Introduction

The National Geodetic Survey (NGS) has determined that it was necessary to readjust the national vertical control network. The current reference is in the National Geodetic Vertical Datum of 1929 (NGVD 29). The vast majority of products of the Federal Emergency Management Agency, National Flood Insurance Program (NFIIP), which is administered by the Federal Insurance Administration (FIA), are currently referenced to NGVD 29 for vertical control data (ground, structure, and flood elevations). To remain in compliance with the national standard, FIA will be converting its products to the new national datum, as mandated by Congress the North American Vertical Datum of 1988 (NAVD 88). This conversion will necessarily take place in a gradual process driven by the opportunity to republish our Flood Insurance Studies (FISs) and Flood Insurance Rate Maps ( FIRMs ) for other substantive reasons. In following with these changes Hillsborough County has entered into the CTP Agreement with FEMA. This is an avenue for FEMA to recognize the County's active role regarding flood mitigation, which provides the potential to receive Federal monies in the future. The CTP Agreement is an initial step in building a partnership with FEMA, whereby both parties recognize the fundamental importance of flood hazard identification, flood insurance, and floodplain management. As a partner with FEMA, the County will be in a better position to accomplish a variety of projects that will lead to the update of County Flood Insurance Rate Maps.

National Geodetic Survey NAVD 88 Publications

Background of Vertical Reference Datums FAQs