Elevation and Flood Planes

How are Elevations Established?

Elevation information is established by the National Geodetic Survey (NGS), a federal agency within the National Oceanic and Atmospheric Administration. The NGS is responsible for the installation of benchmarks that meet specific reliability requirements for stability and survey accuracy. Professional Surveyors and Mappers understand how to obtain the recorded elevation information for these benchmarks and use this elevation information to identify existing elevations of buildings and ground.


There are two elevation datums available for use in Collier County. The older datum is the National Geodetic Vertical Datum of 1929 (NGVD). NGVD is no longer supported for use by federal agencies, but older documents that use NGVD are generally still valid and the elevations can be converted from NGVD and NAVD. Professional Surveyors and Mappers understand how to make the conversion.

The newer and current elevation datum is the North American Vertical Datum of 1988 (NAVD). The flood elevation information on the Digital Flood Insurance Rate Map (DFIRM) is based upon the NAVD. All new elevation certificates are required to use the NAVD as the elevation datum.

Elevation Certificates

The elevation certificate is an important administrative tool of the National Flood Insurance Program (NFIP). It is used to provide elevation information necessary to ensure compliance with the NFIP, Florida Building Code, and the County’s flood damage prevention ordinance, to determine the proper insurance premium rate, and to support a request for a Letter of Map Change (LOMC).

The elevation certificate is required in order to properly rate Post-FIRM buildings, which are buildings constructed after publication of the Flood Insurance Rate Map (FIRM), located in flood insurance Zones VE, AE, AH, and A. Since passage of the Flood Insurance Reform Act in 2012, certain conditions may require the preparation of an elevation certificate for Pre-FIRM buildings. [Note: For Collier County and Marco Island a building is considered Pre-FIRM if the date of the building permit is prior to September 4, 1979. For the City of Naples the Pre-FIRM date is July 2, 1971.] An elevation certificate can also be used if the building is being rated under the optional Post-FIRM flood insurance rules.

As part of the agreement for making flood insurance available in a community, the NFIP requires the community to adopt floodplain management regulations that specify minimum requirements for reducing flood losses. One such requirement is for the community to obtain the elevation of the lowest floor (including basement) of all new and substantially improved buildings, and maintain a record of such information. The elevation certificate provides a way for a community to document compliance with the community’s floodplain management ordinance.

Use of the elevation certificate does not provide a waiver of the flood insurance purchase requirement. Only a LOMC from the Federal Emergency Management Agency (FEMA) can amend the FIRM and remove the Federal mandate for a lending institution to require the purchase of flood insurance. However, the lending institution has the option of requiring flood insurance even if a LOMC has been issued by FEMA. The elevation certificate is used only to certify building elevations. A separate floodproofing certificate is required for floodproofing of non-residential buildings.

Surveyor Information

If you are going to purchase flood insurance or desire to remove your home from the Federal flood insurance purchase requirement, an elevation certificate will need to be prepared. Check the County’s Elevation Certificate Map to see if an elevation certificate is on file.  A Professional Surveyor and Mapper must establish the elevation information of the structure.  Here is a list of Professional Surveyors and Mappers, which is updated quarterly.