MightyMoe, post: 347616, member: 700 wrote: Ok,,,,,,,,,,,,,you do realize that I'm discussing two OTHER surveyors (well one surveyor and one engineer) who both surveyed a section, completely unrelated to ANYTHING I'm doing besides reviewing the results. AND I'm showing what a good job they BOTH did.
In fact the engineer brought in photos of all the monuments, he located them twice just like I've asked him to, and he is a very good surveyor, I can't imagine anyone I would rather have topo and design a site or road. Or stake one, he really knows his stuff.
The DAF issue is just relating that while they both came up with different numbers it doesn't disregard ANYTHING they BOTH did, nor does it make either survey different in any meaningful way.
The extra long DAF is an unnecessary computer generated number that he doesn't do anymore, cause he got tired of messing with it, as you can see the surveyor already knew better.
Again, the point isn't that you are incorrect in your statement. It's to remind folks that those 'useless' digits can impact a lot of common work flows. Around here if you use the inverse of the DAF (as required by some software) and drop those digits it will matter. Distances will be fine but coordinates will shift feet. I understand that a standalone project won't be impacted, but any sort of data sharing and archiving will.
I thought the standard NAD27 CSF was 0.99995
Grid/CSF=ground
I agree that once the number is picked you are stuck with it.
The engineer sat on a control point a few miles northwest of this section and let TGO calculate a number for the Ground Scale Factor which is what TGO calls it. Then he applied it to his entire project, of course the number is valid only for that particular point.
He then put state plane on that control point and expanded his coordinates around it using the long number.
Now he and I are using the long number since it's set into the job.
What I do and what most do is try and pick a number that works across the entire area, a mean if you will.
So truncating it at six places has become generally accepted.
As far as the coordinate issue, since he is expanding around a near point the 6th place would work ok, 7 would be better, 8 total overkill.
DOT expects 9 places so when I do one I will just publish a number like 1.000294000 and they are quite happy with it, it fits into their standard spreadsheet...............
For this work only state plane coordinates are being published, the number is only applied to the distances on the plat.
Following the other surveyor in the goofy lambert system up north,,,,,,,,it looks like he is applying his DAF on a township basis, which is kinda ingenious I think.
Starting on the south he is about 1.0001 heading north he ends up about 1.0007.
I hadn't thought of doing that, but I have to say its a great idea.
MightyMoe, post: 347711, member: 700 wrote: I agree that once the number is picked you are stuck with it.
The engineer sat on a control point a few miles northwest of this section and let TGO calculate a number for the Ground Scale Factor which is what TGO calls it. Then he applied it to his entire project, of course the number is valid only for that particular point.
He then put state plane on that control point and expanded his coordinates around it using the long number.
Now he and I are using the long number since it's set into the job.
What I do and what most do is try and pick a number that works across the entire area, a mean if you will.
So truncating it at six places has become generally accepted.
As far as the coordinate issue, since he is expanding around a near point the 6th place would work ok, 7 would be better, 8 total overkill.
DOT expects 9 places so when I do one I will just publish a number like 1.000294000 and they are quite happy with it, it fits into their standard spreadsheet...............
For this work only state plane coordinates are being published, the number is only applied to the distances on the plat.
Following the other surveyor in the goofy lambert system up north,,,,,,,,it looks like he is applying his DAF on a township basis, which is kinda ingenious I think.
Starting on the south he is about 1.0001 heading north he ends up about 1.0007.
I hadn't thought of doing that, but I have to say its a great idea.
We precompute the township average prior to the site visit. It is either used directly in the data collector or used as the basis of a new projection. I like work flows where the crew arrives, checks in and goes to work...
I wish everyone did it the same way you do, the work flow is much simplified then.