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<p>Hi,</p>
<p>I see lot's of people are interested in this topic. I recommend
reading this basic Guide on GPS Positioning. <a
href="https://www.rncan.gc.ca/sites/www.nrcan.gc.ca/files/earthsciences/pdf/GPS_Guide_e/GPS_Guide_e.pdf">https://www.rncan.gc.ca/sites/www.nrcan.gc.ca/files/earthsciences/pdf/GPS_Guide_e/GPS_Guide_e.pdf</a></p>
<p>It's an older guide, (before waas, glonas, and even before GPS
clock signal was "liberated".) but it will explain different types
of GPS, how positions are found (code positioning vs carrier
positioning), source of errors... Have fun reading. After that,
you will understand why we get the result we get with a consumer
(single point code positioning) GPS.</p>
<p>So basically, after this guide, the GPS full constellation was
finished, single point GPS went from a 100m accuracy to 10m
because the US stopped reducing the clock precision, WAAS was
introduced, other GNSS constellations were put up. <br>
</p>
<p>Nicolas <br>
</p>
<div class="moz-cite-prefix">On 2020-05-23 4:43 p.m., Madry, Scott
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:3AD1299C-6B83-41A8-8EDB-C0C98300C91B@ad.unc.edu">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
Hello all. Regarding GNSS precision, I also find useful the
Trimble online GNSS planning website:
<div class=""><br class="">
</div>
<div class=""><a href="https://www.gnssplanning.com/#/settings"
class="" moz-do-not-send="true">https://www.gnssplanning.com/#/settings</a></div>
<div class=""><br class="">
</div>
<div class="">Which lets you pick a location and timeframe, and it
will show you the real time status of each GNSS constellation,
and lets you pick some or all. It will compute your DOP, number
of satellites from each constellation in view, a sky plot, and
also ionospheric index, TEC (Total Electron Content), and
scintillation. This is all useful for planning when would be the
optimum time to do your field measurements. A good teaching tool
for GNSS as well.</div>
<div class=""><br class="">
</div>
<div class="">My experience with GNSS is that you do get what you
pay for. A ~$200 Garmin with WAAS gives us reliable ~2meters,
cell phones ~10 meters, and you can pay for ~ cm with the
surveying class kinematic systems. It all depends on what you
are measuring and what precision you require. </div>
<div class=""><br class="">
</div>
<div class="">Scott Madry<br class="">
<div><br class="">
<blockquote type="cite" class="">
<div class="">On May 23, 2020, at 3:53 PM, Mike Hyslop <<a
href="mailto:mdhyslop@mtu.edu" class=""
moz-do-not-send="true">mdhyslop@mtu.edu</a>> wrote:</div>
<br class="Apple-interchange-newline">
<div class="">
<div dir="ltr" class="">
<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif;font-size:large">
If you don't want to attempt to engineer your own GNSS
hardware + software, you may want to check out the Bad
Elf GNSS Surveyor. Yes, it's in the neighborhood of
$500 US, but gives relatively consistent positions
within about 1 meter with averaging, its data can be
differentially corrected using the RTKLIB open-source
software, and if you are working in an area with cell
service, it can receive real-time corrections via
NTRIP networks if this is available in your area (it
is here in Michigan). Some Googling will turn up
tutorials. I have done some simple comparisons with
Trimble hardware and have been pleased with the
results.</div>
<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif;font-size:large">
<br class="">
</div>
<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif;font-size:large">
Best,</div>
<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif;font-size:large">
Mike</div>
</div>
<br class="">
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Sat, May 23, 2020
at 3:45 PM <<a href="mailto:j.huber@post-ist-da.de"
class="" moz-do-not-send="true">j.huber@post-ist-da.de</a>>
wrote:<br class="">
</div>
<blockquote class="gmail_quote" style="margin:0px 0px
0px 0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div class="">
<div class="">Hi Nicolas,</div>
<div class=""><br class="">
</div>
<div class="">there are several potentially accurate
GNSS modules available, even sensitive choke ring
antennas aren't that expensive. What's time
consuming and difficult is building a whole
functioning system (integration and software).<br
class="">
</div>
<div class="">This would be a great university
