Height Error when surveying

”There seems to be an error, I guess. It is always good to check your results twice before handing it to the client. Very not amusing situation.”

This is why I am hesitant to purchase an Emlid. The whole point of buying an Emlid is so that I don’t have to have a Trimble unit to check against. Does this bother anyone else? Or am I just thinking about it wrongly?

Blind trust in something is inherently bad. You should always check your results!

3 meters is way beyond stuff that has to do with what brand you are using. This is mechanical or in the setup, which could happen on any system.


The only way to doublecheck with a single system is to setup a network and occupy each point in the network while checking the others. Hoping to be right all the time without double-checks and one piece of hardware is asking for a swift kick. Besides that, Surveyor A vs Surveyor B is always a debate…

To the OP. We are about to the point that if you can’t supply details on processing or system reports then there is not much that can be analyzed and further without having it in our hands.


As the error in Z is a constant of 3.084 m (sd 0.015), it is only an offset forgotten somewhere, or a bad translation between 2 datums. As long as the relative z difference between GCP are ok, your Reachs are working well.


I was not bothered until this happened.

Hello, can you please tell me more?. Because I don´t see anything about a offset in the reachview app, and there I have checked the ellisoid to geoid conversion.

Sorry, I don´t understand very well. I did the survey with reachview and the converted using a official app (programa de aplicaciones geodesicas) , but I also check again the conversion.

We need to think about the whole workflow and all the places that a base and rover (drone) antenna height need to be accounted for. First you have you base setup and because it was connected to a service, what was the sate of that service. The stemming from that you set GCPs from that derived base point. Then you flew and brought your GCPs into some (we don’t know what) PPK software to resolve the corrections and put the drone images into another piece of software (we don’t know what) for photogrammetry. Then the GCPs that had an error of approximately 3m were entered into the PG software and resolved with the 2m initial 2m error in image positions. We also don’t know what the error in accuracy was on the final surface from the PG processing. The only real clues you have provided is related to the control that the data was derived from and not what happened to it after that. That all said I find it hard to really analyze what happened any further.

In base mode Reachview on the Base, what did you enter as antenna-height?

When you did the survey in Reachview, what did you input as the rover antenna height?

When you submitted the rinex file for processing, did you input the antenna heights for both rover and base rinex file when converting from ubx?


I have seen people messing with Leica equipment. If you buy an Emlid product you do that because the additional time you need with this equipment costs less money than a Leica or Trimble. You can mess with a Trimbel but there are more chances to mess with a Reach device.

If you use the equipment every day and you are short in time than it is better to go with a expensive but less complicated solution (and wait for the RS3+).

If you have some time and some understanding what you are doing than you can achieve very good accuracy even with the original Reach RTK. I still think they are more than good enough for what I do (I want to have an accuracy below 5cm (after conversion into ETRS89/UTM and DHHN2016) and you can achieve that.).

But if I would do jobs every day I would go for a Leica and only use Emlid on board of my drones.

The antena height in the base was set with a fix rtk solution with a ntrip corrección provider.
Rover antena height was set as the lenght if the pole with the thread adapter, I has checked this.
I dont use ppk when sureveying.


I guess you got the base position by averaging fix. So the position you got is the position of the antenna.

Then you need to assess what the pole length did with your coordinates.

If you added the length later or the averageing does consider the pole length (I do not know, I only do PPK) and you did not add it you get an error.

Did you ask your client to measure the position of youre base? I think that schould give a good indication where the error happend.

Did you collect the raw-log as well, on both base and rover?

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