F9P Surveying In

Just wondering, with regard to surveying in, If I were to state a time but then a possibly unattainable accuracy level, will I be able to see and record the mean position if I stop the process manually before it (never) finishes. I could obviously enter these positions manually afterwards.

Secondly, I assume there is no merit in increasing the gps frequency for surveying in, to get more samples quickly? My assumption would be that the satellite drift we are monitoring is a slow changing parameter anyway.

Hi Alan, when I did mine I had a similar conundrum and settled on the other way round. i.e set a long time that I decided I could live with (or more to the point, what my impatience would allow! ). During this time I used the relevant tab in messages to view the current survey position ‘live’, as it were. Got down to 72mm in about 12 hours. Once it got to about 75mm it was very slow to improve. I tried your suggestion as well and took a photo of the lat and long before cutting it short, then entered those coordinates, but the accuracy widened for some reason and so I started again and left it to finish the next time, as above. Might do it for longer sometime, but happy for now.

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Which figure did you photograph? I’m not sure which is the averaged figure. The one in the data window is moving too much to be the average IMHO. Do you mean the Mean ECEF figures in SVIN or something from PVT?

Mine has been running for 30 hours now and has got down to 53.8mm. I set 50mm as a goal so it might actually reach it.

[Edit…]

31.5 hours and now down to 52.3mm

I’m now wondering just how low it would go if I left it running indefinately with a very low goal? :thinking:

Have you considered post-processing services to determine the base location accurately?

You have to make a log of specific data for something like 24 hours at 30 second sampling rate. Then convert the product specific log into a rinex file and submit that file to some on-line service.

I’d done it with one Canadian site:

as well as an Australian site:

Read instructions carefully, submit your data and they should provide you your base location at better than 0.5 cm accuracy.

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Ok thanks. This sounds excellent. I will check out you links and see if I understand it!

It got to 50mm in just under 34 hours 24 minutes.

I’ve bookmarked both sites and am attempting to understand them!

Yes it was the mean ECEF figures in SVIN Alan. 50mm sounds pretty good though?

I’m curious Alan did you ever end up trying the trig point method or figure out how accurate the trig points in your area are supposed to be?

Hello and welcome NorthernFarmer.
Can you explain how to create a data log and convert it to a Rinex file.
(I think many of us are new to the advanced use of antennas)
Thank you in advance!

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Sorry clod.fr but I have not done the survey with a u-blox F9P.

A manufacturer specific raw log file is typically needed first. The file is then converted to RINEX format. I have done it with my Novatel dual constellation receiver with the following raw log commands:
RANGEB ontime 30
BESTPOSB once
IONUTCB onchanged
RAWEPHEMB onchanged
GLORAWEPHEMB onchanged
VERSIONB once

Novatel provides a tool that converts the binary log file to rinex format. This converted file can then be uploaded directly for on-line analysis.

At a quick glance I did not find instructions from u-blox to perform the raw log but google points to some success cases. Here an example that might show one way forward:
https://portal.u-blox.com/s/question/0D52p00008WTLQyCAP/how-to-save-data-from-a-logfileubx-to-a-rinex-format-

I’m sure the u-blox support site would be able to help if you ask there.

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This is what i did few weeks ago.
I have a f9p with ardusimple xbee wifi ntrip master.
First of all update firware of f9p, then i use the config file for base from ardusimple. I connect the f9p to a windows computer and connect it to u center. In the msg view you have to disable all the msg (right click on the black and disable) and enable rmx-rawx and rmx-sfrbx. Then disconnect u center and open strsvr from rtklib and you could configure what you need to store.

Hope this help

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I did that for post processing to know the position of my base station and to compare i did the survey in (10h) and there was a meter between the two position and in geoportail (google earth for france!) the post processing position match exactly with the satelite photo.

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Well, not very accurate at all from what I can find out . I have been struggling a bit with my caster choice’s too so checking hasn’t even been possible yet.

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Managed to get my esp32 to talk to rtk2go so later in the week I might try the local trig points, out of interest.

