California Surveyors Forums

Well, the usual story. The County's benchmarks are on the NGVD 29 datum and I need NAVD 88.
NGS is publishing NAVD elevations only to the nearest foot.

Does Caltrans have anything to the nearest tenth along Highway 29?
How is VERTCON working out in the Napa Valley?

Please advise.

I would submit a request for any control
from cal-trans they have a form you fill out
indemnifying them but they have been responsive to me.

I don't know the contact in your area so be prepared to
sit on the phone for a while going thru voice mail.

Brian

Vertcon is a good check but I do not trust it, depends on what you need.

http://www.dot.ca.gov/hq/row/landsurvey ... ntacts.pdf

This is in District 4.

The NGS is not maintaining passive monuments any longer. If you look at the datasheets, many have not been visited since 1991. There may be many issues with a brass disk; subsidence, tectonic movement, disturbance, etc.

The simplest solution is to upload your GPS dataset to OPUS. Get a precise solution. Otherwise, a RTN solution will work for some projects.

The FEMA Elevation certificate actually states that you can use RTN solution (identify the provider) or an OPUS solution.

"For the benchmark utilized, provide the PID or other unique identifier assigned by the maintainer of the benchmark. For GPS survey, indicate the benchmark used for the base station, the Continuously Operating Reference Stations (CORS) sites used for an On-line Positioning User Service (OPUS) solution (also attach the OPUS report), or the name of the Real Time Network used."

Turns out the City of Calistoga commissioned a survey a couple years ago to provide horizontal and vertical control monuments within City limits.

Sweet, I guess you have had a few earthquakes
in the area talking with friends in Lakeport.