One part the client loses, is the ability to overlay GIS data on top of topo data. Local counties have alot of free data.?ÿ When other surveyors are screwing up datums,?ÿ we all look bad.
We are all basically lazy. We do things a certain way. If someone does them, or wants them, a different way, then they must be wrong. (or, so too many believe) Say they want everything reported in feet and inches. We do it. Making a conversion requires us to do something we don't normally do. So what? Give them want they want and move on. Charge for your time to make the conversion. Sometimes the client only understands things one way and that is not your way. There is nothing inherently wrong with that.
How many times have you had a client ask you to take your data and send it to them but in such a way that they can work with it in their software which happens to be about six releases backwards from what you are working in? You don't insist they update to the same release you are using. You give them what they need.
I meant tight in regards to a representation of NC-Grid coordinates.?ÿ The site is around 600 acres and the three BMs they located were all along the southern periphery.?ÿ Even if they didn't mess up the conversion, I would expect that Grid coordinates extrapolated out a few miles would have some slop.?ÿ
NC spends a lot of time and money maintaining its network of physical benchmarks and CORS stations.?ÿ All surveys are required to have a tie to NC-Grid.?ÿ?ÿ
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It is very common practice here to scale grid coordinates about 0,0. While, yes, it isn't "correct" it does provide a replicable reference point for future work.?ÿ
Your issue has gone unnoticed because it doesn't matter. Your client is looking for volumes.
N10,000, E7,000, Z100.00
PLS - IL, MO, AR, KS, MN, KY
It is very common practice here to scale grid coordinates about 0,0. While, yes, it isn't "correct" it does provide a replicable reference point for future work.?ÿ
Nothing wrong with it IF the fact and the factor are supplied with the resulting coordinates. It is better to also reduce the millions and hundred thousands so people are alerted to look for that information.
that GIS data... is the base system well documented, all of it? Or is it a rubber sheet of garbled data using various "feet"?
It's gonna get worse, much worse.
thanks to Dr. Michael Dennis, National Geodetic Survey
https://www.ngs.noaa.gov/web/science_edu/webinar_series/fate-of-us-survey-foot.shtml
And that’s what I do. I have a blurb for my plats and table for the CAD.
N10,000, E7,000, Z100.00
PLS - IL, MO, AR, KS, MN, KY
If it's a scaled up SPC number then it should come along with a scale factor, origin point for the scale (typically 0,0), type and Epoch of SPC and points the SPC was tied too. Many of the older projects like DOT and local site projects predate any CORS. Site control points should be provided and held.?ÿ
DOT usually do it that way, normally they give you a spreadsheet and it explains the coordinate system. XYZ is the easy part if there is site control, the hang-up has mostly been elevation control when OPUS is pushed over good bench mark control.
There are at least two states that put out surveying books explaining the procedures to connect to DOT type control. I have one in the office, from control set-up to field to finish coding it must be 300 pages.
One issue is that some of these control projects came with metadata but over the years it got lost in an office, the old plant workers who knew what was going on left and new ones have no idea where it all came from.
That is typical with landfills, mines, railroads, ect.
And being tied to old SPS can be worse, I'd sooner have a 200' shift than a 3' shift where the 3' is actually SPC on the ellipsoid but might be NAD83/86.
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If I've said it once I've said it 1000 times. Friends should not let friends scale grid coordinates without truncating.
Very common here also. In fact, it was the Oregon DOT's stated policy for many years - until they instituted the current LDPs. LDPs rule.
I miss working on AKDOT projects.
Part of the deliverable was, and I assume still is, a Record of Survey that was solely a control scheme, called a Survey Control Diagram. Any and all monuments recovered, all control recovered or set (no "secret" control), any positional discrepancies noted. Complete with geodetic values including ellipsoid height, state plane grid values, and local ground values with ortho height and specific geoid used (if applicable). Complete with a site sketch showing all of the mons and control.
Datum and epoch tags, instrumentation and method of reduction - usually required to be networked adjustment by LS. Conversion metadata to go from SPC to ground and back again. Cap diagrams, descriptions including distance above/below ground and swing ties if possible.
This was recorded concurrently with any boundary ROS that the project required. Anyone following along afterward had everything they needed in those ROS docs. When you recovered a control point or a monument, you knew for sure whether it was referenced on the ROS, and whether it met positional tolerance.
While screwups certainly do happen, it's much harder to screw up when all of those items are required, reviewed by people who actually know what they are doing, and filed as public record.
