Hi Scott, Nicolas, that was helpful, as well as Nicolas' advice. Thanks to you both! Maria
> Am 24.05.2020 um 10:09 schrieb Madry, Scott <[email protected]>: > > I hate to plug my own… but my book on GNSS may also be of interest, not too > much either! > > https://www.springer.com/gp/book/9781493926077 > > Scott > > > >> On May 23, 2020, at 8:27 PM, Nicolas Cadieux <[email protected]> >> wrote: >> >> 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 <[email protected]> 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 <[email protected]> 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/ ) 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 <[email protected]> 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. >>>>>>> >>>>>>> Where are my quadrats? Positional accuracy in fieldwork - Dodd - 2011 - >>>>>>> Methods in Ecology and Evolution - Wiley Online Library >>>>>>> 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 >>>>>>> >>>>>>> From: Qgis-user <[email protected]> on behalf of >>>>>>> Nicolas Cadieux <[email protected]> >>>>>>> Sent: 23 May 2020 16:34 >>>>>>> To: Randal Hale <[email protected]> >>>>>>> Cc: [email protected] <[email protected]> >>>>>>> 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 <[email protected]> >>>>>>> > 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 >>>>>>> >>>> <[email protected]>: >>>>>>> >>> >>>>>>> >>> 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 >>>>>>> _______________________________________________ >>>>>>> Qgis-user mailing list >>>>>>> [email protected] >>>>>>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user >>>>>>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user >>>>>>> >>>>>>> >>>>>>> _______________________________________________ >>>>>>> Qgis-user mailing list >>>>>>> >>>>>>> [email protected] >>>>>>> >>>>>>> List info: >>>>>>> https://lists.osgeo.org/mailman/listinfo/qgis-user >>>>>>> >>>>>>> Unsubscribe: >>>>>>> https://lists.osgeo.org/mailman/listinfo/qgis-user >>>>>> _______________________________________________ >>>>>> Qgis-user mailing list >>>>>> [email protected] >>>>>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user >>>>>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user >>>>> >>>>> >>>>> _______________________________________________ >>>>> Qgis-user mailing list >>>>> >>>>> [email protected] >>>>> >>>>> List info: >>>>> https://lists.osgeo.org/mailman/listinfo/qgis-user >>>>> >>>>> Unsubscribe: >>>>> https://lists.osgeo.org/mailman/listinfo/qgis-user >>>> >>>> >>>> _______________________________________________ >>>> Qgis-user mailing list >>>> [email protected] >>>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user >>>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user >>>> _______________________________________________ >>>> Qgis-user mailing list >>>> [email protected] >>>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user >>>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user >>> >>> >>> >>> _______________________________________________ >>> Qgis-user mailing list >>> >>> [email protected] >>> >>> List info: >>> https://lists.osgeo.org/mailman/listinfo/qgis-user >>> >>> Unsubscribe: >>> https://lists.osgeo.org/mailman/listinfo/qgis-user > > _______________________________________________ > Qgis-user mailing list > [email protected] > List info: https://lists.osgeo.org/mailman/listinfo/qgis-user > Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user _______________________________________________ Qgis-user mailing list [email protected] List info: https://lists.osgeo.org/mailman/listinfo/qgis-user Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