Failing miserably to run my own caster! Neither snip, RpiNtripBase or WifiNtripMaster want to talk to the outside world, despite snip managing to produce an outwardly visible caster table.

these are the the steps i followed hopefully it saves the next guy some time.
i’m using the simpleRTK2B

Quote from Natural Resources Canada

  • FINAL (+/- 2 cm): combined weekly and available 13 -15 days after the end of the week
  • RAPID (+/- 5 cm): available the next day
  • ULTRA RAPID (+/- 15 cm): available every 90 minutes (not available to download)

It is preferable to compute the base station’s coordinates before starting the Real Time Kinematic (RTK) work. You could setup the base station ahead of time and collect raw GNSS data (anywhere from 2hrs to 24 hrs depending on the accuracy required). Leave the base station in place. Transform the raw data to RINEX and submit it for Static CSRS-PPP processing. CSRS-PPP can process the data approximately 90 minutes after data collection.

what you need to do.

  1. Survey in your base station using u-center. i surveyed for 12 hours until my accuracy was not getting any better.
  2. switch timemode3 to fix mode from survey in. enter static coordinates you just surveyed in.
  3. right click on UBX->RXM->RAWX and enable messages.
  4. change your usb port to only output UBX. UBX->CFG->PRT change taget to the port youare using. you only need to set the output to UBX
  5. Disconnect u-center from the ZED-F9P
  6. downloaded RTKLIB from this site. it was suppose to have support for the newer ZED-F9P.
  7. un-zip rtk Lib
  8. run strsvr. input will be the serial pot you are connected to. use the same connection setting u-center was using. set the output to a text file.(you are taking a serial strean that is UBX and saving it to a text file. you defined UBX in ucenter)
    image
  9. collect data as long as you want to. 1 week = 2cm, 1 day = 5cm 90min = 15cm. longer the better. Government of Canada website has a max upload of 300mbyte. i collected data for the first 24 hours. submitted my result. then i ran it again for 1 week.
  10. open rtkconv.exe select the file you just created. change format to u-blox. set the location to save the output files.
    image
  11. click convert. this should create a .obs file(this is what you can upload to the Canadian government site.)
  12. go to Precise Point Positioning
    create an account if needed.
  13. select a epoch data to use and select the .obs file you created to upload. if there are multiple files. you can zip them together. zipping will also create a smaller file to upload.
    14.click “summit to PPP”
  14. wait about 90 min to receive an email with the results. my new coordinates were in “out_pitfile_test.sum”
  15. enter the new coordinates in timemode3 in ucenter UBX->CFG->TMMODE3

i’m just running this now. i ran a small test that did not improve my accuracy because it was only 5 min. ill update this afternoon with my results. current accuracy is .5 meters. Also my antenna is not on a metel plate yet.

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A quick and dirty way without resorting to offline post processing is to use ucenter to provide an NTRIP feed from the nearest base station and run the f9p in RTK mode. You should get within a centimeter or two quite quickly, but accuracy depends on the accuracy of that base station position plus/minus 10 mm plus/minus 1mm/km baseline. Post processing won’t necessarily get any more accurate unless it’s via a more accurate or nearer reference station.

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i set up NTRIP and was able to survey my antenna to .08 meters. this worked OK. but after i submitted 24 hours of RINEX observation data to natural resources canada. i was able to get .013 meters of accuracy. the quick and dirty way worked but it was defiantly worth the time to record 24 hours of data and submit it.

image

Has anyone submitted data from a Swift Piksi Multi base to Natural Resources Canada? I’m trying to figure out what data to output to the file.

google swift binary protocol to Rinex. see this link.

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I also took some time to get the precise position of my base station. I think I can complete your guide.

What you suggest here is to perform a PPP (Precise Point Positionning) calculation to post process the observation. In short, you have a raw file in RINEX format, and the NRCAN compensates each position according to the data they have about orbit errors, atmospheric perturbation, etc. That’s why you have to wait before using the service, and the more you wait, the more their correction data is precise. It should work well. Take note that the position of your base station will be expressed in the system coordinates you chose (ITRF or NAD83). It may not be the system used in your country ! (for example in France, the official system is RFGF93).

There is at least one other post processing method you can use, which is differential GNSS. It’s quite like the RTK solution suggested by arwoodridge, but it’s not in real time. Basically, you chose a local base station (they are called CORS station in the USA for example). In general, they are operated by the state, and you can trust their position down to a few millimeters. You should be able to get their RINEX observation one way or another. Choose a file according to your own observation window. Then, use RTKPOST with both observation files in static mode to get your base station position. Its coordinates will be expressed in the same system as the position of your local reference station (probably the official system for your country).

A good idea is to compare results from both methods to make sure you have a reliable position.

I discussed more about it for the specific case of France here : Service PPP gratuit en France (in french of course)

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