1. What is local mean sea level?
2. What is the National Geodetic Vertical Datum of 1929 (NGVD 29 )?
3. Why is a change of the datum necessary?
4. How does the North American Vertical Datum of 1988 ( NAVD 88 ) do this?
5. When will the change to NAVD 88 take place?
6. Can the current datum continue to be used?
7. Datum which should be used in completing FEMA elevation and flood proofing certifications?

8. Does this change affect all NFIP communities?
9. Will local community vertical control networks be required to be re-leveled?
10. Have the U. S. Geological Survey ( USGS ) and the Corps of Engineers ( COE ) bench marks been revised?
11. What are the differences between NAVD 88 and NGVD 29?
12. Where can the new NAVD 88 bench marks be found?
13. What are some of the potential problems of mixing datums?
14. Will the datum change result in new BFE's or flood depths?

Local mean sea level (LMSL ) is the result of hourly values of still water levels that are observed over a period of 19 years. LMSL can be used for a vertical datum of reference that is based on the observation of one or more nearby tidal gaging stations.