what it says......
does it make sense?
It means what it says. You have three choices:
1) Single Observation: TBC holds one observation and everything else is just used as a comparison - for instance, in a Point Derivation Report (if you're not familiar with this report, you may want to check it out)
2) Weighted Mean of Like Observations: will compute a weighted mean, as it says, of like observations; RTK, total station, etc. RTK, for instance, is weighted by the covariance data of the observations.
3) Weighted Mean of All Observations: Will calculate a weighted mean of all observations to a point, weighting the observation by whatever you have set for Default Standard Errors in your Project Settings.
> It means what it says. You have three choices:
>
> 1) Single Observation: TBC holds one observation and everything else is just used as a comparison - for instance, in a Point Derivation Report (if you're not familiar with this report, you may want to check it out)
>
> 2) Weighted Mean of Like Observations: will compute a weighted mean, as it says, of like observations; RTK, total station, etc. RTK, for instance, is weighted by the covariance data of the observations.
>
That's NOT what it says...it says short observations have more weight than long observations
> what it says......
> does it make sense?
Trimble's
Blasted
Confusion
If it is easy, TBC makes it hard.
It makes perfect sense that shorter observations would be weighted heavier than longer observations, at least with RTK.
Not sure where you see that, this is straight from the Help:
As is this:
My snip is straight from project setting> computations
> It makes perfect sense that shorter observations would be weighted heavier than longer observations, at least with RTK.
M'kay - so if I shoot a point as an observed control point for 60 epochs- then later for 600 epochs - the pragr is correct in assigning greater weight to the 60 epoch observations....
It would appear that they contradict themselves...
I've always understood the weighting to be based on the precision of the measurement, I never even noticed that bit at the bottom of the Computations screen. Obviously, there could be circumstances where a longer shot would have better precisions than a shorter shot.
I don't have any good connections in the TBC group but I'm going to try to get an answer from Trimble on this.
"It makes perfect sense that shorter observations would be weighted heavier than longer observations, at least with RTK."
That doesn't make any sense to me at all. Please elaborate...
Do they mean shorter in time or shorter in distance?
By shorter I meant in distance, not in observation time. All else being equal, the ppm error in an RTK vector is going to make a short vector more precise than a long vector.
By no means did I mean to imply that it would be correct to weight vectors purely on their length.
They would have to mean shorter distance but that still doesn't make sense; I don't want a 3 second shot in the trees weighted heavier than a 20 second shot in the wide open at any reasonable distance.
Lee D, post: 316999, member: 7971 wrote: I've always understood the weighting to be based on the precision of the measurement, I never even noticed that bit at the bottom of the Computations screen. Obviously, there could be circumstances where a longer shot would have better precisions than a shorter shot.
I don't have any good connections in the TBC group but I'm going to try to get an answer from Trimble on this.
[USER=7971]@Lee D[/USER] -
did you ever hear from anyone at Trimble on this?
No I'm afraid not but I'll try another inquiry