This conversion calculator is provided as a convenience to facilitate access. Flood Elevations of effective FIRMS are referenced to the vertical datum NAVD 88. Many cities and counties such as Hillsborough County are upgrading to the NAVD 88 standard as well. Unambiguous vertical datums in the coastal environment are critical to the. Tools such as those found on the NOAA National Geodetic Survey and the Office of Coast Survey websites can be used to convert elevation values between datums. Johns River water management districts also have migrated to NAVD 88. The National Geodetic Survey (NGS) provides a vertical datum conversion tool known as. Agencies Using NAVD 88Īll federal agencies, including the Federal Emergency Management Agency, are required to use NAVD 88.

The datum change, which involved a surveyed recalibration of active District water-level data collection sites to the NAVD 88 standard, has been completed. Process and TimelineĪll historic and future water level data is published in both datum standards (NAVD 88 and NGVD 29) and made available through the District’s Water Management Information System (WMIS). Gauges that read in the NAVD 88 standard are labeled with a sign indicating the elevation datum.įor the exact measured shift of a specific District data collection site, email In addition, the National Geodetic Survey (NGS) has created a tool to help people estimate the “shift” between the two datums for a specific latitude and longitude. Thus, the transformation between two levelling-construct vertical datums necessitate in having common benchmarks in the two systems while the transformation.

Vertical datum conversion