Hi Robert,
I am a senior site engineer managing the structural works packages. I work on London based commercial projects that range between ?50m and ?100m, so not exactly large scale projects that require high levels of surveying technical know how.
I've been doing this for 20 years (charted construction manager membership and civil engineering technician membership) and normally as long as the points all tie into one and other then if the initial GPS coordinates are say 20mm out then there is no drama, a boundary survey will be done in the same coordinates so the design is drawn/positioned to suit.?ÿ
I will carry on as normal, but I simply wanted to ask a few questions to learn how to improve.
Sometimes we would have the primary stations installed outside the site and I take it from there and bring in and manage the secondary control simply using retros with X,Y,Z.
Sounds like I need to do some YouTube least square training.?ÿ
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There is actually an answer to your original question. Simply, the answer is Star*Net by Microsurvey out of Canada. They are owned by Hexagon, so getting your original observations into the data stream should be relatively easy.
Buy the software, including GNSS and the translation modules. (You can actually get the full demo version for use for free for a bit, but the translation from Leica to .dat may not be available by demo.) Talk to the sales people. The whole company has a great reputation. They will get you moving forward. They want to make you a long term customer.
Watch the videos and go through the training on Starnet. Go through the whole thing. It is worthwhile simply in the education on how to balance control and traverses.
Run your observations through the software, and follow the steps you learned from the tutorial.
The whole process should take you about 30 hours the first time and about 2 the next time, and (if you have no blunders in your work) maybe 30 minutes thereafter when you work a project. And what I said is actually one of the great things about StarNet...it certainly helps you find your blunders.?ÿ
You can also use this on an ongoing basis for the site as you add in control, but be careful to "lock in" certain coordinates from your initial control so that you aren't moving what has effectively become your baseline (namely your original control).
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As you know, there is no bigger StarNet proponent than I. But do not assume that because Hexagon owns Microsurvey that they have any special access to the inner workings of Leica's raw data codes.?ÿ?ÿ
?50m to ?100m should be enough to justify survey grade GPS, which would tighten things up for you. It think that your initial coordinates will be a bit looser that 20 mm. Could be 20 cm. Nevertheless, I get what you are doing, and agree that it can be made to work.?ÿ?ÿ
I'd also say that such a project may not need a Phd level geodesist's touch, but the main thing is always to eliminate the blunders which are often the undoing of less experienced operators.?ÿ ?ÿ?ÿ
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LOL, you are probably correct, but they (used to?) have a conversion routine for the Leica raw data.?ÿ
@loyal?ÿ ?ÿControl is EVERYTHING. Did not think waving the sarcasm flag was necessary. I have done a pile of construct project control, leaving it up to the project manager is insane. Even projects with on site stakeout crews know well enough to (or to cover their butts) have real control set. Apparently, no interim documentation will be required.
I spend a lot more time on control than most. Monumenting it, tying it, adjusting it, documenting it, maintaining it. I've never regretted it, and believe that the time spent pays back many times over. I've done quite a bit of construction staking and never had any complaints about the extra time spent in preparation, and in fact have ha dcompliments about how I can arrive on site and get straight to it.?ÿ
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"It's not a large site, 65m by 170m, it's a residential complex with a 15 storey tower, so not exactly complex, therefore Instead of getting in and paying a surveying contractor I thought I'd give it a bash."
"I work on London based commercial projects that range between ?50m and ?100m, so not exactly large scale projects that require high levels of surveying technical know how."
SO ... 2 city blocks in one of the densest, most expensive cities of the world. I am pleased for the OP that he can consider such a project no big deal. If we (rule of thumb) figure the surveying cost at 1% to 2% of the construction budget we might be looking at the equivalent of $1,000,000 worth of surveying. What could possibly go wrong??ÿ
I'm reminded of the Record of Survey filed by an Arizona Structural Engineer with the statement that "Engineers are smarter than surveyors, and Structural Engineers are the most highly educated Engineers." Yeah, verily. That's a real thing.?ÿ I can't find a link right now, maybe somebody has it to post. It's a public record in Maricopa County.
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It's not a large site, 65m by 170m, it's a residential complex with a 15 storey tower, so not exactly complex, therefore Instead of getting in and paying a surveying contractor I thought I'd give it a bash.
