Surveying questions

[adm_geomatics]

Please elaborate on this point.

My experience with what I think @JFlamm is mentioning is the fact that in construction we have PLS control sheets in the contract documents and the Contractor is held to +/- 0.10ft for general site work that can be tied back into those benchmarks and those benchmarks alone. We have to ask for additional benchmarks or at least a local benchmark on pretty much every project because they may supply two or three in the plans but near always one or two will be missing. The Contractors in turn hold the Drone Service Providers to these tolerances and we are seeing more often now that when a DSP is working with a larger Contractor or Surveyor they are being required to claim the accuracy in their documentation or they are writing a subcontract.

 

[JFlamm]

My experience with what I think @JFlamm is mentioning is the fact that in construction we have PLS control sheets in the contract documents and the Contractor is held to +/- 0.10ft for general site work that can be tied back into those benchmarks and those benchmarks alone. We have to ask for additional benchmarks or at least a local benchmark on pretty much every project because they may supply two or three in the plans but near always one or two will be missing. The Contractors in turn hold the Drone Service Providers to these tolerances and we are seeing more often now that when a DSP is working with a larger Contractor or Surveyor they are being required to claim the accuracy in their documentation or they are writing a subcontract.

You are correct but I'll take it a step farther. Control isn't just some arbitrary point in the ground. Control has to and will have a relationship to the parcel boundary. We surveyors create that relationship so architects and engineers can keep their designs between the lines. Lines being boundary lines, right-of-ways, easements and building lines. We then either pass along that control information or use it ourselves to put those plans to real life. We have state statutes with standards of precision and accuracy that we have to abide by when we perform and deliver those surveys. That's why we are the only ones that can legally do it. That's the 20,000' view of it anyway.

 

[Dave Pitman]

Control has to and will have a relationship to the parcel boundary. We surveyors create that relationship so architects and engineers can keep their designs between the lines. Lines being boundary lines, right-of-ways, easements and building lines

Okay, got it. I was unsure if you were referring to using an RTK network for implementing an RTK or PPK workflow. But I didn't think that's what you meant.

If drone ops, even those that know what they are doing, color within the legal lines and make it clear in the deliverable that that is what is provided. And, "some survey boards" accept that they are perhaps loosing some of the work they used to take for granted. (although nothing is stopping them from doing the work for less $$ than they used to get away charging in order to keep the work). Then we can all co-exist. I have worked with surveyors that totally get this and are making it work by either getting onboard with their own uas program, or hiring us to provide data on appropriate projects so that they can leverage the $$ savings over doing terrestrial collection only. And I have also run into the surveyors that are adimatly against any use at all other than by them.

 

[adm_geomatics]

You are correct but I'll take it a step farther. Control isn't just some arbitrary point in the ground. Control has to and will have a relationship to the parcel boundary. We surveyors create that relationship so architects and engineers can keep their designs between the lines. Lines being boundary lines, right-of-ways, easements and building lines. We then either pass along that control information or use it ourselves to put those plans to real life. We have state statutes with standards of precision and accuracy that we have to abide by when we perform and deliver those surveys. That's why we are the only ones that can legally do it. That's the 20,000' view of it anyway.

I understand the point of establishing dedicated control to a parcel but in the Engineering, GIS, Construction worlds in Texas it's the opposite. The control is geodetic and derived from NGS and local traverses establish "site" control and the boundary is geographically located according to that. Rarely when I was doing LT Surveys would we ever have a geodetic point. Just set a 3-point resection and shoot in what's there. Our control could be re-used by a subsequent survey but rarely was that information ever passed along back in the day. Now everyone uses GPS to localize but it's not consistent and rarely can you two properties together from different localizations.

 

[JFlamm]

I understand the point of establishing dedicated control to a parcel but in the Engineering, GIS, Construction worlds in Texas it's the opposite. The control is geodetic and derived from NGS and local traverses establish "site" control and the boundary is geographically located according to that. Rarely when I was doing LT Surveys would we ever have a geodetic point. Just set a 3-point resection and shoot in what's there. Our control could be re-used by a subsequent survey but rarely was that information ever passed along back in the day. Now everyone uses GPS to localize but it's not consistent and rarely can you two properties together from different localizations.

That's interesting but not surprising. It's not wrong either. Horse-Cart, Cart-Horse. It gets the job done. I've done plenty of preliminary studies that way. Once the project is deemed viable, we go back and perform the boundary survey to tie everything together.

You can have assumed control coordinates (ie...5000,7000,100) or you can take it a step farther and tie into NGS or GRS or Network VRS via GNSS if you want to geolocate the site to the real world. Just like you said, then the boundary is located from that control network to place it in the reference system needed. There will always be a tie-in to the boundary. That's the surveyor's job. Designs, plans and mapping will always need a spatial relationship to a boundary, right-of-way or easement to keep things between the lines. What coordinate system it is, doesn't matter. You can map 1000 acres of woods with your RTK drone but you won't know if you mapped my 1000 acres or his 1000 acres or 800/200 until you create a spatial relationship to the boundary. That's a bit to the extreme but you get my point.

Here's another thing, property boundary information will NEVER have a definite real world coordinate attached to it. It can remain close but never definite. Boundary law and legal principles have coordinates last on the list of boundary evidence for a reason and that's because things are always moving. Think California for a more aggressive example. Evidence and Procedures a lot of times doesn't place a missing corner right back in the exact position intended. That's what the PLS gets paid for to figure out. More on that at RPLS.com.

 

[Midwest Aerotech]

After reading extensively on this topic, the way I read an appropriate response is "follow the dollars".