[Qgis-user] wishing for accurate lattitude/longitude from a cell phone
Nicolas Cadieux
nicolas.cadieux at archeotec.ca
Mon May 25 11:56:34 PDT 2020
Hi,
Just my grain of salt... I believe the latest move from QGIS to change
to a more recent version of the PROJ library (and to rely more on this
library), is seen as a way to move GIS from a cartographic quality GIS
to a Survey level precision GIS. This is a good move but, as many have
seen on this list, not an easy one. Things seems to have calmed down
recently as people start understanding the error messages and as QGIS
adapted to user demands.
The only way, as I see it, that GARMIN is "privatizing the geography",
as you nicely put it, is by selling map to their map capable units. It
would be nice to have the capability of uploading our own maps to those
units. Apart from that, positions, waypoints and tracks can be
uploaded and download with propitiatory and non propitiatory software.
I believe QGIS had a plugin capable of doing that with multiple consumer
level GPS but I have never used it. Maybe they have been more
aggressive lately? I don't know.
As for the High resolution-precision problem, It's important to remember
that typical consumer level chips are not made to give you more than 2
to 10m precision. This is not because of any effort on there part to
make the units less precise. It's simply because of the way a position
is obtained by these units. Using the same point and shoot method (or
Code Measurements instantaneous position determination), A 100,000,000$
GPS might give you a slightly better position but only because is has a
better internal clock and a better Geoid model. In order to get a more
precise positions, professional GPS units use things like RTK, Dual
frequency, DGPS, but most importantly, they store the satellite
information for later use in a post-processing software. These function
are simply not built or used in phones or consumer GPS devices. Any unit
using instantaneous position determination will always be plague by
orbital errors, satellite cloak errors, Ionospheric and troposphere
errors, multipath and receiver noise... The only thing they can change
is the receiver clock and the antenna. A technique called PPP, or
Precise Point Positioning is a technique were one uses a single GPS unit
to find precise position after a long observation. Again, the most we
can do with consumer lever gps is to average out positions. This is not
PPP which uses the rinex files stored in the unit, correct for clock and
ephemerides...
If you are interested in bringing High precision GPS to the table, I
suggest RTKlib (http://www.rtklib.com/) for post processing. Again, you
will need a deceive capable of storing the satellite information if you
want to do this. A plugin from RTKlib to QGIS could be made it guess.
That would be nice.
Cheers!
Nicolas
On 2020-05-25 1:47 p.m., Falk Huettmann wrote:
> Dear List,
> I think these GPS high resolution suggestions are great;
> thanks.
>
> But my real interest/question here is, how can we bring it home to QGIS ?
>
> I see GARMIN essentially trying to sell and impose on us their GIS system,
> same applies to OpenStreet Maps etc etc. So they try to privatize
> geography and public space and information,
> which I am mostly opposed to.
>
> Instead, I wonder how we can use QGIS and release the commercial
> data into Open Source and public use ?
> That's for HIGH RESOLUTION data discussed here.
>
> Thanks for such questions and solutions.
>
> Very best
> Falk Huettmann PhD, Professor
> Uni of Alaska Fairbanks
>
>
> On Mon, May 25, 2020 at 9:41 AM Kirk Schmidt <kirk at nortekresources.com
> <mailto:kirk at nortekresources.com>> wrote:
>
> Hi List:
>
> In my experience, the key is writing output in rinex format so
> that the rover data can be corrected either using PPP if you can
> collect your GPS data over and extended period of time or use
> pre-existing (or self deployed) base station over a know
> coordinate to provide correction data. Most consumer grade units
> output the final position solution, not detailed satellite data
> which is required for followup processing.
>
> Kirk Schmidt
>
> On 5/25/2020 2:31 PM, chris hermansen wrote:
>> Martin and list,
>>
>> To me, in general, I think I would try to go with a Raspberry Pi
>> based solution. The hardware isn't all that expensive and the
>> easy ability to do stuff directly with the output of the device
>> in Python or some other programming language seems to be
>> preferable to messing around with Android or iOS applications.
>>
>> One of many articles that may be of interest
>> https://learn.adafruit.com/adafruit-ultimate-gps-on-the-raspberry-pi?view=all
>>
>> On Mon, May 25, 2020 at 9:25 AM Martin Weis
>> <martin.weis.newsadress at gmx.de
>> <mailto:martin.weis.newsadress at gmx.de>> wrote:
>>
>> Dear list,
>>
>> I would like to add some things here, since I am trying to
>> use RTK GPS
>> in the field with mobile devices.
>>
>> > 1) Accuracy of GPS Devices
>>
>> RTK GPS or any more precice GPS technology will be external,
>> you cannot
>> get around the missing measurements and lack of algorithms in
>> consumer
>> grade chips.
>>
>> Then it depends on the capabilities of the device to receive
>> satellites
>> of all systems (one or multiple frequencies/signals) and be
>> able to
>> apply correction data (a question of algorithms). For better
>> equipment
>> the prices rise quickly.
