RTK2B Altitude Accuracy

Does anyone have an tips for improving altitude accuracy on the simpleRTK2b boards?

I am trying to develop a function that maps fields and contours with a high degree of accuracy and am getting good GPS results, but less good altitude ones. According to the ardusimple site, the RTK2B board is capable of producing results to within a 2.5CM degree of accuracy, but after leaving mine running in a fixed position for over 10 hours it is fluctuating by anything up to 1M over a period of a minute.

Is the claimed 2.5CM really achievable? Or anything remotely close?

I use a Sparkfun F9P to do some surveying and it seemed stable to a little more than a inch. Definitely more stable than 1 metre. I did some redumentary drainage planning it last spring and the tile plow contractor confirmed our findings with his Trimble unit.

Dual receivers depends on a stable elevation to calculate the roll, and that seems to work for folks. Not sure why you’re having this issue.

The simpleRTK2b does sub 2.5 cm vertical accuracy with RTK.
From my experience I would say ±8mm with a base 5 km away

But in simple mode not! even if you survey many days!
You Have to postprocess or connect to an other base to have the absolute coordinate for your base.

Higher rate of messages from base, set base to 5 or 10hz.

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Is that a personal opinion or do you have some documents or studies for reference?

There is no good study that looked at this specifically.

higher base rate is just burden on radios or data for most applications only for higher speed topography, moving base and other specialised applications it is proven useful.

For mapping fields it is probably most efficient to record while doing some other job on filed. For that speed 1hz base would be sufficient.

If you want to record elevation with antenna on car roof with high speed then higher base output should be useful.

What was your horizontal accuracy did you get 2.5cm horizontal 1m vertical accuracy ? With RTK even if your base absolute elevation is wrong rover relative to base should stay in 2.5cm accuracy.

I don’t think any of the interviewed companies promoted higher RTK correction signal rates. For a fast moving rover everyone promotes high navigation rates but that can well be done with the typical 1 Hz RTK base.

The RTK correction signal is not changing too rapidly. Extrapolation for higher navigation rate gives very accurately the same correction signal as if the base was running faster than at 1 Hz.

Extrapolation does not work for navigation output “equally far to the future”.

For most applications 1hz is good. If tractor is used to record than more then enough.

This can be one of special application where higher rate can be useful if instead of tractor SUV / ATV or car is used to faster map fields, (better to map while doing something useful in field let’s say you forgot to record, you now need data for your next job).

Maybe someone can test it (careful if you use rtk2go it only allows 1hz for base), at what speed is there noticeable difference if any.