Linking cad dwg to control station coordinates

beware...it's not always that simple and never, ever, trust a CAD file to be correct.

Where are you getting the control information from??ÿ The days of taking the survey base map and shifting and rotating to fit a sheet set are long gone for the engineer's I work with (architects still see to like to scale by 12 though).?ÿ That being said, the control and design files are in the same system in their cases.?ÿ I'm not going to say that is a truth, so you need to check with the engineer.?ÿ If the coordinate systems are not coincident then someone needs to provide you with the parameters.

As for the drawing itself as @stlsurveyor said, you need to check the drawing for correctness before you rely on it.?ÿ?ÿ

The fact that you are seeking guidance here suggests that you are a smart person. You've undoubtedly got solid math/trig skills. You are approaching the problem logically. Here's 2 pence worth of perspective to add to the equation when working out this problem:

As long as it doesn't matter if the constructed features are in the planned location and you can absorb the cost/time of a demo/rebuild and you can afford to compensate adjoiners if you happen to impact their property, then this is definitely something you can take on without the traditional education, experience, and testing.

If you have the time, it would probably be less expensive to complete a 2-4 year survey program and work for a qualified surveyor for a number of years than it would be to stake a modest priced building in a critical easement, within setbacks, over the property line, or on another lot/tract.

I genuinely respect your desire to do it yourself - many on this board have that same personality trait. You may be able to pull this off (that would be good luck) or you may create some significant financial damage (that would be bad luck), you probably won't know for sure until some time (possibly years) after the cement is dry. Get the training you need and build your skills on work that doesn't have the financial risk of construction.

(And... in the US it's highly unlikely that your liability insurance would cover you if you stake something wrong unless you have professional liability insurance specific to surveying - I suspect the UK has similar limitations)

If you:

• don't have the time for education and experience, or;
• don't want to hire a qualified surveyor, or;
• don't really care if the improvements are in the designed location, or;
• have plenty of money and simply want to do it yourself now -

go for it!

Respectfully

Answering this gives me pause. Are you a new surveyor working with others data for the first time? Or are you a grunt in an office and afraid to ask the boss for info on something you told him you knew how to do? Or you could be a contractor, looking to bypass a surveyor and want to put a project into your GPS and actually build something beyond your experience and knowledge?

If it is one I would gladly help you, if it is two, whatever I say could be contrary to standard office protocol, if it is three I care not to be near a fiasco.

Check, check and then recheck. I have seen surveyors pay lots of good money because the staked out a drawing project that was bigger than the actual lot. In other cases of drawing incorrectness I have helped contractors by informing them of architect/engineering errors. They got their money to fix those errors before they were built rather than arguing after the fact to get the proper reimbursement. Everything from project baseline errors to foundation plans, that put beams farther apart, than the girders designed to span them. And without a signed and sealed copy in your file you are on the hook for more money than you are worth.

Paul in PA?ÿ

@marc

This subject "Linking cad to ctrl coords" has been the source of many many errors, assumptions, train wrecks, late night head scratching, and general consternation, by surveyors, who KNOW what they are doing. You look for, and want simple answers, so you can .... Stake out stuff! This is where the liability is. Engineers are notoriously bad about pulling stunts, such as rotating the Survey, so the E-W street, is due E-W, so they can design a rectangular building, on a lot, whose sides are NOT parallel, and whose front and back likewise are not parallel.?ÿ

So, how do we help you?

Did you know that "north" is just a general concept? You can have 10 genuine, and good surveys, showing the SAME line, with different bearings, that are all different from each other, by 5 and 10 degrees, or more?

Did you know that some coord systems need scaled, to be placed on the ground?

I honestly suggest you go to the source of your plans, and the source of your control coords, and learn all you can. SOMETIMES, these sources can Both contain types of errors, that will throw you, and you really do need to be able to spot it, and deal with it in a practical way.

