The areas to be surveyed, and hence the structures to be surveyed were defined by the Heinz Center.
The field survey data was obtained by the following method:
An advance team sent to the study area established local elevation control points using geodetic surveying procedures. A reference GPS station was established at an NGS control point and a second roving GPS unit was sent out with a field crew to establish local elevation control points in the areas where the surveyors were to survey structures. The GPS receivers were operated in real-time kinetic mode when establishing these local elevation control points.
The structure survey crew was typically a three man crew consisting of a level operator, a rod man, and a GPS operator. Using a local elevation control point as a reference point, the survey crew proceeded through the neighborhood to be surveyed, using conventional level techniques to establish the reference elevations for each surveyed structure. In many cases access to each house was sufficient and allowed the reference elevation to be determined with high accuracy. In other cases, access to the property was not possible or denied by the owner. In those cases, the rod man could not be used so other methods to establish the reference elevation for the structure were utilized. These alternate methods included, but were not limited to, establishing the height of doorknobs and porches from which the reference elevation could be estimated based on common building practice. While the leveling was going on, a GPS operator with a real time differentially corrected (from beacon receiver) code GPS receiver established a position in the street, then established a bearing and range offset to the approximate center of the structure. These bearing and offset corrections were applied to the field data before GIS processing in the case 3001, Inc. produced data, but during the course of GIS processing for Towill, Inc. supplied data. An electronic data logger was used by all crews to record the structure characteristics.
The structure characteristics of house number, house subnumber, street, city, structure condition, Elevation Certificate building type, number of floors, foundation type, reference elevation, elevation of lowest grade adjacent to the structure, breakaway walls (presence), basement (presence), swimming pool (presence), the structure purpose and a picture of the structure were all obtained by field survey. All other attributes on the structures arise from GIS operations with the other data layers.
The Federal Emergency Management Agency (FEMA) is conducting a national 'Evaluation of Erosion Hazards' study that will determine whether erosion hazard areas should be mapped and whether flood insurance risk classifications should be established to more directly reflect the effects of long-term erosion on the premium rates of the NFIP. In the conduct of this study, FEMA has mapped erosion hazard areas for 27 counties distributed among 18 coastal and Great Lakes states. The erosion hazard mapping was done in conjunction with the Coastal Zone Management agency for each participating state. The erosion hazard maps are to be used strictly for the conduct of the 'Evaluation of Erosion Hazards' study, and have no regulatory purpose or authority.
These data are one in a set used for this 'Evaluation of Erosion Hazards' study.
All items that describe the intermediate 10 year positions of zone values (p*0_zone, p*0_bfe, p*0_intbfe) are derived by moving the structure ocean-ward along its transect. For example, the projected zone of a structure in year 30 (p30_zone) is determined by moving the structure 30 years toward the ocean and finding it's position in the current zone. In 60 years the structure will move ocean-ward a distance equivalent to the difference between the Current ERF and Projected ERF along the transect (eha_width). Therefore, at each 10 year increment the structure moves a distance of (year/60) * (eha_width) along its transect.
These data have been developed from the best available sources. Although efforts have been made to ensure that the data are accurate and reliable, errors and variable conditions originating from physical sources used to develop the data may be reflected in the data supplied. Users must be aware of these conditions and bear responsibility for the appropriate use of the information with respect to possible errors, scale, resolution, rectification, positional accuracy, development methodology, time period, environmental and climatic conditions and other circumstances specific to these data. The user is responsible for understanding the accuracy limitations of the data provided herein. The burden for determining fitness for use lies entirely with the user. The user should refer to the accompanying metadata notes for a description of the data and data development procedures.
Although these data have been processed successfully on computers at FEMA, no guarantee, expressed or implied, is made by FEMA regarding the use of these data on any other system, nor does the act of distribution constitute or imply any such warranty. Distribution of these data is intended for information purposes and should not be considered authoritative for navigational, engineering, flood hazard, flood insurance, legal and other site-specific uses.