Height Modernization and GNSS Real Time Network Program

About the Program

Category: Information Technology (Best in Category)

Year: 2012

The FEMA Digital Flood Insurance Rate Maps (DFIRM’s) for Mohave County that became effective in November, 2009 are mapped in the new North American Vertical Datum (NAVD) of 1988. In 2008, the vertical datum used in Mohave County was the older National Geodetic Vertical Datum (NGVD) from 1929. In order to assist our local professionals in submitting data and surveys that relate to the new FEMA mapping in the correct vertical datum, the Mohave County Flood Control District funded the NAVD-88 Height Modernization Project which established a primary network of 57 NAVD-88 survey control points approved by the National Geodetic Survey (NGS) throughout the 13,400 square mile area of Mohave County. Once the primary network was established, the task of developing a secondary network of reliable benchmarks in the county's populated areas was addressed by partnering with National Geodetic Survey (NGS) and the State of Arizona to develop a Real-Time Network (RTN). Time savings with a four person GPS crew including vehicles were $10000/week. Dramatic efficiency improvements when compared to total station surveys. The Mohave County RTN eliminates the need to establish supplemental traverses for construction staking and topographic surveys. Overall, this program was a great money and time saving success for the county. The Real-Time Network is a seven base-station GNSS (Global Navigation Satellite System) project. The system provides local communities with a surveying solution with 1-5 centimeter accuracy in the new NAVD88 vertical datum of the latest FEMA Digital Flood Insurance Rate Maps (DFIRMs) and it provides many additional benefits as well.