Ntrip varying a lot

In an ntrip survey with a baseline of 11,800m we noticed an oscillation in the collection of points.
We collected some points and then, when making a conference making the stake, the position varied on average 10cm.
I thought it was very careful in view of the baseline and the equipment used.
I use the ntrip base with the M2 and the rover an RS2.

Does anyone have any settings tips or how can I fix this?

As I use ntrip for urban survey this accuracy is too bad.

We did the test as follows:

  1. We collect the fixed point;
  2. We force the RS to float, covering the receiver with our hand;
  3. Hope to fix again;
  4. We collect the fixed point again;

Did you perform the same test connecting to one of the IBGE bases? They are, by Brazilian law, a first-order network, that is, they define the accuracy parameter for all points or landmarks in Brazil.

Another test, to find out if your M2 base has a good coordinate solution, is to stakeout one of the RBMC landmarks spread across the Brazilian territory.

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7mm+1mm/km dilution is the stated change in accuracy as the baseline gets further.

11.8km*1mm + 7mm = 18.8mm

Since the error could end up + or - would not be surprised 40mm of error between points under perfect conditions.

Using ntrip to set up a local base will shrink your baseline to get more accurate local measurements.

And then there is all the post processing techniques the surveyors use.


How did you set the M2 base? Do you have the M2 working 24/7?
The test you did (collection of points and stake out) occurred the same day?
You must give more info to troubleshoot the problem.
Maybe the RS2 was float during the stake out and you didn’t noticed that?

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I configured the M2 as per Emlid’s specifications.
My base is 24/7 yes.

We always took care to ensure collection with a fixed solution, I’m sure it wasn’t floating.

Hi Mauricio,

Do you have the logs I could take a look at? Want to have the complete picture. If you don’t feel comfortable sharing them in public, you can send them to support@emlid.com.

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Are you using the helical antenna? They are great for drones and tractors because they keep signal and fix in some really challenging, dirty, covered, terrible conditions, but at the cost of a bit of accuracy.

If your looking for more accuracy try the larger survey antennas

This one is cheap and works well for me, but I still think the one in the rs2 is more accurate. But the 7mm+1mm/km still applies to all of them. So the antenna type may only make 0-60mm of difference in your measurement.

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So the M2 base shouldn’t be the problem.
One other thing that may affect the solution is the correction age. Maybe the cell signal was not so good at that time? Did you made another stake out test another day?
Since M2 works 24/7 you could do some more testing with the collected points.

Do you think this antenna is good?
This one does not support L5 and the extra frequencies of the other systems.
I think Beitian puts D or S to distinguish the antennas eg BT-300D or BT-300S.

I use this antenna:

I believe that neither the antenna nor the M2 is a problem.

What firmware version are you using?

did that just happen one day your collection Ang checking?

The link is wrong. Put the correct one if you want.

Go for a Harxon/Swiftnav GPS500. NGS calibrated for around 200 USD (or less).


This might be interesting




We ran a new test today, forcing it to float.
Today, the result was as expected.
The position was always maintained when fixing.

Could it be related to the time of the survey?
I know that here, in my region, the time between 1pm and 3pm +/- has a significant reduction in satellite coverage.

I don’t see another explanation.

But the other survey was carried out after 17hrs.