project - develop an open source GNSS system based
on relatively unexpensive components. It should be
possible to get the cost down from over a thousand
to several hundred euro. This could also be the
basis for a "free" correction data service built
on private reference stations. Just dreaming...</div>
<div class=""><br class="">
</div>
<div class="">I agree that for precision, "old
school" technology is often better and cheaper,
although it requires more effort than simply
pushing a button.<br class="">
</div>
<div class=""><br class="">
</div>
<div class="">Regards<br class="">
Jochen<br class="">
</div>
<div class=""><br class="">
</div>
<div class="">Am 23.05.20 um 20:21 schrieb Nicolas
Cadieux:<br class="">
</div>
<blockquote type="cite" class="">
<div class="">Hi,</div>
<div class=""><br class="">
</div>
<div class="">I looked at the page.It looks like a
neat project! Buy time you buy a case,
antenna... (I don’t think they come with on),
your back into the price range of a forestry
grade survey GPS unit. I think the Emild single
band gps (<a href="https://emlid.com/reachrs/"
target="_blank" class=""
moz-do-not-send="true">https://emlid.com/reachrs/ </a>) is
probably a better choice unless you really want
to make this a learning project. But if I
understand you are really on a shoe string
budget.</div>
<div class=""><br class="">
</div>
<div class="">None of these Gps, by the way, would
beat and old theodolite... if you can establish
or find a good gps position (look for the city
or state geomatics services) or survey point, a
théodolite would give you survey grade
positions. City have these points on every few
blocks. You may be able to find A theodolite
for free. A second hand TotalStation could be
better but that will be more difficult to find
in those price ranges (Shoe string). You can
also rent equipment or find a college that would
take this up as a teaching opportunity.</div>
<div class=""><br class="">
</div>
<div class="">Have fun!</div>
<div class=""><br class="">
<div dir="ltr" class="">Nicolas Cadieux
<div class="">Ça va bien aller!</div>
</div>
<div dir="ltr" class=""><br class="">
<blockquote type="cite" class="">Le 23 mai
2020 à 13:52, Bernd Vogelgesang <a
href="mailto:bernd.vogelgesang@gmx.de"
target="_blank" class=""
moz-do-not-send="true">
<bernd.vogelgesang@gmx.de></a> a
écrit :<br class="">
<br class="">
</blockquote>
</div>
<blockquote type="cite" class="">
<div dir="ltr" class="">
<p class="">Unfortunately, the Forest
Service Website went offline (maybe this
thread caused so much traffic that it
broke down? ;) )<br class="">
</p>
<p class="">I'm also desperately searching
for an affordable way to have at least
some decent accuracy. I do not need
submeter, but it would be fantastic if it
was possible to achieve meter accuracy.<br
class="">
I gave up on that Garmin stuff. They might
be accurate, but I have no chance to
control this until I return home and put
the recorded data on screen over an aerial
image. Those screens are a joke, and the
business logic that prevents me to put
reasonable aerial imagery on the device
without paying a fortune is apita. Maybe
this improved cause I last checked 5 years
ago.</p>
<p class="">Mobile phones at least in my
case seem to get worse. My Motorola from
2016 had an accuracy of less than 4
meters, most of the time less than 2.<br
class="">
Now I bought a Huawei 30 pro cause of the
camera (my first phone with nice
pictures!), but the accuracy is a
nightmare. The position is jumping around
like a dog on rabies.<br class="">
I also bought a bluetooth device (Navilock
BT-821G) two years ago. This is much
better than the phones GPS, tho it only
receives 20 satellites maximum (The phone
claims to receive some 40). But also this
device sometimes, when walking a transect,
is constantly 5 meters off the track for
several several minutes.</p>
<p class="">As apps averaging the positions
were mentioned: Does anyone have a
recommendation on such apps (for Android)?
I found some, but the usability was not
that great, and some even didn't enhance
anything.</p>
<p class="">Furthermore, I stumble upon an
article about a module with u-blox chip.
<a
href="https://www.sparkfun.com/products/16481"
target="_blank" class=""
moz-do-not-send="true">https://www.sparkfun.com/products/16481</a><br
class="">
Does anyone have any experience with
modules like this and what else is needed?
