Trimble VRS dual station observation

S. Clark Tompkins, if you are using single base lines you can choose whatever base you want by selecting it from the menu. If you are using multiple baselines in a true VRS solution I don't believe there is a way of selecting different bases. The system reads where you are then automatically selects the best solution off multiple base stations.

PSS

The way to choose it is buy the Broadcast format option in your survey style.
For VRS....use VRS(CMR)
For Single Base Solutions...choose CMR+, just like you would with regular RTK...you can then pick your base station.

IF....your VRS supports that option. Not all of them do.

MoDOT does not...

You could just try it and see.

I meant to say...
By choosing that option in Survey Styles>your survey style>Rover Options>Broadcast Format...

In a VRS solution, individual base station locations are typically not a concern for the user. All stations contribute to a network position solution determined at the rover.

If the user is looking for single baseline solutions between multiple RTK base stations broadcasting CMR+ to observations taken at the rover in turn then it should function as Tom suggests.

Assuming the latter, a related question might be what is the expected benefit of doing so? If a position is observed at an unknown point C using the RTK correction from a base station at control point A, then reobserved immediately using the RTK correction from another base station at control point B, what might be deduced if:

1. The two positions observed at point C agree within the tolerances of the project.

or

2. The two positions observed at point C do NOT agree within the tolerances of the project.

As Mr. Magic asks...what is the benefit of using the two different single bases? Typically they can be at some distance from the rover...and while it gives you some redundancy...

A better solution is gained by using the networked VRS solution....and observing the point more than once...Ideally seperated by some time....like 30 minutes or more...but just causing the rover to lose intialization and regain it and reshoot the point is much better than nothing.

When we were building and testing the MoDOT VRS, we did lots of shots on points using the VRS solution and checking it from multiple single bases...and most shots checked very closely.

So...done with the rambling...

Tom,
was wondering about the 30',
we wait at least 4 hrs, for different sat constellation,
mostly on another (time of the) day.
Speaking of control points here, topo points are not doubled.

or is there something else to consider,

Chr,

We do a lot of Corp of Engineer work where we are and it is a requirement to use two different bases for a single control point and either average a series of observations for the same point from two different bases (which with a traditional base and rover is simple), but with the VRS I have played with the VRS(CMR+), which is what we use, but haven't found the magical formula yet. I might be misunderstanding the way VRS works. It was my assumption that it automatically goes for the closest or most available station for a solution. If, lets say, I could change stations for a single point and average those for checks, tolerances, and overall accuracy is there a way to do that?

Another detail I just thought to add is that we are piggy backing off of the ODOT network, I assumed it was a program setting or option that we could change, never accounted for the network as maybe being a limiting factor.

> Assuming the latter, a related question might be what is the expected benefit of doing so? If a position is observed at an unknown point C using the RTK correction from a base station at control point A, then reobserved immediately using the RTK correction from another base station at control point B, what might be deduced if:
>
> 1. The two positions observed at point C agree within the tolerances of the project.
>
> or
>
> 2. The two positions observed at point C do NOT agree within the tolerances of the project.

If one observes multiple stations from two different base stations loops can be formed and the RTK vectors included in a least squares adjustment. This would not be practical for topo shots but for observed control points it provides statistical verification of the quality of the work performed.

Peter Lazio

In Belgium we work with the Trimble VRS network maintained by the Flemish Government.
Over here the RTK system is configured that way that we send our position to a central server, the system calculates a Virtual Reference Station very near to our location, this VRS is the result of at least 5 CORS placed on a grid around the country. We have up to 40 of these receivers in our small country (200x300km)
[Our survey style uses VRS(RTCM)]

So I think I can say the second measurement is always to another base = another calculated VRS
That's the way I understand it.

We do have an option not to use the VRS solution, then we get corrections from the Nearest Station [Survey Style = Multi Station (RTCM)]

Chr

Christ: It is my understanding, and I could be wrong, that the satellite constellation changes enough in 30 minutes to give you an independent check.

Four hours is better, but sometimes you do not have the 4 hours....

So if I understand correctly choosing "Multiple Station (CMR)" allows you to select a SINGLE base from a list of multiple available stations. So the name is misleading as it performs only a single base solution.?ÿ

?ÿ

This topic is 9 yrs old but still actual.

you have it figured out Sam!

?ÿ

chr.