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<p>Hi List:<br>
</p>
<p>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.<br>
</p>
<p> Kirk Schmidt<br>
</p>
<div class="moz-cite-prefix">On 5/25/2020 2:31 PM, chris hermansen
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CACc2_699zC0sR4MCi1RGtU=75GxYXedYYga5BcUTt0GkQqpsgw@mail.gmail.com">
<div dir="ltr">
<div>Martin and list,</div>
<div><br>
</div>
<div>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.</div>
<div><br>
</div>
<div>One of many articles that may be of interest <a
href="https://learn.adafruit.com/adafruit-ultimate-gps-on-the-raspberry-pi?view=all"
moz-do-not-send="true">https://learn.adafruit.com/adafruit-ultimate-gps-on-the-raspberry-pi?view=all</a></div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Mon, May 25, 2020 at 9:25
AM Martin Weis <<a
href="mailto:martin.weis.newsadress@gmx.de"
moz-do-not-send="true">martin.weis.newsadress@gmx.de</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote">Dear list,<br>
<br>
I would like to add some things here, since I am trying to use
RTK GPS<br>
in the field with mobile devices.<br>
<br>
> 1) Accuracy of GPS Devices<br>
<br>
RTK GPS or any more precice GPS technology will be external,
you cannot<br>
get around the missing measurements and lack of algorithms in
consumer<br>
grade chips.<br>
<br>
Then it depends on the capabilities of the device to receive
satellites<br>
of all systems (one or multiple frequencies/signals) and be
able to<br>
apply correction data (a question of algorithms). For better
equipment<br>
the prices rise quickly.<br>
<br>
There are some low cost devices evolving, a new chip was
recently<br>
announced: Skytraq PX1122R for about $100. Could be tested
with a break<br>
out board and antenna, e.g. see board at navspark shop. The
module even<br>
supports PPP, which might be especially interesting where
mobile network<br>
is not available.<br>
<a
href="https://navspark.mybigcommerce.com/px1122r-evb-px1122r-multi-band-quad-gnss-rtk-evaluation-board/"
rel="noreferrer" target="_blank" moz-do-not-send="true">https://navspark.mybigcommerce.com/px1122r-evb-px1122r-multi-band-quad-gnss-rtk-evaluation-board/</a><br>
<br>
Other low cost solution were mentioned (emlid/REACH, Catalyst,
etc).<br>
<br>
<br>
Am 23.05.20 um 21:51 schrieb Michael.Dodd:<br>
> One app that claims to do a lot of what high precions gps
does is> Mobile Topographer Free – Apps on Google Play<br>
<br>
> 2) Software<br>
<br>
On Android I was able to get the external signal into the
system, you<br>
need the app "Bluetoth GPS" (or similar) or a USB2serial + app
(better<br>
avoid tiny plugs and large cables during field work).
Additionally you<br>
need to override the internal GPS position with the Blue GPS
App in the<br>
developer settings (mock provider).<br>
<br>
My impression was, that most Android applications target the
accuracy of<br>
the device only, so e.g.<br>
<br>
* you cannot zoom to cm-levels, only ~100m<br>
* not many proper GIS Apps are available, most are expensive<br>
* Tracking usually does not rely on cm-grade positions, so the
apps are<br>
not made for it<br>
<br>
One particular thing is, that with high accuracy of the
signal, an<br>
internal computation in single precision float will not
suffice (all<br>
computations must be in double precision), and you may end up
with a cut<br>
off of the last position digits, e.g. if you have 8 digits, 4
before and<br>
4 after the decimal separator (e.g. in DDMM.MMMM format), then
you end<br>
up with coordinates cut down to 2-3 decimeters in the real
world<br>
(typical GPS mouse output, not so uncommon).<br>
<br>
So, looking into that aspect may be required, and only few
Apps may<br>
implement that (e.g. expensive "surveyor" apps for
professionals? did<br>
not test).<br>
BTW, sponsoring the double accuracy implementation for QField
is<br>
welcome, as mentioned ot the webpage. It is already a very
usable and<br>
FLOSS GIS solution for the field, especially useful if you
have a QGIS<br>
workflow already ;)<br>
<br>