With industry standard software it is just as fast to provide geodetic information on a smaller ROS or a simple plat or boundary line adjustment as it is with a ten-mile highway corridor survey. A few minutes to export the information, another few to drop it into a CAD program in tabular format. Adjust the conversion parameters and datum tags, and it's done.
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The other way to look at it is; what did the client contract you to do??ÿ If your contract calls for one thing, and now they want another, then you should charge for it.?ÿ If in fact they had a certain contract with another that was breached, and that costs them enough in fees from your contract, then they might go after the previous person for damages.?ÿ If it doesn't cost the client anything (or not much), then why should they care??ÿ If the client doesn't care, why should anyone else?
Generally, consumer protection is based on market forces.?ÿ In surveying, consumers continually get better service for cheaper rates, in spite of past errors and mistakes.?ÿ Until/unless past actions start costing them, or better service and product starts costing more rather than less than traditional methods, there really isn't any incentive (or reason) to go after anyone for less than desirable (but workable) results. And little incentive to pay more for someone with a better resume.
If the client changed after 9 years I imagine you might be giving them what they need, plus pointing out possible problems, plus solving for those problems, all for less than they're used to paying while avoiding any potential future harm from past error/mistake.?ÿ If that's the case you should have a contract clause that deals with this (especially if it's a common occurrence) that requires some set fee for conversions to alleviate past coordinate mistakes. It should be something serious like 5k-10k maybe. The ability to find and deal with these problems takes a lot of investment and knowledge, and is a valuable service to the client (but only if surveyors that know how say it is and charge a reasonable fee to do it).?ÿ
But it's tough, same thing happens with boundaries.?ÿ Recently had an attorney for my client who didn't think an expert was necessary for the court proceedings, and even if one was he could get a friend of a friend who was licensed to testify for no (or little) charge.?ÿ Eventually changed his mind, but like pulling teeth to do it.?ÿ He has no doubt now that he has the resulting report, but assumed (like most) that all surveyors are equal on all things, and any two will get different but equally justifiable results (just a matter of personal judgment ya know), or if same results any two can equally describe the reason why.?ÿ The surveyors license seems to be something (at least in this area) that you can't live down, no matter how good you get at what you do. It just comes with this almost indestructible stereotype of lack of intelligence, education, and hence worth of service. I've come to believe it's something only the market can take care of (or not).
I think the most likely source of this "error" is not from scaling, but from an autonomous position from back in the days of Selective Availability, that was never reconsidered when SA went away.?ÿ If the landfill has been in operation for more than 20 years, I suspect that to be the source of the current confusion.
We sold a Promark 2 system to an outfit that monitored an watershed close to 20 years ago.?ÿ They had a favorite control point that they had been relating everything to.?ÿ There are 8-10 other points around the watershed that had control positions established by GPS.?ÿ We got the system back because when they processed their data on the whole set of control points, holding this favorite piont at the northeast corner of the project, they?ÿ missed all the other points by a bit over 3 feet.?ÿ Interestingly, when you held any other point, all the others checked within the range of reason, say no more than 0.05' horizontally, except for that northeasternmost point.?ÿ It was out 3 feet.?ÿ?ÿ
But they were all about 140 feet different than a post-Selective Availability autonomous position.?ÿ I beleive that to be the source of your bust.
That makes a lot of sense, the error was random and could be very well 190'. Those were the days, nothing much could be done without RTK.
Please correct me if I am wrong, but weren't carrier-phase measurements and relative positioning, such as surveyors would have used in positioning of control networks prior to 2000, immune to SA degradation? I started my surveying career a few years later, but I was under the impression that dual-frequency carrier-phase receivers were industry standard by that point precisely because of this.
Whether or not the "held" position was autonomous, all the other control points should be correct relative to that one if standard survey equipment was used and proper procedures followed.
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ETA: I have processed a lot of L1-only static projects as well for smaller jobs <10km. I believed that the only difference between pre- and post-SA L1-only work was the length of observations due to the increased random variation in each position throughout the session. Is that not the case?
I do not have the experience to correct you, right or wrong. My experience with GPS before joining the Hayes Instrument Company team in October of 1998 was pretty much limited to how to spell the acronym.
I may be wrong too, and subject to correction, but I was unaware that the type of equipment had any effect on SA applied to GPS positioning.
If the control was established in 2012, must have some off a monument that did not have precise horizontal coordinates.
Not the case here. I'm told the control was established in 2010.
It's somewhat comforting to know that Dufus & Goofus are alive and well, and continuing their quest to spread their wisdom around the county.
🙂