Trimble Access Resection Routine

@stephen-ward

1:

Unfortunately there is no way to recompute a resection in Access, but you can in TBC.

The resected point is held as XYZ - you can change the height of the point using station elevation, or by just editing the point.

If your observations are stored as AzHzSd the heights, and assuming your HI and HT are correct, will flow through automatically.

2:

Some datasets are 2D only - for example NZ cadastral surveys - or maybe you have mixed data. Sometimes it is just easier not to have to worry about Z at all.

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You need this when your control is 2d - sometimes from a dxf in our case.

Perform a station elevation after the resection. This can be 1 or more points with an elevation keyed in only, no need voor E,N.
We used it before to get elevations that way. When you know the level of a manhole cover you can start from that. Shoot it and from that moment all your points from that station will have elevations.

I always found this a neat routine in Trimble Acces!

Resection routine in Access has now just lost the 'end face' and 'add point' menu options at the bottom of the screen.   

Haven't seen this problem before.  I had used another S5 while ours was sent in for calibration.

Took three or four tries to get the menu options to appear, and the resection worked.

Got our S5 back, and the same three or four tries to resect still happened.

Now the same three or four tries won't cut it.  It's left me guessing here.

@rj-schneider 

Just did a quick test and it seems to be working for me in v2022.11:

Report this stuff to your dealer, they can get it to Trimble and get someone working on it.

@rover83   I found it will work, if, it is not the first routine you run after set-up.

The part I didn't understand was I had done the very same thing numerous times without fail.

And this might be of some help to someone, somewhere; After you have set the instrument up,

run a set of angles to something, this populates the bottom menu with the 'end face' and 'add point' buttons that seem to be missing.      I have no idea why.

edit: The buttons will be there if you run a resection.

I'll probably get blowback from this but it's my opinion that resections are a risky thing and in cases where the DC software isn't cooperating, you are burning sunlight instead of just taking the time to set a point from two known points and checking in to another.  Because you can doesn't always mean that you should resect.

Nobody should ever use a routine on their DC if they can't calculate it by hand to check the solution or to calculate one if there is a software issue.

I'll probably get blowback from this

Not here.  You're either out in the field doing that, or sitting around posting about it.

I can cover those requirements.

I'll probably get blowback from this but it's my opinion that resections are a risky thing and in cases where the DC software isn't cooperating, you are burning sunlight instead of just taking the time to set a point from two known points and checking in to another.  Because you can doesn't always mean that you should resect.

Nobody should ever use a routine on their DC if they can't calculate it by hand to check the solution or to calculate one if there is a software issue.

Eh, we're not talking about calculations, but about software functions mysteriously (?) going away. (I can't hand-compute an RTK vector solution, so maybe I shouldn't do RTK work.)

Like any other tool, when properly applied and with proper understanding, resections are fine.

Trimble even provides white papers to explain what's going on under the hood for the two types of resection options. The math is pretty simple and the procedures explained well.

@chris-bouffard Trimble actually uses two different mathematical equations depending on how many known points used and such.  They have a awesomeness white paper that has all the formulas and such. I have always loved resections for a lot of reasons but one being it can be a lot better than slinging a fly in the right circumstances for sure. The old days of doing everything long hand got a lot of people scared of them and they never allowed them and some still do not. Once you read the white paper on how trimble Access does it and have the knowledge of the uncertainty of the control in which you are resecting from then all those myths about never resect in a straight line or its not accurate etc just disappear.   I had to do a proof once. Had a surveyor put a point any distance he wanted off a line between two other points he had set. As long as he set them all tight and i would be able to tell him how close i was to true line and see how he thought it worked. He now does resections.  He set the point.05 ft off the line and i had to resect from not equal distances. If the control is good and set up centering error good no issues.

@rover83 

I did resections before having any programs that did it. It's trivial math, super easy to calculate yourself with any calculator with sine/cosine functions. 

Takes maybe 5 minutes in a field book page. It's also a way to get on existing bearings. 

@mightymoe 

No arguments here, I don't have a problem with the math, my point was that in the context of this thread, there's not any question about how the software is applying the calculations.

I don't understand how one can eschew resections but have no problem with RTK/NRTK work where a proprietary algorithm is determining the measurements. There's more black-box to GNSS work than resections, so I don't get the resistance.

@rover83 oh you could hand calc a rtk vector it’s basic algebra and the cancellation of like terms but getting it into a readable format might take some doing and understanding of the message types and meanings. But I agree if understanding of what is going on and how to correctly apply it is all that’s needed. Most of the time. No doubt with your knowledge you could do it trust me.

It's important to distinguish between angle-only resections which were once prominent, versus angle and distance "resections" sometimes called free stationing. The restrictions for good accuracy are much relaxed when you have both angle and distance.