Have at it Thomas. Really if it is not exactly complex, I see no reason for you to seek advice here. I mean I'm sure you will save a boat load of money by not having a professional do it. And since it is your first time and you are unsure of how you should proceed you will have the cash savings to use for correcting the items that are a part of your learning curve. Good luck.
All the links in this thread are stale, but maybe it will tweak someone's memory.?ÿ
See, here's the thing, as another non-surveyor sees it. It seems that you are intent upon taking your EDM measurements as gospel and just want to use the GPS points to get BNG coordinates for your points.
I assumed that you measured horizontal ground distances with the EDM, but we really don't know that. Are you sure that what you have are not slope distances or some kind of scaled distances?
That settled, you can use this site to convert your latitude/longitude GPS data to the BNG. You only have 11 points, so that shouldn't be too much work.
Coordinate converter | British Geological Survey (BGS)
You can easily calculate the BNG grid distances from point to point; it's just the Pythagorean Theorem. For example, the BNG distance from Point 1 to Point 2 is sqrt((Northing2 - Northing1)^2?ÿ (Easting2 - Easting1)^2), a quick and easy spreadsheet to create; one formula and a lot of copying.
But here's the problem. Your BNG distances and EDM ground distances aren't going to be equal. They differ by a multiplier: the product of the elevation factor and the scale factor. Just as forces and distances change when you move from a domed roof to a flat roof, geodetic measurements change when you move from an ellipsoidal surface to a lower plane surface. However, the ratio of each BNG distance to its corresponding EDM ground distance should be very nearly all equal.?ÿ
A least-squares adjustment would give you normal-distribution based statistics that tell you whether the differences you see are statistically significant or not.
In my humble opinion, you're playing with fire if you don't, at a minimum, get all of your measurements on the same coordinate system.
For a quick and very readable explanation, go here:
Thanks for your response.
Yes this is not a particularly large project and thanks for the information regarding London, I'm from London and worked in the construction industry in London for 20 years so I consider myself pretty experienced.
Looks like I have saved my company $1m on a lot of projects.
Control has now been set up as usual and all is well, as usual.?ÿ
Simply wanted a wee bit of advice to keep learning but got a load of opinions.?ÿ
@norman-oklahoma instruct "reginstered" surveyors? they aren't very well versed in spelling, though.
I'll probably go with overlaying the two surveys and tweaking to find the best fit.
This is often my approach to ??least squares adjustment.? ?ÿBut then, I am just a dumb dirt surveyor.
Looks like I have saved my company $1m on a lot of projects.
Control has now been set up as usual and all is well, as usual.?ÿ
Simply wanted a wee bit of advice to keep learning but got a load of opinions.
Imagine a licensed surveyor going on a structural engineers' forum and saying
"Yo guys I'm designing a pedestrian bridge 20m above a busy freeway. I have concrete and rebar, how do I put them together to get a deck? I've been just randomly sticking the rebar in and that's always worked before. I'm not a structural engineer or anything, but I'm a surveyor who has worked on bridge projects. It's just a multimillion dollar project, no big deal."
That's the equivalent of your OP. That bridge might hold; it might not. Whether it holds or not has little to do with the surveyor-playing-engineer's professional skill level and more to do with luck.
Same with your control - it might be good enough, it might not. Without knowing the goal of, or the positional tolerance of the project elements, it's impossible for us to say whether it will be OK.
The only thing we had to go on was you literally telling us that you don't know best practices, that you didn't think it was a big deal because it's "only" millions of dollars, and that you do this all the time so it shouldn't be difficult. You also threw out a couple of questionable procedures that might give you a result, but were not best practices.
You got the only advice that we could give you, which was, either learn how to do it properly or let someone else do it. Proper civil/structural design practice is a skill that takes time and training to learn. Guess what? Surveying is no different. Primary control for a heavy civil design project is pretty critical in the land surveying world, and mixing GNSS and conventional measurements properly takes skill and experience.
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I don't see many surveyors trying their hand at complex design, and certainly not broadcasting their ignorance of basic design procedures on an internet forum.
I do see plenty of engineers trying to play land surveyor. Sometimes they get lucky; sometimes not.
If you want to be good, not lucky, take some of the advice here to heart. If lucky is good enough for you, then carry on.
@rover83?ÿ ?ÿAs long as you have surveyed a few pedestrian overpasses and watched them being built, you should be fine. And best of all, since you are not a structural engineer, you don't need a permit.
The spelling is small potatoes compared to the tactlessness.?ÿ
