[Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[Stephen Sacks]

In order to make widely available some wise advice, I'm sending to this 
list a message I received from Neil B.  In addition to Neil's message 
below, I want to mention that Nicolas Cadieux also provided similar 
information, saying I'd have to pay around $1,000 for equipment that 
gives consistently accurate location coordinates.  And thanks, also to 
Falk Huettmann and Bernd Vogelgesang for their replies.


Message from Neil B:

Hello Stephen.
Glad that you're having success. I would like to start off by saying 
that it is best to always reply to the mailing list and not directly to 
the person who submitted the email. Mailing lists work really well in 
that there is a pool of people out there who may be able to offer advice 
or may have an alternate method to solve the problem that may turn out 
to be a better way. On the flip side by maintaining the email chain 
through the mailing list, the follow up emails that provide information 
are stored in the archives which benefits anyone searching the internet 
to have the complete trail of information.

As far as your results they are acceptable for the device you're using. 
GPS in phones are never built to precision survey standards and there is 
no reason for them to be. If you're within 30ft of where the phone 
thinks you should be then you can easily navigate the rest of the way by 
visual sight. High end equipment to achieve sub-inch accuracy is 
probably in the range of thousands of dollars. One thing to keep in mind 
is there is a difference between the accuracy of a device and to what 
level of precision they display. While the app on the phone may display 
8 decimal places of a lat/long coordinate and tell you if you have moved 
a foot, it doesn't help that the coordinate it is displaying is out +/- 
30 feet. The accuracy of a device can also be affected by the 
environment where the device is being operated. In regards to cell 
phones, they use multiple sources to determine location such as GPS, 
cell phone towers, and wifi points to perform the triangulation. Lack of 
line of sight to satellites, signals from cell towers bouncing off of 
surrounding buildings, or someone's wireless router using inaccurate 
position information can all affect the accuracy of what is being 
displayed on your phone.

So the question is how are you determining that the coordinates are 
wrong? If you have information that you trust to be authoritative then 
adjust your points to those values and carry on. I have no advice or 
opinions on inexpensive devices that may help with a more accurate reading.

Please do not respond directly to me. This email account is not actively 
monitored and I don't always have the time to follow up with the emails. 
All the best with your endeavours.

~Neil B.

On Fri, May 15, 2020 at 7:52 PM Stephen Sacks <sacks44 at earthlink.net 
<mailto:sacks44 at earthlink.net>> wrote:

    Hi Neil,

        With your help, I have successfully brought the corners of our
    gardens back from Pennsylvania to the Promenade here in Brooklyn
    Heights, New York.  Thank you.
        At the risk of wearing out my welcome, I'm now asking for more
    advice.  My point features are approximately where they should be
    but not exactly, some points are just a few feet off and some are 10
    or even 30 feet off.  I imported the data trying both EPSG 4326 and
    4269.
        I'm now convinced that the problem is due to (1) my Google Pixel
    3 cellphone, (2) the app I'm using ("Latitude Longitude" published
    by gps-coordinates), and  especially (3) my less-than-steady hands. 
    I capture coordinates by standing at spot, waiting for the blue dot
    to settle, and then touching the blue dot. Often I don't touch the
    screen at exactly the right place.  I tried another app ("GPS
    Coordinates" published by Financept) which is better in that it
    allows me to zoom in, but I'm still not always getting it right.
       I'm thinking now that I need specialized equipment. That is what
    I want to ask you.  Can you recommend some inexpensive device that
    will allow me to simply press a button to record accurately the
    coordinates of the point where I'm standing?  Keep in mind that this
    is a community project with no funding.  I live on Social Security
    and a university pension, but I'm willing to pay something in the
    range of $50 or a bit more.  Do you know of anything at such a
    modest price, or would I have to pay much more?  Or perhaps you know
    of better software for my Android Pixel 3 phone.
          Thanks in advance for any advice you might offer.
                       Steve

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