Some times that is an option. Many times it's not. I'm not about to drive two hours back to the office to comp something, scale and rotate it and drive two hours back to start my search when I need to get the job done there and then because I've got five other jobs about to run me over and construction crews and engineers that don't appreciate being told to just hang out until I get my act together. I jam a year's work into eight months and the pace at times would make your head spin. I didn't have single gray hair when I started. Seven years later I have hardly a hair on my head with any color.
The State Cadastral/GIS people are thrilled to death to get an OPUS LLH/Ellipsoid height reported on any survey. The majority they get don't or are all gobbed up in one way or another. For the most part the GIS people have had to rely on ties to the rectangular system which is based on old NAD27 values later converted to NAD83. The old NAD27 values weren't all that great to begin with.
> Some times that is an option. Many times it's not. I'm not about to drive two hours back to the office to comp something, scale and rotate it and drive two hours back to start my search when I need to get the job done there and then because I've got five other jobs about to run me over and construction crews and engineers that don't appreciate being told to just hang out until I get my act together.
Well, "basis of bearings" to me means the information with which I can calculate the exact direction that you reported as running on some stated bearing and that will when run out on the ground lay right upon the line you described, subject only to the (presumably) small random errors in your work.
When the basis of bearings is grid North of a standard map projection, the entire problem disappears because you have declared the independently reproducible basis for following the directions of lines you report. When the basis of bearings is some spur-of-the-moment-projection-in-the-RTK-controller, you have to burden your survey with a load of otherwise purposeless metadata that would otherwise be avoided by using standard projections.
Are you referring to t-T? The rate of change in Convergence changes significantly depending on latitude. Also it is important for determining the difference in convergence for two different systems (such as State Plane and LDP).
Question, if you localize from grid to a local project datum, how can one still say north is grid?
> Are you referring to t-T?
No, I'm referring to the practical fact that the poster is surveying small areas from an RTK base that presumably is within radio range. So it is unlikely that knowing the exact actual latitude of the RTK base will produce a significantly different answer than would be had by assuming it to have been at the average latitude of the project.
<Donned my flame retardant undies for this statement.
I smell smoke...you should have paid for the upgrade.
I'll sing a song and cheer everybody up.
(musick...
I'm going to leave
Ole Texas now
They have no use
for the Long Horn Cow
I'll say good by
to the Ala Moe
And hit that trail
Toward Mex e Ko
(... static...)
I'll eat my bread
and my sar deans.
... ^C musick end)
> <Donned my flame retardant undies for this statement.
>
> I smell smoke...you should have paid for the upgrade.
It's really quite alright. My patent asbestos undies held up just fine. My immediate work area is bigger than most of the States some of these jokers live in and straddles two different State Plane zones. You could fit two Texas's into this State. Give me a lat/long tied to CORS and approximate elevation and I can put that plat data into just about any projection I like as long as I don't plan on covering too large an area. We just live in different realities and I understand their logic, has it's limitations.
Based on Kent's and Paul's attitude? Those two can kiss my Alaska white a$$. And that, is all I have further to say on the matter. 😀
"I" Before "E" Except After "C"
I have noticed that some of the older, prolific and frequent posters here are overly didactic. It it a human trait or flaw.
Sometimes the ones with the most to say really have the least to say but think that everyone needs to listen to what they have to say.
Look at the stats for top posters and you will get my point.
> Not sure why you feel it necessary to nominate what gear and software was used.
>
> To my mind you only write down the info that is useful to others.
Agreed. "THIS SURVEY WAS CONDUCTED USING SURVEY GRADE (MAKE/MODEL) RECIEVERS [sp]" is redundant; delete the "SURVEY GRADE" verbiage. Stating the software type and rev. is useful as there may be a bug in that rev. that bollixed the results and can be unsnarled later by others.
Personally I'd never use RTK and OPUS to control and orient a survey that required high geodetic accuracy. Much better is to occupy nearby published 1st order stations to create quality 2nd order project control, static or fast static and do a network adjustment holding the 1st order stations.
But that's just me, in a locale with lots of handy high order physical control nearby. Inclusion of nearby CORS stations (<20km) is acceptable too, but an RTK single point translocation from OPUS stations hundreds of kilometers from the site to establish position (and especially orientation) gives me the heebee-jeebies. I understand, though, most clients balk at the inclusion of a line item for two days of 4 receiver static (or fast static) leapfrogging observations. So we cowboy with a morning of RTK and OPUS without touching tight nearby control and usually get away with it. *Usually* is the operative word here, folks.
This is another thread to be archived (remember, I'm gathering material for the second edition of my 3-D book). The original post is legitimate and many of the comments are quite good. There are also some amusing comments - that's OK by me. I enjoy them.
I don't have "Closure" on the issue but I refer the serious reader to:
1. A peer-reviewed paper on the issue and posted FYI.
2. A working document developed in concert with our City Surveyor also posted.
3. An actual example developed by/for a class at NMSU likewise posted. Suggestion - carefully review the bearings on the plat.
As a reminder - don't forget:
1. Meridians are not parallel.
2. The forward azimuth and the back azimuth differ by 180 degrees +/- convergence.
3. Grid azimuths are referenced to the true meridian through the P.O.B.
The global spatial data model (GSDM) accommodates all points made above.
Stay tuned for more information or see http://www.globalcogo.com
Upon reading the post I realized I should have stated that grid bearings ARE different by exactly 180 degrees.
I tried to "edit" the post but forget how to access that option.
