Hi All,
I'm interested to hear of any developments/guidance from agencies (fed or local) for GPS protocol/standards when submitting wetland delineations using map-grade GPS receivers. In particular, if the map-grade GPS can be verified to have 1-meter horizontal accuracy in area of usage, an agency will accept the delineations, and a surveyor will sign off? Or, is sub-meter required for jurisdictional acceptance?

Some counties in Florida are taking the lead w/regard to setting protocol and guidance on this matter.

Tom,

I can only speak for the projects that I have been involved with but we have always used a Trimble TSC-1 GPS unit which claims sub-meter accuracy, although I question it at times. As far as protocol from regulatory agencies I have not seen any or been questioned or asked to provide a survey rather than GPS. Hope this helps.

Dave

Dave,

Sounds like you are probably getting submeter horizontal with that Trimble, and glad to hear that the agencies aren't requiring survey submittal and accepting your GPS outputs. Helpful info.

Thanks, I'll add to the post as this issue progresses here.

Tom

I have not seen guidance on using GPS for wetland mapping. I have had regulators tell me that 5’ +/- GPS mapping would not be good enough for a permit application (inaccurate impact calculations), but have never been questioned on the mapping accuracy when there was clearly no impact to the wetland. It comes down to accuracy if impact/lack of impact.

I will note that surveyors often use GPS receivers to map wetlands and topography and certify the survey.

I was forwarded this link by DEQ today concerning GPS requirements in VA. This is my first exposure to this guidance and I will add that I have yet to be required to provide any documentation except the simplest of descriptions of the GPS unit itself. Hope this helps.

http://www.nao.usace.army.mil/redesign/technical%20serv...nce/GPS_guidance.pdf

The USACOE Galveston District has a policy on GPS and delineating wetlands that maybe useful/helpful.

www.swg.usace.army.mil

I know that the GPS requirements vary from Corps District to Corps District.

In the NAD, there are some Districts which accept DGPS use as long as there is verifiable accuracy below sub-meter. However, there are other Districts which require verification that the equiment is accurate to 15 cm or less.

GPS becomes quite a contentious issue as nobody really can get their hands around it from a HQ point of view.

Mike in Charm City