GPS Accuracy – Tablet or Smartphone GPS vs Real GPS

accuracyandroidgps

I've been reading a lot today about android and iphone devices being used for spatial data collection in the field and it sure seems to be that single purpose devices such as the extremely popular Garmin eTrex are a dead end. Why buy something with a tiny screen, no ability to add custom data collection interfaces, cost-plus base maps, and no picture taking when you can get all that and more for free or very cheap with a tablet/phone?

As near as I can tell so far the only real advantages a real GPS has over these other devices are ruggedness and extended battery life. Unless maybe accuracy? How does the accuracy of a GPS-enabled smart phone or tablet compare with a consumer grade "real" GPS? What about when off-grid? What about cold-start time-to-lock?

Best Answer

There are a huge number of devices to choose from, and it is difficult to broadly say that one family of device are more precise than others. It is better to compare accuracy based on real life tests. However, there are a few things to consider:

  • Chipsets. Dedicated GPS, and Smart Phones use a chipset to actually perform the GPS calculation. The accuracy and capabilities vary. Some chipset's are optimized for urban canyons and are particularly suitable for smart phones (SIRFstar III). Others can track a greater number of satellites concurrently and feature SBAS augmentation. Some cell phone chipsets may outperform those used in dedicated devices. Even some professional grade GPS (Nomad 900G) units ship with less accurate consumer grade chipsets.
  • Antenna. The placement and quality of the antenna effects GPS accuracy. Some dedicated GPS units have external antenna's instead of the internal antenna typical in smartphones. They may also feature an antenna socket to allow an aftermarket antenna to be added.
  • Assisted GPS. It is possible to improve accuracy using data from non-satellite sources. GPS almanac and ephemeris information can be downloaded using a smartphone radio, or uploaded using dedicated GPS software. Smartphone's can also use cellphone towers to aid in positioning. This can improve accuracy and reduce time until first fix.

In summary, it is worth looking at the chipset, antenna specification, and Assisted GPS capabilities to determine the likely performance of the device.

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