Recently I did a year-end topo of a Land Fill. A local surveyor was supposed to map this project on NAD83 in 2010. They have performed year-end topo's for the prior 8 years. By comparing aerial imagery, OPUS and RTN, it is very clear that there is a 135ft horizontal shift.
The Landfill has too much historic data to correct this, so they want me to adjust my data to the pseudo NAD83 historic datum. Sure I can do this, but I hate to.?ÿ
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I find problems like this a lot, and there are never repercussions on the error made by another surveyor.
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I feel they should pay for the gross error, not sure how.
Not sure what kind of cost the owner has incurred for which compensation is required.?ÿ Everything in this world is relative.?ÿ We simply install false frameworks to describe our world to satisfy certain interested parties.?ÿ But, that is all they are, false frameworks.?ÿ It doesn't matter if we call it zero C or thirty-two F, it is still cold.?ÿ It doesn't matter if it longitude west of Greenwich or Washington D.C., the intent is the same.?ÿ It doesn't really matter if the finish floor level is 100.00 feet (assumed) or 1124.74 above MSL.?ÿ The job standard may call for meters or feet and inches or feet and decimal feet.?ÿ It doesn't really matter.?ÿ All that really matters is that everyone working together gets on the same page.?ÿ No one's page is necessarily better than another's, so long as everyone uses whatever the local standard happens to be.
The landfill data probably needs to be on datum for permitting and resource tracking. Adjusting the control to datum could easily be integrated to your annual workflow. Transformation of legacy data could be automated and performed as needed.
These little 'time-bombs' are everywhere. The client will be happy with the person who identifies real problems and solves them efficiently. Focus your energy there rather than on the prior professional.?ÿ
Is it really NAD27?
I see this kind of stuff much more often than one would expect.
Signed/Certified "Coordinate Listings" BOLDLY stating that the Coordinates are "NAD83 Whatever," when in fact they are "kinda/sorta/more-or-less" NAD27 Coordinates that are "kinda/sorta/more-or-less" scaled to "ground" (or not).
On small (postage stamp) projects that only cover a square mile or so, one can usually come up with a good solution, subject of course to the level of internal spatial consistency of the original data. But when the areal extent of the project gets into the several dozen (or hundred) square miles, things usually fall apart pretty fast.
Bottom line is, trying to polish turds is usually a big waste time, although sometimes that IS THE JOB at hand.
Loyal
Not NAD27, around here there is about 500,000ft in the easting between 27 and 83.
Not NAD27, around here there is about 500,000ft in the easting between 27 and 83.
Yes, not the wrong SPC.?ÿ But how far is it between NAD27 and NAD83 for the same lat/lon numbers??ÿ Like, take a NAD27 lat/lon and convert it to NAD83 SPC? And mix in some grid/ground factor.
Possibly NAD83 scaled to ground? If so that is not so much a mistake but rather a failure in communication.?ÿ
I'm not interested in how the error occurred. It is amazing this error went unnoticed for 10 years. A simple check would have identified the error.
I would not consider scaling grid to ground in this manor a mis-communication, that is just wrong. If they wanted ground coordinates it shouldn't be any where close to SPC.
I'm not interested in how the error occurred. It is amazing this error went unnoticed for 10 years. A simple check would have identified the error.?ÿ
The obvious answer is:
That is an opinion - one we share.?ÿ But not everybody does. It has been a common practice around here.
Looks like they tried to scale SPC grid to ground at 0,0.
I wonder how many projects they screwed up, since this was done in 2010.
If there is sufficient control to reestablish what the previous surveyor did, it may he an error, but it's an error like using there instead of their. It looks pretty stupid, but everyone knows what you mean.
There is usually marginal benefit to the client in using state plane versus a random recreatable system.
Most older "grid ties" to monuments in my working area will have some kind of screw up in calcs or coord. conversions or they just use NAD 27 because they didn't want to bother with converting meters to feet, etc.
It has improved with the statewide RTN and affordable network rovers.
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I have a similar situation at a landfill.?ÿ I don't understand why their coordinates were 101' SW of GRID. They traversed through three NCGS benchmarks so it should have been closer. No GPS was used so it never would've been tight.?ÿ
I'm going to wait for the implementation of NATRF2022 to fix it. Until then I will just continue dumping my data in a spreadsheet to convert it back to the wannabe State Plane coordinates when needed.?ÿ
My guess is that a CAD tech messed up and the PLS didn't catch it.
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A total station trav should be tighter than an RTK survey.
We are working on a landfill where the work done to create everything is based on NGVD 29.?ÿ The delta to NAVD 88 is roughly half a foot at that location.?ÿ Everyone involved is perfectly content with using the 29 figures for determination of key elevations because that matches their design information.?ÿ WE KNOW what we would like to report, but, like your client, they are happier if they don't have to think about it.?ÿ So, we make statements about certain locations being so much higher or lower than the information provided in the design information.
That's why they invented the term KISS.?ÿ Just keepin' it simple.
While I understand your point, I also understand why the client would request having the survey completed in NAD83. It saves everyone else who surveys on the site from having to invent their own false framework by trying to match the initial, non standardized false framework.
If you're paid to record temperatures in Celsius along with your NAD83 survey and you submit temps in Fahrenheit, Kelvin or your own units you did it wrong.