Finding proper solutions and recommendations still required...<br>
<br>
<br>
<br>
>
------------------------------------------------------------------------<br>
> *From:* Qgis-user <<a
href="mailto:qgis-user-bounces@lists.osgeo.org"
target="_blank" moz-do-not-send="true">qgis-user-bounces@lists.osgeo.org</a>>
on behalf of<br>
> <a href="mailto:j.huber@post-ist-da.de" target="_blank"
moz-do-not-send="true">j.huber@post-ist-da.de</a> <<a
href="mailto:j.huber@post-ist-da.de" target="_blank"
moz-do-not-send="true">j.huber@post-ist-da.de</a>><br>
> *Sent:* 23 May 2020 20:35<br>
> *To:* <a href="mailto:qgis-user@lists.osgeo.org"
target="_blank" moz-do-not-send="true">qgis-user@lists.osgeo.org</a>
<<a href="mailto:qgis-user@lists.osgeo.org" target="_blank"
moz-do-not-send="true">qgis-user@lists.osgeo.org</a>><br>
> *Subject:* Re: [Qgis-user] wishing for accurate
lattitude/longitude from<br>
> a cell phone<br>
> <br>
><br>
> Hi Steve,<br>
><br>
> I think there are two different aspects to your question:<br>
> 1) Accuracy of GPS Devices<br>
> I agree with others that you can't expect a better
accuracy than the 10<br>
> to 30 feet you observed with a smartphone or a simple
handheld GPS. This<br>
> might improve by averaging, but this takes time. Survey
grade GPS<br>
> devices are very expensive. It is possible to get good
modules and<br>
> antennas as components, but building a complete GNSS
system requires<br>
> time and skill. This would reduce cost, but only to
several hundred<br>
> instead of several thousand dollars, so this is no option
in your case.<br>
> Besides, you will still need a correction data service
(usually costly)<br>
> or use two receivers (rover and base).<br>
> So you probably have to stick with your phone, which is
more flexible<br>
> regarding the software than a handheld GPS.<br>
><br>
> 2) Software<br>
> The accuracy of the recorded position should not depend
on where you tap<br>
> the screen - a good app should allow to record the
current GPS position.<br>
> I am using Locus Map (Asamm Software) for a while now, it
works quite<br>
> well, although it does not allow position averaging.
There is a free<br>
> version, you could try that first.<br>
><br>
> Regards,<br>
> Jochen<br>
><br>
> Am 22.05.20 um 20:54 schrieb Stephen Sacks:<br>
>><br>
>> In order to make widely available some wise advice,
I'm sending to<br>
>> this list a message I received from Neil B. In
addition to Neil's<br>
>> message below, I want to mention that Nicolas Cadieux
also provided<br>
>> similar information, saying I'd have to pay around
$1,000 for<br>
>> equipment that gives consistently accurate location
coordinates. And<br>
>> thanks, also to Falk Huettmann and Bernd Vogelgesang
for their replies. <br>
>><br>
>><br>
>> Message from Neil B:<br>
>><br>
>> Hello Stephen.<br>
>> Glad that you're having success. I would like to
start off by saying<br>
>> that it is best to always reply to the mailing list
and not directly<br>
>> to the person who submitted the email. Mailing lists
work really well<br>
>> in that there is a pool of people out there who may
be able to offer<br>
>> advice or may have an alternate method to solve the
problem that may<br>
>> turn out to be a better way. On the flip side by
maintaining the email<br>
>> chain through the mailing list, the follow up emails
that provide<br>
>> information are stored in the archives which benefits
anyone searching<br>
>> the internet to have the complete trail of
information.<br>
>><br>
>> As far as your results they are acceptable for the
device you're<br>
>> using. GPS in phones are never built to precision
survey standards and<br>
>> there is no reason for them to be. If you're within
30ft of where the<br>
>> phone thinks you should be then you can easily
navigate the rest of<br>
>> the way by visual sight. High end equipment to
achieve sub-inch<br>
>> accuracy is probably in the range of thousands of
dollars. One thing<br>
>> to keep in mind is there is a difference between the
accuracy of a<br>
>> device and to what level of precision they display.
