I started this post a couple of days ago (link below). I traversed some 12-year-old stations, and came up with some new co-ordinates for them which are up to 6mm difference from the original ones. The project is to set out some houses on a plot of land.
Should I re-issue the new station co-ordinates to the Architect and project manager?
From a practical point of view, I'm tempted NOT to issue the new station co-ordinates, because there will then be two sets of co-ordinates floating around for the same project which I think at some point could lead to some confusion and maybe an error.
I'm considering keeping the values of the new co-ordinates to myself. All the drawings will just have the original stations co-ordinates on them. My data collector will have the new co-ordinates entered which I'll use for setting out.
Think that strategy through completely. Regardless, there are now two sets of coordinates floating around. The old ones are in the hands of the architect and PM, you have the new ones.
Any check on your layout will reveal the difference, the issue will surface, and you will be on the defensive.
Withholding secrets on a construction project is rarely a good idea.
Any check on your layout will reveal the difference, the issue will surface, and you will be on the defensive.
Exactly.
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Published coordinates hold unless you can prove without a doubt that they're out. A traverse where you closed well may be enough if you're calling something off a foot, but if we're only talking a couple hundredths that isn't enough- you're now in network adjustment territory where you'll need to go back to the field to get additional redundancy.
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At the same time: does it really matter? What are you staking? Rough grade and utilities? Hardscape? Structural steel?
Check your reasoning here. There should be a one-to-one correspondence between point numbers and points. Two point numbers, two points, verified by the difference in coordinates for S1 and S1-1. It seems to me that you would be creating a pincushion, with all the attendant problems.
S1 and S1-1 are 6.7 mm apart. If that distance is a problem, then it needs to be reconciled. Trying to overcome it with point names, it seems to me, just creates confusion and magnifies the problem.
If you're the one doing the survey/layout, not sure why they need the coordinates.?ÿ
I'd just tell them I ran my control, checked into the prior control with decent results, and am using my own work for all layout, etc going forward.
If they want my control, I'll give it to them.?ÿ And as Nate said, mine will have new numbers.?ÿ No reason to provide anyone with the prior control points.?ÿ
Don't know about the UK, but here in the states, no architect I've ever worked for knew anything about coordinates
@mathteacher we had a party chief that did that for a primary control point for a stadium project (center of 50 yard line monument), and let me tell you this: DON'T DO THIS. EVER. Especially when you have subcontractors using the same points for layout.
Consider the fact that the traverse stations are 12-years-old. They could have definitely settled during that time. If the short backsight of your beginning traverse leg is troubling you, why not rerun the traverse in a different manner? Also, think about the purpose of your survey. Some people get so wrapped up with the numbers, they lose sight of the job. Are those 0.006 m and 0.003 m deltas you mention really going to make a difference in laying out houses? Structural steel, maybe, not houses.
Why do you feel your coordinate system is superior?
Find the longest possible straight line on the drawing and rotate your coordinates over to agree with those previous points.?ÿ Unless, of course you feel that line is inferior for some reason.?ÿ Play with it.?ÿ Find what rotation will give you the closest agreement on almost all points.