>>
>> There are some low cost devices evolving, a new chip was recently
>> announced: Skytraq PX1122R for about $100. Could be tested
>> with a break
>> out board and antenna, e.g. see board at navspark shop. The
>> module even
>> supports PPP, which might be especially interesting where
>> mobile network
>> is not available.
>> https://navspark.mybigcommerce.com/px1122r-evb-px1122r-multi-band-quad-gnss-rtk-evaluation-board/
>>
>> Other low cost solution were mentioned (emlid/REACH,
>> Catalyst, etc).
>>
>>
>> Am 23.05.20 um 21:51 schrieb Michael.Dodd:
>> > One app that claims to do a lot of what high precions gps
>> does is> Mobile Topographer Free – Apps on Google Play
>>
>> > 2) Software
>>
>> On Android I was able to get the external signal into the
>> system, you
>> need the app "Bluetoth GPS" (or similar) or a USB2serial +
>> app (better
>> avoid tiny plugs and large cables during field work).
>> Additionally you
>> need to override the internal GPS position with the Blue GPS
>> App in the
>> developer settings (mock provider).
>>
>> My impression was, that most Android applications target the
>> accuracy of
>> the device only, so e.g.
>>
>> * you cannot zoom to cm-levels, only ~100m
>> * not many proper GIS Apps are available, most are expensive
>> * Tracking usually does not rely on cm-grade positions, so
>> the apps are
>> not made for it
>>
>> One particular thing is, that with high accuracy of the
>> signal, an
>> internal computation in single precision float will not
>> suffice (all
>> computations must be in double precision), and you may end up
>> with a cut
>> off of the last position digits, e.g. if you have 8 digits, 4
>> before and
>> 4 after the decimal separator (e.g. in DDMM.MMMM format),
>> then you end
>> up with coordinates cut down to 2-3 decimeters in the real world
>> (typical GPS mouse output, not so uncommon).
>>
>> So, looking into that aspect may be required, and only few
>> Apps may
>> implement that (e.g. expensive "surveyor" apps for
>> professionals? did
>> not test).
>> BTW, sponsoring the double accuracy implementation for QField is
>> welcome, as mentioned ot the webpage. It is already a very
>> usable and
>> FLOSS GIS solution for the field, especially useful if you
>> have a QGIS
>> workflow already ;)
>>
>> Finding proper solutions and recommendations still required...
>>
>>
>>
>> >
>> ------------------------------------------------------------------------
>> > *From:* Qgis-user <qgis-user-bounces at lists.osgeo.org
>> <mailto:qgis-user-bounces at lists.osgeo.org>> on behalf of
>> > j.huber at post-ist-da.de <mailto:j.huber at post-ist-da.de>
>> <j.huber at post-ist-da.de <mailto:j.huber at post-ist-da.de>>
>> > *Sent:* 23 May 2020 20:35
>> > *To:* qgis-user at lists.osgeo.org
>> <mailto:qgis-user at lists.osgeo.org> <qgis-user at lists.osgeo.org
>> <mailto:qgis-user at lists.osgeo.org>>
>> > *Subject:* Re: [Qgis-user] wishing for accurate
>> lattitude/longitude from
>> > a cell phone
>> >
>> >
>> > Hi Steve,
>> >
>> > I think there are two different aspects to your question:
>> > 1) Accuracy of GPS Devices
>> > I agree with others that you can't expect a better accuracy
>> than the 10
>> > to 30 feet you observed with a smartphone or a simple
>> handheld GPS. This
>> > might improve by averaging, but this takes time. Survey
>> grade GPS
>> > devices are very expensive. It is possible to get good
>> modules and
>> > antennas as components, but building a complete GNSS system
>> requires
>> > time and skill. This would reduce cost, but only to several
>> hundred
>> > instead of several thousand dollars, so this is no option
>> in your case.
>> > Besides, you will still need a correction data service
>> (usually costly)
>> > or use two receivers (rover and base).
>> > So you probably have to stick with your phone, which is
>> more flexible
>> > regarding the software than a handheld GPS.
>> >
>> > 2) Software
>> > The accuracy of the recorded position should not depend on
>> where you tap
>> > the screen - a good app should allow to record the current
>> GPS position.
>> > I am using Locus Map (Asamm Software) for a while now, it
>> works quite
>> > well, although it does not allow position averaging. There
>> is a free
>> > version, you could try that first.
>> >
>> > Regards,
>> > Jochen
>> >
>> > Am 22.05.20 um 20:54 schrieb 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>
>> >> <mailto: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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>>
>> --
>> Chris Hermansen · clhermansen "at" gmail "dot" com
>>
>> C'est ma façon de parler.
>>
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> --
> Kirk Schmidt, MScF, BScF, RPF
> General Manager
> Nortek Resource Solutions Inc.
> RR # 1
> Thorburn, NS
> B0K 1W0
> Tel (902) 922.3607
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