Airborne LiDAR has certainly improved the accuracy of flood mapping, but the work is far from complete. In a way this is good news for the service providers, but the challenge is in finding the funds to pay for the projects, and determining accurate elevations.
The NGS – The National Geodetic Service, the US Geological Survey and the Federal Emergency Management Agency – FEMA, along with a host of smaller agencies all collaborate to produce accurate flood maps.
GPS is used with the airborne LiDAR sensors to determine the 3D coordinates of each LiDAR point. Determining the latitude and longitude is a straightforward process, but as reported recently in Government Computer News translating the height obtained from the GPS into sea level referenced elevation requires knowledge of the gravity model for the area being mapped. This is still a major challenge in many parts of the country.