@norm Oregon DOT (ODOT) had a visionary chief of surveys, now retired who championed LDP's because of the exact issue you mention. We now have something like 40+ zones covering the state. You can have a true geodetic based grid system with low distortion, no scaling, rotation, truncating; just use it as is. All the metadata and defining parameters are published and it works the same as a SPC zone in your favorite software, you just note the zone in your metadata on your survey. Everyone then can be on same page, no guessing about what was or wasn't done.
SHG
@shelby-h-griggs-pls yeah but it says ??WGS84? on my confuser screen. 😉
(I learned the word ??confuser? from a ground school instructor in 1989 in reference to our E6B computer).
I no longer live in the world of SPC.?ÿ WGS 84 (G1762) all the time, in all that I do. I don't miss these conversations.?ÿ
How are you doing this? Other than the "here now" position there is nothing broadcasting WGS84 positions nor are there any WGS84 positions on monuments outside of some DoD installations. Of course the associated epoch of ITRF is available via OPUS, etc. and that is closely aligned to the corresponding WGS84 epoch. If you are pulling off an OPUS report the ITRF data and using that as a basis, then you really are using ITRF and NOT WGS84, although the difference is small.
Even if you are using ITRF or WGS84, then what are you using for a grid system?
The issue isn't what underlying geodetic system you are using, either "WGS84", ITRF, NAD83, etc., the issue is then getting grid coordinates on a non flat earth. You have the same issues no matter which geodetic system you use.
With rare exceptions, i.e. a DoD project where you may have access to WGS84 monuments, no surveyor should be reporting that the basis of survey is WGS84.
SHG
I bet he works somewhere that has what is needed to do this. ?ÿI use to work in same place. ?ÿ
I've surveyed in State Coordinate System coordinates once in the last 30 years. It was a PITA. The company I did it for had no ability to use them. From the beginning to the end of the project is was one mess after another.?ÿ
The weird thing was that company had senior engineers and surveyors who were well versed in the DOT systems but they retired just before the project.?ÿ
Here is an scenario I ran into.....
I do feel your pain. Incompetence is everywhere.
We used the work Ron did as a guide. We only need 14 zones thakfully.?ÿ
Until recently I was all fat and happy in my keenly developed LDP.
CURRENTLY?ÿ I'm really working my brain again to pay attention to each project as we work in different SPC, different geoids, and yeah, I'm working harder than I was them in my LDP.
I cry a little while sipping on my bourbon, careful to not drop any tears into the glass and spoil it....
???? ?????ÿ
Whether a project is "in state plane" or not, publishing geodetic coordinates along with detailed coordinate system metadata goes a long way toward allowing anyone to work with any of your data in any way they see fit.
@rover83 rare to get metadata or LLH so one can maybe deduce what happened. I worked on a project once where major amounts of documentation were provided, the issue was "the here now" coordinates were shown as LLH and the Grid coordinates were correct. No scaling or anything, BUT It took me a long time to figure out why I couldn't get from the provided LLH to Grid.
Sometimes what folks don't know when providing data and reports is scary.
SHG
@olemanriver Right, I (we) don't use SPC.?ÿ It's all on a global scale.?ÿ
What about this old math no one I have ever even spoke to in last few years. But the corrected ZA for the difference in height of instrument and targets. ?ÿNot elevation difference just target heigh and instrument height difference to correct ZA to calculate the correct HZ distance. ?ÿMost dc do all of this now. ?ÿOn flat ground for most work no problem. But traverse up a mountain and reducing all the hz distance to a common plane is seen if you dont. ?ÿ Well time for me to finish a topo talk at y??all later. ?ÿ
different geoids
Are you working on legacy projects? Or contracted to use a specific geoid?
We're lucky that around here, 12B and 18 are usually close enough?ÿ that the difference between them is well under the modelled error. Combine that with typical RTK accuracy and we never see that 1-2cm.
@rover83?ÿ
Yep, legacy and carry over.
I'm telling ya, I was spoiled and really miss my LDP!!!!!
It's a good work up for my brain again to get engaged and involved with the process of moving the process along for the 2022.
Either way, keeping the brain flexible and strong overall is a good thing as long as you're not wasting too much time or money.
