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I read in several posts and websites that public GPS signal to smartphones has an accuracy of around 5 m, and that civilian signal accuracy is 100 m. Some other posts mentioned accuracy of c. 2 m and the explanation was that smartphones use also antennas and WiFi to improve accuracy. So I tested my Android by going to a location without any phone signal or WiFi and still my free GPS app showed accuracy of 2 m. So is this reported accuracy wrong? I've plotted it in several GIS options and maps and it seems to be correct. Also has it improved in recent years? I remember back in 2015 this GPS apps gave an accuracy of 6 m. I'm having trouble finding precise information on this topic.

Here's the result of GPStest of 2 different android phones (one 2022 and one 2018) on a geographic marker. 2 other GPS apps showed an estimated accuracy of 2 m.

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    Do you mean that you have ground control points with known accurate coordinates and you measured them with your Android with an error that is less than 2 m?
    – user30184
    Jun 10, 2023 at 18:57
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    Civilian signal hasn't been a thing for many years, I think Clinton demilitarised GPS
    – Ian Turton
    Jun 11, 2023 at 9:58

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tl;dr - Don't trust the "estimated accuracy" value that most GPS apps show you. It's just an estimate coming from the device manufacturer hardware.

The best way to assess accuracy is to find a surveyed benchmark location and use an app like GPSTest to measure the distance between calculated location and your ground truth location (full disclosure - I'm the author of GPSTest). I wrote an article on this:

https://barbeau.medium.com/measuring-gnss-accuracy-on-android-devices-6824492a1389

If you're interested in the general state of recent GNSS developments on Android phones, check out these articles that I wrote on dual frequency GNSS on Android and crowdsourcing the GNSS capabilities of current Android devices:

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  • Agreed - "estimated accuracy" on mobile phones tends to be highly optimistic. But I predict problems when a non-GIS user compares GPS positions (WGS-84 / ITRF2014 current epoch or whatever) with surveyed locations in some other reference frame (for example NAD83).
    – Trams
    Jun 13, 2023 at 1:58
  • Outstanding app. I edited my question with the result of GPSTest. Still puzzled by the high horizontal accuracy (1-2 m)
    – Rodrigues
    Jun 13, 2023 at 21:25
  • What do you mean "high horizontal accuracy"? The Vertical error of 16 to 20M you're seeing is probably because GPSTest gives height relative to Mean Sea Level (MSL), but the Geographic marker gives you height relative to the reference ellipsoid (HAE). If you can see NMEA data for the receiver, the GNGNS sentence includes a "Geoidal separation" parameter.
    – Trams
    Jun 15, 2023 at 1:29
  • Well if you don't really need to know the elevation to a good accuracy (vertical error doesn't matter) and you just need say lat/long, a 1 m accuracy is quite impressive
    – Rodrigues
    Jun 20, 2023 at 23:18

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