Correct a "here" base position

[Symon]

Hi all,

We've recently acquired a pair of LS's to use as a base and rover (dealer sold a couple of demo units) and our current workflow is to set the base up randomly and then survey a point with known coordinates using the rover and then in the controller apply a correction/translation so that effectively the xyz "here" position the base is broadcasting is corrected to the true position. This is without having to return to the base.

Looking at the localisation functions in the LS it looks like you take the shot on the known coordinate point but then you have to go back and restart the base on the new calculated position? I'm sure there must be a way to do it similar to what we are used to as I see someone puts their base on their truck roof so must be needing to do this all the time?

Thanks

 

[Matt Johnson]

See the information about Real-Time Position Shift in the Quick Start Guide:

 

[Symon]

Thanks Matt, I presume the true coordinates are still stored in behind? Say you adjust on the first control point and then visit a couple others and the first one is wrong you could then go to the other ones and adjust on those ones instead?

 

[Matt Johnson]

Yes, you could do this. Some explanation of how coordinates are stored in the database is also given in the Quick Start Guide:

 

[Shawn Billings]

Looking at the localisation functions in the LS it looks like you take the shot on the known coordinate point but then you have to go back and restart the base on the new calculated position? I'm sure there must be a way to do it similar to what we are used to as I see someone puts their base on their truck roof so must be needing to do this all the time?

Symon,
Unfortunately the documentation regarding localizations in the manual for J-Field is out of date. For your purposes, Matt's recommendation to use Shift is the right course. The other application you may also consider is M-Local. It works very similarly to Shift except that it allows for more than one control point to be used. Both Shift and M-Local are only 3-parameter transformations (translate N, E and U or if you prefer, X, Y and Z).

Localization is best used for developing a plane coordinate system from one or more points. The developed coordinate system has 7-parameters (translate N, E, U, rotation about the N-axis, the E-axis and the U-axis, and scale).

The best documentation available for localizations (that I am aware of) are these two videos:

 

[Matt Johnson]

Unfortunately the documentation regarding localizations in the manual for J-Field is out of date.

I updated the information about localizations and removed the documentation about using localizations to adjust the base position from the 2016 version of the manual.

M-Local is also covered in the Quick Start Guide:

 

[Symon]

Here in NZ use use local grid systems for cadastral (and most other surveying) that are based on GRS1980; as far as I can tell they are similar to your low distortion projections where the mean sea level/ellipsoidal distances and the grid distance are close enough to each other over urban sites to be considered the same for practical purposes. Our cadastral survey datasets (plans) show grid azimuths and ellipsoidal distances which are recorded in Landonline a government database. I've attached an example if anyone is interested

All we typically want to do is set the base up with a "here" position and visit a single control point with a correct grid coordinate and then adjust the base coordinate as if we started it running on true coordinates (no rotating or scaling for us; too hard to unravel the mess later if you apply it wrong). Then we can locate our other pre-calculated coordinates on the local grid.

Looks like the m-local is the ticket for what we are after as it means we can average the shift from control points if necessary (and the real time shift would be ok too for 90% of jobs), thanks Matt and Shawn for your assistance!

 

[Shawn Billings]

You may find this video helpful regarding Shift:

 

[Symon]

Thanks Shawn will add it to the essential viewing