The description of all the stuff leaves me
a bit puzzled.</p>
<p class="">Cheers,</p>
<p class="">Bernd<br class="">
</p>
<div class="">On 23.05.20 18:17,
Michael.Dodd wrote:<br class="">
</div>
<blockquote type="cite" class="">
<div class=""><a
href="https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/j.2041-210X.2011.00118.x"
id="gmail-m_-4099059542455145880LPlnk857492" target="_blank" class=""
moz-do-not-send="true">https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/j.2041-210X.2011.00118.x</a>
I did this quite a few years ago but in
the graph in supplimentary material it
shows how the accuracy of one consumer
grade gps varies over time (at a fixed
point). At the time I also did a lot
more measurements using mobile phones
and consumer grade units on a grid of
points in the field, that was not
published but basically the phones were
often as good as if not better than the
consumer grade gps units especially when
using certain apps to average points.<br
class="">
</div>
<div
id="gmail-m_-4099059542455145880LPBorder_GTaHR0cHM6Ly9iZXNqb3VybmFscy5vbmxpbmVsaWJyYXJ5LndpbGV5LmNvbS9kb2kvZnVsbC8xMC4xMTExL2ouMjA0MS0yMTBYLjIwMTEuMDAxMTgueA.."
class="">
<table
id="gmail-m_-4099059542455145880LPContainer618713"
class="">
<tbody class="">
<tr class="">
<td class="">
<div
id="gmail-m_-4099059542455145880LPImageContainer618713"
class=""><a
id="gmail-m_-4099059542455145880LPImageAnchor618713"
href="https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/j.2041-210X.2011.00118.x"
target="_blank" class=""
moz-do-not-send="true"><img
id="gmail-m_-4099059542455145880LPThumbnailImageId618713" alt=""
class=""
moz-do-not-send="true"
width="123" height="160"></a></div>
</td>
<td class="">
<div
id="gmail-m_-4099059542455145880LPTitle618713"
class=""><a
id="gmail-m_-4099059542455145880LPUrlAnchor618713"
href="https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/j.2041-210X.2011.00118.x"
target="_blank" class=""
moz-do-not-send="true">Where
are my quadrats? Positional
accuracy in fieldwork - Dodd
- 2011 - Methods in Ecology
and Evolution - Wiley Online
Library</a></div>
<div
id="gmail-m_-4099059542455145880LPDescription618713"
class="">Introduction. There
has been much written about
sampling design, spatial scale
and the need for permanent
plots in ecological long‐term
monitoring, for example, the
paper on spatial scaling in
ecology has been cited over
1500 times, but one frequently
ignored issue, intimately
associated with sampling
design, scale and permanence
of plots, is how to locate
positions accurately.</div>
<div
id="gmail-m_-4099059542455145880LPMetadata618713"
class=""><a
href="http://besjournals.onlinelibrary.wiley.com/"
target="_blank" class=""
moz-do-not-send="true">besjournals.onlinelibrary.wiley.com</a></div>
</td>
</tr>
</tbody>
</table>
</div>
<br class="">
<hr class="">
<div
id="gmail-m_-4099059542455145880divRplyFwdMsg"
dir="ltr" class=""><b class="">From:</b>
Qgis-user
<a
href="mailto:qgis-user-bounces@lists.osgeo.org"
target="_blank" class=""
moz-do-not-send="true"><qgis-user-bounces@lists.osgeo.org></a>
on behalf of Nicolas Cadieux
<a
href="mailto:nicolas.cadieux@archeotec.ca"
target="_blank" class=""
moz-do-not-send="true"><nicolas.cadieux@archeotec.ca></a><br
class="">
<b class="">Sent:</b> 23 May 2020 16:34<br
class="">
<b class="">To:</b> Randal Hale <a
href="mailto:rjhale@northrivergeographic.com"
target="_blank" class=""
moz-do-not-send="true">
<rjhale@northrivergeographic.com></a><br class="">
<b class="">Cc:</b> <a
href="mailto:qgis-user@lists.osgeo.org"
target="_blank" class=""
moz-do-not-send="true">
qgis-user@lists.osgeo.org</a> <a
href="mailto:qgis-user@lists.osgeo.org"
target="_blank" class=""
moz-do-not-send="true">
<qgis-user@lists.osgeo.org></a><br
class="">
<b class="">Subject:</b> Re: [Qgis-user]
wishing for accurate lattitude/longitude
from a cell phone
<div class=""> </div>
</div>
<div class=""><span class="">
<div class="">CAUTION: This mail comes
from outside the University. Please
consider this before opening
attachments, clicking links, or
acting on the content.<br class="">
<br class="">
Hi,<br class="">
<br class="">
This is a very interesting list. It
basically confirms what I thought.