I did const staking at o'hare field, in Chicago. The engineers plans were full of errors. We had to modify them all the time. Stake a taxiway light, and it landed on an electrical box. What did we do? Slid the taxiway light parallel to the taxiway, 15 feet, and sent a note and a pic to the engineer. By the time the engineer got it, the concrete on the light was dry.

Yes, there's liability. But, that's what we do.

Welcome to our table.

Nate

?ÿ

My fellow surveyors have all given you excellent advise but there is one more thing you need to know. If you are going to survive in this kind of work. It is not to be timid. If you do not have a set of brass balls or ovaries and it is not the size but the purity of the brass that matters. Then you are done.

Really, we aren't TRYING to be mean, exclusive, knotheads, or otherwise avoid "giving you a simple answer".

We have been THROUGH the experience, of tearing out our own hair, being frustrated, talking some really bad language, so bad, that engineers have to plug their ears. You have asked for a lot, but you don't know it. Some projects are built "right". They have a good control network. A good design, built on this ctrl network, etc. But, most are not. When the ctrl network, and the engineering plans are NOT on the same datum, (rotation, scale, and translation, and elevation), then you must derive these numbers yourself. It can get real sticky fast. You absolutely must have a handle on all this. We cannot give this to you. We'd have to monkey with it, until we were confident. There are several thousand possibilities here, and we'd be selling you down the tubes,?ÿ to try.

If you do hire a surveyor, you'd do well to carefully hire one that's FAMILIAR with this. Not all surveyors are familiar with it.

It could be a simple job. But, you could discover ITS NOT, 1/2 way through.... And that's a real rub.

Thanks,

Nate

There are too many polite people in this forum.That's fine, except that Marc is in some serious trouble.

Sorry Marc, but if you need to ask these sorts of questions then you are going to get sued.

When people ask me what a "Surveyor" actually is, I tell them that we either:

a) receive 2D info from architects, engineers or other designers and mark out that info in a 3D world, or

b) record locations of our 3D world and put that info on a 2D plan for architects, engineers or other designers to play with.

Transferring data from a plan to the earth (or vice versa) is one of the most fundamental things that a Surveyor does.

The "science" is converting from 3D to 2D while the "art" is hiding all the errors. Both require significant training.

Judging by the questions that you have asked in other threads, you are neither a Licensed/Registered Surveyor, a Surveyor of any other form, a Survey Technician, an assistant of any of the above........

If you can't choose your own azimuth and local coordinates, then figure out how to scale and rotate your CAD drawing onto your local datum, then you are missing something fundamental.

If someone gives you a plan that says "put this mark on the ground 3 feet/metres away from this thing over here", but you can't make that plan relate to the earth's surface correctly, then you are going to make a mistake that will destroy you. Alternatively, if you get this job right and the next job requires an arc-to-chord correction or is ON datum, then you're finished.

I'm guessing that have no insurance either? If by some miracle you do have insurance, and you inevitably make a mistake, then you need to remember that the insurance company will have some sort of Surveyor floating around who will figure out what you have done.

Insurance companies are in the business of taking money- not giving money.

If you don't know how to set up local control (without tying into any sort of national grid) then you clearly don't understand WHY you would need to do it on a mathematical level, which means that you don't know how to triangulate, which means you haven't studied trigonometry properly, which means you shouldn't be doing this.

Pack up your total station, then go and do a Surveying course. Seriously.

You.

Are.

Going.

To.

Get.

Sued.

Guys, we've all studied for years and worked for years. We all know that mistakes happen and we all know how much those mistakes can cost when things go sideways.

We should NOT be encouraging people like Marc.

The basic problem you have is there is no one set of proceedures as every situation can be present a unique set of challenges. It's not a souffl?? where you can follow a recipe and if you do everything right the outcome is predictable. You need to be capable of evaluating all of the parameters, determine where all the issues are, often multiple layers that may or may not be interdependent, ?ÿand then come up with the unique recipe for a succesful outcome. As far as I know, nobody has yet published 'The Surveyors Cook Book', though there are many books on the subject.