roofs, tall buildings, mountains, and other obstructions can block line of sight to GPS satellites and in fact cause reflections that further confuse the devices attempts to obtain an accurate location.

GPS accuracy varies depending on the number of visible GPS satellites. Locating all visible satellites can take several minutes, with accuracy gradually increasing over time.

Newer Smartphones have assisted GPS (A-GPS) capabilities which can use Wi-Fi networks and 4G towers to help find the location when GPS is not working; this can help improve and speed accuracy when GPS satellites are present but can also lead to spurious results where no GPS is present i.e. when the phone is in a building.

For these later devices, location detection is most accurate when using a combination of GPS, Wi-Fi, and mobile networks.

Accuracy can vary greatly as the number of satellites in range reduces

Speed of location acquisition is vital for sat-nav type apps, so companies such as Google are implementing tools such as “Google location accuracy”  to help speed up and improve accuracy for these applications. These tools, however, can sometimes contribute to spurious and or confusing results where applications are just attempting to gather the GPS location rather than aligning them to a map as in a sat-nav.

GPS receivers often work best if the GPS signal is kept active as the chipset does not need to keep acquiring the satellites. Location accuracy is particularly challenging where smartphones are continually moving in and out of buildings, so a phone with a slow acquisition rate will perform much worse in these scenarios.

GPS receivers by their nature are looking to locate satellites to determine their location. There are four major satellite networks: GPS (USA), Glonass (Russia), Galileo (Europe) and Beidou (China). Most smartphones use the GPS network, and others can use GPS and also Glonass.

If the Smartphone is Glonass compatible (depending on the smartphone chip), it will connect to a larger number of satellites which should result in  faster and more accurate positioning.

Glonass is available (besides GPS) on several Samsung, Apple or LG smartphones but also on other brands. That’s why these smartphones seem to connect faster to satellites.

Many newer smartphones are also compatible with more satellite networks, but you should not take this for granted and check that each specific device selection fits with your demands for GPS location accuracy.

As with all technologies you should adjust your expectations for location accuracy based on the budget you have, there are many highly accurate GPS solutions available at very high prices and our expectations from our smartphones are often exceeded, this does not, however, take away the underlying issues they might have in challenging environments.  

At best, you might expect to see GPS accuracy down to 3 meters; however, given all of the above this is not a guarantee. In practice, we are often seeing low-cost smartphones reporting GPS locations far away from their actual location as the quality of the GPS location they can detect reduces.

We are often asked, why are my workers phones reporting the incorrect location?

If you take in to account the range of Smartphone hardware, the challenging GPS satellite acquisition environment of moving in and out of buildings and the accuracy of assistive technologies using Wi-Fi and cell towers you can see why unpredictable results can often be seen. We should see GPS and other location technologies for what they are, amazing tools which can help us greatly in certain situations, they work wonderfully given visibility of a clear sky but when circumstances change we should adjust our expectations appropriately.

At SmartTask, we continue to provide the best possible solutions using low-cost technologies so continue to investigate strategies that help our customers get the best value from this extremely powerful technology while staying within its limitations.