Consumer Point and shoot deceives
are all around 2-6m with no canopy.
The average multiple positions
basically give you a better idea as
a gps may get lucky. It would be
nice to have the full methodology
for this and more data (like the
number of satellite and the position
of the constellation and the gps
price list) but it’s very
interesting none the less. I was
also happy that the data confirms
the precision of the gps Sx-Blue 11.
This claims to be sub meter and my
tests indicated that on our office
unit but it’s nice to see it done
elsewhere. For about 2000$, this
gps is pretty good. As for the rest,
the difference between 150$ and
1000$ is probably more a function
of the options (like maps and screen
size...) and not a question of
precision. It would be nice to know
what gps chips they are running...<br
class="">
<br class="">
Interesting thing also is that based
on my reviewing the data on my phone
(without graph or cross tabulation
tables) is that the Glonas
Constellation does not seem to help
much. Quick stats on this list
would confirm this. Maybe this is
just a figment of my imagination
because there’s only so much
information you can grad without
running proper stats.<br class="">
<br class="">
Thanks for the post.<br class="">
<br class="">
Nicolas Cadieux<br class="">
Ça va bien aller!<br class="">
<br class="">
> Le 23 mai 2020 à 09:02, Randal
Hale <a
href="mailto:rjhale@northrivergeographic.com"
target="_blank" class=""
moz-do-not-send="true">
<rjhale@northrivergeographic.com></a> a écrit :<br class="">
><br class="">
> One other thing that may or
may not be of use but the USDA
Forest Service Publishes a GPS
Receiver Report that covers phones -
and that's helped if I've had a
client go "Well I have a Apple
<something> or a Android
<thing>". At least I feel
slightly better going "good enough"
or "no not good enough".<br class="">
><br class="">
> It should be good worldwide
(but I will admit I think phones are
my 'tech ceiling' these days) but
your mileage may vary.<br class="">
><br class="">
> <a
href="https://www.fs.fed.us/database/gps/mtdcrept/accuracy/index.htm"
target="_blank" class=""
moz-do-not-send="true">
https://www.fs.fed.us/database/gps/mtdcrept/accuracy/index.htm</a><br
class="">
><br class="">
> Randy<br class="">
><br class="">
>> On 5/22/20 8:55 PM,
Priv.-Doz. Dr. Maria Shinoto wrote:<br
class="">
>> Somehow I did not follow
the discussion, but like to add some
of our experience.<br class="">
>><br class="">
>> We are doing field work in
a remote region in the southern
Japanese mountains, archaeological
surveys on the ground based on LiDAR
data.<br class="">
>><br class="">
>> A simple Garmin etrex10 is
mostly reliable in an area of 40cm
by 40cm around a measured point, if
used repeatedly at this point and
the point is located in the middle
of a valley. Even cell phones do a
good enough job. As soon as we get
closer to the steep slopes, the
accuracy of the Garmin is less than
5 to 10 meters. We can check this
with the detailed LiDAR based map,
and geologists told us, that even an
expensive device could not be more
precise under these conditions. So
we decided to measure traditionally
on the ground if precise measure is
necessary, otherwise note the GPS
data and the location as shown in
the map.<br class="">
>><br class="">
>> To sum up, we came to the
conclusion not to spend money on an
expensive GPS that may not work in
the shadow of steep slopes -- or in
the streets of New York. -- I
appreciate any additional advice,
and hope that this experience can
save Steve's organisation some
money...<br class="">
>><br class="">
>> Best,<br class="">
>> Maria<br class="">
>><br class="">
>><br class="">
>><br class="">
>>>> Am 23.05.2020 um
03:54 schrieb Stephen Sacks <a
href="mailto:sacks44@earthlink.net"
target="_blank" class=""
moz-do-not-send="true">
<sacks44@earthlink.net></a>:<br
class="">
>>><br class="">
>>> 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.<br
class="">
>>><br class="">
>>><br class="">
>>> Message from Neil B:<br
class="">
>>><br class="">
>>> Hello Stephen.<br
class="">
>>> Glad that you're having
su<br class="">
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