While the app on<br>
>> the phone may display 8 decimal places of a lat/long
coordinate and<br>
>> tell you if you have moved a foot, it doesn't help
that the coordinate<br>
>> it is displaying is out +/- 30 feet. The accuracy of
a device can also<br>
>> be affected by the environment where the device is
being operated. In<br>
>> regards to cell phones, they use multiple sources to
determine<br>
>> location such as GPS, cell phone towers, and wifi
points to perform<br>
>> the triangulation. Lack of line of sight to
satellites, signals from<br>
>> cell towers bouncing off of surrounding buildings, or
someone's<br>
>> wireless router using inaccurate position information
can all affect<br>
>> the accuracy of what is being displayed on your
phone.<br>
>><br>
>> So the question is how are you determining that the
coordinates are<br>
>> wrong? If you have information that you trust to be
authoritative then<br>
>> adjust your points to those values and carry on. I
have no advice or<br>
>> opinions on inexpensive devices that may help with a
more accurate<br>
>> reading.<br>
>><br>
>> Please do not respond directly to me. This email
account is not<br>
>> actively monitored and I don't always have the time
to follow up with<br>
>> the emails. All the best with your endeavours.<br>
>><br>
>> ~Neil B.<br>
>><br>
>> On Fri, May 15, 2020 at 7:52 PM Stephen Sacks <<a
href="mailto:sacks44@earthlink.net" target="_blank"
moz-do-not-send="true">sacks44@earthlink.net</a><br>
>> <mailto:<a href="mailto:sacks44@earthlink.net"
target="_blank" moz-do-not-send="true">sacks44@earthlink.net</a>>>
wrote:<br>
>><br>
>> Hi Neil,<br>
>><br>
>> With your help, I have successfully brought
the corners of our<br>
>> gardens back from Pennsylvania to the Promenade
here in Brooklyn<br>
>> Heights, New York. Thank you.<br>
>> At the risk of wearing out my welcome, I'm now
asking for more<br>
>> advice. My point features are approximately
where they should be<br>
>> but not exactly, some points are just a few feet
off and some are<br>
>> 10 or even 30 feet off. I imported the data
trying both EPSG 4326<br>
>> and 4269.<br>
>> I'm now convinced that the problem is due to
(1) my Google<br>
>> Pixel 3 cellphone, (2) the app I'm using
("Latitude Longitude"<br>
>> published by gps-coordinates), and especially
(3) my<br>
>> less-than-steady hands. I capture coordinates by
standing at<br>
>> spot, waiting for the blue dot to settle, and
then touching the<br>
>> blue dot. Often I don't touch the screen at
exactly the right<br>
>> place. I tried another app ("GPS Coordinates"
published by<br>
>> Financept) which is better in that it allows me
to zoom in, but<br>
>> I'm still not always getting it right.<br>
>> I'm thinking now that I need specialized
equipment. That is<br>
>> what I want to ask you. Can you recommend some
inexpensive device<br>
>> that will allow me to simply press a button to
record accurately<br>
>> the coordinates of the point where I'm standing?
Keep in mind<br>
>> that this is a community project with no
funding. I live on<br>
>> Social Security and a university pension, but I'm
willing to pay<br>
>> something in the range of $50 or a bit more. Do
you know of<br>
>> anything at such a modest price, or would I have
to pay much<br>
>> more? Or perhaps you know of better software for
my Android Pixel<br>
>> 3 phone.<br>
>> Thanks in advance for any advice you might
offer.<br>
>> Steve<br>
>> <br>
>><br>
>><br>
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<br>
<br>
-- <br>
<div dir="ltr" class="gmail_signature">
<div dir="ltr">Chris Hermansen · clhermansen "at" gmail "dot"
com<br>
<br>
C'est ma façon de parler.</div>
</div>
<br>
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<pre class="moz-quote-pre" wrap="">_______________________________________________
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</blockquote>
<pre class="moz-signature" cols="72">--
Kirk Schmidt, MScF, BScF, RPF
General Manager
Nortek Resource Solutions Inc.
RR # 1
Thorburn, NS
B0K 1W0
Tel (902) 922.3607
Email: <a class="moz-txt-link-abbreviated" href="mailto:kirk@nortekresources.com">kirk@nortekresources.com</a>
Web: <a class="moz-txt-link-abbreviated" href="http://www.nortekresources.com">www.nortekresources.com</a></pre>
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