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Survey BenchmarksPublic Works

City of Santa Barbara

Survey Benchmarks

2008 Height Modernization

Overview:
Between May 2007 and June 2008, the City of Santa Barbara Survey Crew performed a “Height Modernization Leveling Project” to upgrade the City’s Survey Benchmarks, from the superseded National Geodetic Vertical Datum of 1929 (NGVD 29) to the North American Vertical Datum of 1988 (NAVD 88), which is the datum used on the City’s digital map. The survey specification followed Second Order Class I procedures. For this project, all level loop closures met First Order tolerances, except one loop, which met Second Order Class I tolerances.

Hereafter, these are the only benchmarks the City will maintain and publish. Click on the “Benchmark Map” link for benchmark locations and ID names. Click on the “Benchmark Listing” link for Benchmark ID names, elevations, and descriptions.

Accuracy:
The relative accuracy for the conventionally leveled heights is expected to be better than 0.01 feet. Combining the leveled elevations of SBCN points with GPS measurements provides the means to utilize GPS as a replacement tool for conventional leveling, and to establish NAVD 88 elevations within the City at the level of about one centimeter (0.03 feet).

Application:
This survey provides a basis for using GPS technology as a replacement tool for conventional leveling to establish NAVD 88 elevations. The results of this project can be applied in several ways to obtain elevations using GPS assuming the user understands the methods, procedures, and site requirements to obtain accurate ellipsoid height differences between points. Click on the “2008 Height Modernization GPS Survey Report” link to read more about proper procedures.

Links:

Last Updated: Aug 26, 2014