Got a call from a longtime client.
The GIS guy in some department at world headquarters wanted all the data we have been sending them from now on in NAD 27.
We have been working with them since 1998 and everything we have done has been in NAD 83. Quit using 27 yeeeears ago unless it's some sort of legacy project and those are always a pain.
Tried to talk them out of it by telling them it's an old system and not very accurate and that the proper way to get the coordinates is to locate the actual monuments and it would be best to rent a helicopter and tie into the old monuments (it's a fairly remote location and most of the old control points are not something you can drive to), or we could just use one of the conversion programs and do a guesstamation of the coordinates-of course that was the option they want.
Oh well; guess we just have to charge them for the extra work.
My guess is that it's oil & gas, and all of the base maps and seismic data was generated in 27, thereby making around here about 100' difference between datums.
We get the same request. We still survey in 83, but provide 27 and 83 coords on the well plats.
It happens. I just did all this with one of my bigger clients. I actually made a base map for them in 27 just to make it all jee and haw correctly.
Don't fight battles that don't need fighting. Keep doing what you're doing and send the finals in 27.
All of the offshore lease blocks in the Gulf of Mexico are still leased on the NAD27 collection of coordinate systems, including UTM expressed in U.S. Survey Feet. Since all positioning offshore is now performed with GPS, the BLM once published the rule that all datum transformations MUST be done using NADCON.
Other considerations to think about nowadays can be found at the Amercas Petroleum Survey Group's website. http://www.apsg.info/
Yeah, I'm just having a little rant.
Spending time with something silly can get painful.
What I think happened is this:
The company hired a GIS guy and he when out and started to locate facilities.
The old GIS guy who went to another company had a good handle on all the databases and had set up a pretty detailed GIS system.
The new guy was finding "errors" in the locations and must have set up a new database using the GCDB (which by the way is up to 1500' off in some places here, usually it's within 100') and his locations. Well his findings were that facilities weren't where they are supposed to be so I stupidly said, "He's not locating using 27 is he?"
So here we are. A brand new dataase shifted about 170' to NAD27 has been created.
Some of the regulators no longer allow NAD27 and one of the states we work in has a law that no legal location will be allowed to be expressed in NAD27 after 1993 (although no one seems to be aware of that code in the mapping industry) so I thought we had expunged it.
What the company wants to do is give both 83 and 27 so I'll set up a new 27 database and export my data back and forth.
Thanks for the link Cliff; I'll put that on my favorites and take some time to look through it some good stuff on it.
We also have quite a bit of older projects that still need to be done using 27 data because they started in the 70's, 80's and early 90's. But those all have established control tied into the monumented 27 system. Trying to shift between 83 and 27 with NADCON usually ends up causing a 1-6 foot (6' is unusual) error on those projects. Not bad really if you think about how 27 was surveyed.
So what we do on those projects is to "calibrate" to existing control-with mixed results-and hope enough control is still available.
The BLM here has dropped 27 from their acceptable data sets which I thought might be the end of it.
