[Qgis-user] wishing for accurate lattitude/longitude from a cell phone
Nicolas Cadieux
nicolas.cadieux at archeotec.ca
Sat May 23 17:27:40 PDT 2020
Hi,
I see lot's of people are interested in this topic. I recommend reading
this basic Guide on GPS Positioning.
https://www.rncan.gc.ca/sites/www.nrcan.gc.ca/files/earthsciences/pdf/GPS_Guide_e/GPS_Guide_e.pdf
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.
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.
Nicolas
On 2020-05-23 4:43 p.m., Madry, Scott wrote:
> Hello all. Regarding GNSS precision, I also find useful the Trimble
> online GNSS planning website:
>
> https://www.gnssplanning.com/#/settings
>
> 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.
>
> 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.
>
> Scott Madry
>
>> On May 23, 2020, at 3:53 PM, Mike Hyslop <mdhyslop at mtu.edu
>> <mailto:mdhyslop at mtu.edu>> wrote:
>>
>> 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.
>>
>> Best,
>> Mike
>>
>> On Sat, May 23, 2020 at 3:45 PM <j.huber at post-ist-da.de
>> <mailto:j.huber at post-ist-da.de>> wrote:
>>
>> Hi Nicolas,
>>
>> 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).
>> 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...
>>
>> I agree that for precision, "old school" technology is often
>> better and cheaper, although it requires more effort than simply
>> pushing a button.
>>
>> Regards
>> Jochen
>>
>> Am 23.05.20 um 20:21 schrieb Nicolas Cadieux:
>>> Hi,
>>>
>>> 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 (https://emlid.com/reachrs/
>>> <https://emlid.com/reachrs/>) 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.
>>>
>>> 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.
>>>
>>> Have fun!
>>>
>>> Nicolas Cadieux
>>> Ça va bien aller!
>>>
>>>> Le 23 mai 2020 à 13:52, Bernd Vogelgesang
>>>> <bernd.vogelgesang at gmx.de> <mailto:bernd.vogelgesang at gmx.de> a
>>>> écrit :
>>>>
>>>>
>>>>
>>>> Unfortunately, the Forest Service Website went offline (maybe
>>>> this thread caused so much traffic that it broke down? ;) )
>>>>
>>>> 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.
>>>> 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.
>>>>
>>>> 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.
>>>> 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.
>>>> 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.
>>>>
>>>> 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.
>>>>
>>>> Furthermore, I stumble upon an article about a module with
>>>> u-blox chip. https://www.sparkfun.com/products/16481
>>>> 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.
>>>>
>>>> Cheers,
>>>>
>>>> Bernd
>>>>
>>>> On 23.05.20 18:17, Michael.Dodd wrote:
>>>>> https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/j.2041-210X.2011.00118.x
>>>>> 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.
>>>>> <https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/j.2041-210X.2011.00118.x>
>>>>>
>>>>> Where are my quadrats? Positional accuracy in fieldwork - Dodd
>>>>> - 2011 - Methods in Ecology and Evolution - Wiley Online
>>>>> Library
>>>>> <https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/j.2041-210X.2011.00118.x>
>>>>> 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.
>>>>> besjournals.onlinelibrary.wiley.com
>>>>> <http://besjournals.onlinelibrary.wiley.com/>
>>>>>
>>>>>
>>>>> ------------------------------------------------------------------------
>>>>> *From:* Qgis-user <qgis-user-bounces at lists.osgeo.org>
>>>>> <mailto:qgis-user-bounces at lists.osgeo.org> on behalf of
>>>>> Nicolas Cadieux <nicolas.cadieux at archeotec.ca>
>>>>> <mailto:nicolas.cadieux at archeotec.ca>
>>>>> *Sent:* 23 May 2020 16:34
>>>>> *To:* Randal Hale <rjhale at northrivergeographic.com>
>>>>> <mailto:rjhale at northrivergeographic.com>
>>>>> *Cc:* 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
>>>>> CAUTION: This mail comes from outside the University. Please
>>>>> consider this before opening attachments, clicking links, or
>>>>> acting on the content.
>>>>>
>>>>> Hi,
>>>>>
>>>>> 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...
>>>>>
>>>>> 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.
>>>>>
>>>>> Thanks for the post.
>>>>>
>>>>> Nicolas Cadieux
>>>>> Ça va bien aller!
>>>>>
>>>>> > Le 23 mai 2020 à 09:02, Randal Hale
>>>>> <rjhale at northrivergeographic.com>
>>>>> <mailto:rjhale at northrivergeographic.com> a écrit :
>>>>> >
>>>>> > 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".
>>>>> >
>>>>> > It should be good worldwide (but I will admit I think phones
>>>>> are my 'tech ceiling' these days) but your mileage may vary.
>>>>> >
>>>>> > https://www.fs.fed.us/database/gps/mtdcrept/accuracy/index.htm
>>>>> >
>>>>> > Randy
>>>>> >
>>>>> >> On 5/22/20 8:55 PM, Priv.-Doz. Dr. Maria Shinoto wrote:
>>>>> >> Somehow I did not follow the discussion, but like to add
>>>>> some of our experience.
>>>>> >>
>>>>> >> We are doing field work in a remote region in the southern
>>>>> Japanese mountains, archaeological surveys on the ground based
>>>>> on LiDAR data.
>>>>> >>
>>>>> >> 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.
>>>>> >>
>>>>> >> 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...
>>>>> >>
>>>>> >> Best,
>>>>> >> Maria
>>>>> >>
>>>>> >>
>>>>> >>
>>>>> >>>> Am 23.05.2020 um 03:54 schrieb Stephen Sacks
>>>>> <sacks44 at earthlink.net> <mailto:sacks44 at earthlink.net>:
>>>>> >>>
>>>>> >>> 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 su
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