The state has experienced the common problem of a mismatch between the regulatory requirements and the data available to meet those requirements. The state elevation data obtained from USGS quad sheets can be as much as 50 years old and is of medium resolution (30 meters). GIS analysts often use these data in combination with high-resolution satellite imagery to create GIS products such as orthorectified products. However, merging older digital elevation models from the USGS quad sheets with high-resolution imagery can degrade the accuracy of the final data product, reducing the value of the remote sensing data.

North Carolina is subject to periodic hurricane damage that causes severe physical damage to the state and often has economic repercussions. Though many places on the East Coast suffered from Hurricane Floyd in 1999, in North Carolina Floyd was preceded by Hurricane Dennis and followed by Hurricane Irene, a combination that exacerbated the damage to property caused by Hurricane Floyd. The immediate damages in the state from Floyd were 51 deaths and a cost estimated to be $3.5 billion,⁶ but the hurricane had longer-term impacts as well. For instance, many people moved out of North Carolina because of the flooding and the physical damage, a loss in population that created fiscal problems in later years.

In assessing the impact of the hurricane, it became clear that changes in terrain due to development and even flood damage in recent years meant that the state’s flood insurance rate maps were badly out of date and that residents of North Carolina had often been using outdated and inaccurate information to insure their homes and property. In response to this situation, and to protect its residents and the state in future years, North Carolina decided to establish a flood mapping program to obtain, process, and disseminate accurate, current, and detailed data on elevation and flood hazards over the entire state and to provide these data in both digital and hard-copy formats. The state has committed itself to creating by 2006 digital terrain maps covering 48,700 square miles with a vertical accuracy of 20-25 centimeters.⁷ Under its commitment to create the new digital flood insurance rate maps (DFIRM), North Carolina has contracted with two firms that will obtain lidar data using airborne sensors. Initial mapping is determined by river basins rather than counties because flooding is a function of