How often is PPP'ing a base required?

I have a PPP’ed base coordinates, do the receivers account for the shifting of the plates and drift in measurement?

Will my year over year repeatable accuracy slowly be drifting my tractor into the fence line?

The locked in coordinates you think would be changing slowly, how often would the monument coordinates require maintenance?

I would like my sprayer tracks to become the next Nazca lines.

Hopefully your base and tractor are on the same plate so the drift cancels.

It won’t be an issue for your repeatability and if someone else comes along later and for some reason wants to match what you did they just need to know the base station info you used in particular the epoch (time).

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So when I enter base coordinates into the RS2, I am never asked for a time as well. Still somewhat confused, I know we are talking really tiny changes over large times.

If in ten years I had to replace the base receiver, entered the same PPP coordinates in WGS84 from 2021. How would the new RS11 know that is when they were made?

So the receiver corrects for the drift over time to keep it in relation to the plate?

The receiver doesn’t explicitly correct for drift over time, but for all practical purposes it cancels.

Maybe consider the not uncommon scenario of when you don’t have known base coordinates and you use an autonomous averaged position. This position could easily be in error of a few meters of the “true” WGS84 position, but as long as you use the same coordinates for the base you can return to the same spot(s) you previously marked. Even ten years later.

This is also why you can enter, say NAD83 coordinates for the base station and get NAD83 coordinates from the rover even though, technically, the base may expect perfect WGS84 coordinates.

These offsets from perfection cancel for differential correction as long as they aren’t huge and/or the baselines aren’t basically continental distances.

Maybe another way to put it is if you are using a WGS84(epoch 2021.0) coordinate system today you could still use that system in 2031.


Ja, I concur with @jbonde002.
Unless your fields stretched of to a different continent or state, your relative measurements with the base is what is you need to maintain. All other absolute time or location is adjusted for with the base when it is need for.
Just save your coordinates, datum and time you established the base. The End


Think I am starting to grasp this.

If my base is ppp to the local datum Nad83, all points ride the same tectonic plate the same amount overall. So relative to each other they do not change, and overall the effect of the drift is cancelled. Time almost does not matter. Everything is synced up relative to permanent ground monuments on the plates. Everything rides together. Redoing the PPP for most purposes would not matter.

If my base is PPP to WGS84, all of the relative measurements do not matter much in the same regard. But in reality my coordinates are drifting, relative to the center of the earth, fixed prime meridian, and fixed north pole . As long as I do not change base coordinates all measurements stay relative to the base coordinates and drift is still cancelled.

But redoing the WGS84 PPP at a later time I would have a different measurement showing the movement plate I am on. So time of the measurement matters in absolute terms.

I have had military training all week. I wish I would have seen this post sooner. I so wanted to reply, “I never PP on my base”

Glad you got your answer!

:joy: That is very funny.

Though learning this does not make my rows any straighter, I now grasp the concepts of WGS84 and NAD83 and why they exist at the same time.

One is used to measure the whole world and its changes over time, the other is used to measure who owns a small piece of the world for all time.

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