Should base continue to use corrections from NTRIP after FIX?

Hi, I am currently testing two emlid systems. M2’s with LoRa Radio connection. I have one set up as a base, the other setup as a rover. The base is using an NTRIP service to establish static coordinates to get FIX, which I then average over 30 minutes. Once that is established, I connect the rover to the base via LoRA. The rover seems to be receiving corrections just fine (in fact, it is receiving MORE corrections for satellites because the NTRIP only sends for GPS and GLONASS). My question is, does it matter if i turn off the NTRIP service to the base at this point? I’m assuming the LoRa corrections are being broadcast relative to the fixed base coordinates from the 30 minutes average and the NTRIP service is no longer relevant. Any clarity would be helpful. Thank you in advance.

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I am pretty sure that once your second base has its coordinates locked in all corrections are based off those coordinates and what it is measuring at the second base antenna.

It would improve absolute accuracy of a point measured from the second base since it was obtaining a fix from the first base with a known point. Once the second base point is known and locked in, i do not see a reason for the second base to stay connected to corrections.

If you change base coordinates at the same base location it will offset all of your previous measurements each time.

But this is a very good question, I also look forward to emlids @liudmila.slepova @tatiana.andreeva @artem.fomenko answer to this.

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That’s my workflow as well, and it works great. Only difference is I have 2 RS+ units, one as base that I establish cm-accurate location using NTRIP. Once the base position is established from an average of fix solutions using NTRIP corrections, you have a real-world accuracy of +/- 1 cm for the base location and there’s no need to continue receiving NTRIP corrections, assuming that you don’t move the base.

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Thank you, that gives me more confidence with the system. If I may ask one more question. Once I establish my base and connect my rover I wait to get a FIX on the rover and then take a measurement (usually a 2 minute average) and then walk somewhere and take another measurement. I noticed that the FIX status would remain even while I was walking around. I was under the impression that once I move my rover to the next measurement, I would ‘break’ FIX (float) and then have to re-establish FIX once I settled over my next location. FIX seemed to stay the whole time. So, my question is, once you have fix, am I free to roam around and take immediate measurements? Should I reset the FIX somehow for each measurement? I apologize if my question is not well worded as I am still learning. Thank you.

I suggest reading this Emlid doc for more information about NTRIP and the base setup: https://docs.emlid.com/reachrs2/common/tutorials/placing-the-base/

And look at the bottom of this doc for a brief explanation of the difference between single, float, and fix solutions for the rover: https://docs.emlid.com/reachrs2/common/reachview/status/

Short answer is that it’s normal for fix to hold while you move. No need to reset for each point, that’s the beauty of fix-and-hold RTK, you can shoot points quickly. So yes, you’re free to roam around and take points immediately while retaining “fix” status. The system is not fool-proof however, so be sure to educate yourself a bit more about how it works and about some basic surveying best-practices so that you can double-check that you’re getting good data.

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It depends on the collection mode, is the short answer.

If you are collecting static points in Static mode (set in RTK settings of ReachView) moving from one point to another will momentarily break the fix on multifrq systems. On the single-frq systems I would not recommend mode for obs times under 30 mins, as the initialization time is much longer than the multifrq systems.

If you are collecting points in Kinematic mode, you will not see your fix break, unless your outside environment changes enough so not enough sats are visible.

When you walk around, and if you indeed to post process your data, always select routes that will maintain a good sky view. Maintaining the fix will give you a more robust solution. This is especially the case with Single frq system!

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Hi @jherbranson,

Agree with Evan and Christian regarding connecting the base to NTRIP and the retaining Fix.

I want to notice that you need to click on the Save coordinates icon when the position is averaged. In this case, Reach will transmit it in corrections until the next averaging - even if you disconnect Reach from NTRIP or turn it off for a while.

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