The datum thread by Jerry below made me think about the recent plan datum statement I ran across. 
That's even better than my all time favorite "BASIS OF BEARINGS GEODETIC BY GPS"...
I'm embarrassed to be an Iowan. I can only hope the plan was prepared by someone from Wisconsin.:-D
damn that's frustrating
Almost as bad as the Basis of Bearing being Astrodetic North 😛
Or maybe they're actually confessing to running 'grid on ground'...
> That's even better than my all time favorite "BASIS OF BEARINGS GEODETIC BY GPS"...
hmmm. I'd definitely prefer more information (such as Geodetic at some geographic point or truly geodetic, and by what means of GPS positioning), but the statement isn't technically wrong.
> Almost as bad as the Basis of Bearing being Astrodetic North 😛
>
> Or maybe they're actually confessing to running 'grid on ground'...
Maybe they used the local vertical 😉
Reckon I should've read it a little closer, there was actually something else about it that cracked me up since I work with projections quite a bit...
Forgive me for being ignorant, but isn't a basis of bearing to be between 2 found (or set) monuments. Thus it can be duplicated without any questions. Who cares if its an assumed North?
There is a guy around here who just hooks up his GPS, hits the "here" key and goes. His basis of bearing is "WGS 84", whatever that is.
Sad....
Well that is simply the Geonomic with the Plalace correction unapplied. 😛
> Forgive me for being ignorant, but isn't a basis of bearing to be between 2 found (or set) monuments. Thus it can be duplicated without any questions. Who cares if its an assumed North?
>
It can't be duplicated if all but one of the monuments is destroyed. It can't be conveniently duplicated if all but one monument are now in areas of dense vegetation, and might still exist, or might not.
Wow. How many deeds have you had to reconcile with different calls from different directions with different distances. I'm in the hundreds, if not thousands.
That is what surveyors do.
The likely hood of all monuments being destroyed is slim to none. There is always something to hang your hat on, thus you can duplicate those footsteps. Hang your hat and you'll sleep better than WGS 84.
a subdivision plat that i have been lately perusing states "BENCH MARK BASE ON U.S.GS. MEAN SEA LEVEL". no other BM or vertical info is on the plat.
i've been thinking of asking the surveyor to see his level loop from the gulf and back. i think he has a 1-foot bust in there at about Corsicana. ;^)
This statement appears on numerous surveys from the same person. A quick check shows he is usually on or near grid or localized to an existing map. His explanation is that he used GPS so all of his bearings are geodetic. Gentle attempts at education have proven futile. Pointing out the legal requirement to use and declare a line between 2 monuments did no good either...
I wonder if he did an inverse calculation between two grid points to get that geodetic bearing?
Bill
a MN firm but an IA seal
> This statement appears on numerous surveys from the same person. A quick check shows he is usually on or near grid or localized to an existing map. His explanation is that he used GPS so all of his bearings are geodetic. Gentle attempts at education have proven futile.
Yeah, that's a problem
> Pointing out the legal requirement to use and declare a line between 2 monuments did no good either...
Texas used to have that requirement. It always bugged me though. If my bearings are related to Geodetic (or grid, which is still based on geodetic at some defined meridian) then my "line" is a longitudinal line. There are no monuments (unless the candy stripe poles really do exist at the North and South poles - however that wouldn't really help since every line between the two candy striped poles will be North or South).
The plan control works fine using a state plane configuration for control validation. I have no issue reproducing the state plane coordinate system. I do have an issue reproducing NAD83 vertical datum.
What am I missing? What is wrong with the opening threads datum? Yes the vertical could have some adjustments since 1983 but the horizontal seems adequate to me.
The only likely choices for vertical are NAVD88, NGVD29, and a city datum. There isn't a NAD or an 83 among vertical datums.
