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| Beach Survey Team | Sample Profile |
The LIDAR airborne laser beach mapping data set featured on this CD-ROM is currently being evaluated for its utility for mapping elevations and shoreline change on South Carolina beaches. LIDAR data provided on this CD-ROM are derived from an aircraft remote sensing technique used to gather coastal topographic measurements. This technique provides coastal resource managers the opportunity to gather regional and high spatial resolution coverage of beach elevations with high vertical and horizontal accuracy. Using LIDAR data to collect shoreline topography is proving to be faster and less costly than traditional beach surveying methods. Many coastal states can benefit from this technology, as shoreline measurements are needed to determine erosion rates, setback lines, and sand volume needs for beach nourishment projects. Shoreline change measurements can also help coastal resource managers estimate the effects of jetties, groins, seawalls, and the effectiveness of beach nourishment projects. For more information about LIDAR data, click here.
The South Carolina Department of Health and Environmental Control (SCDHEC) Office of Ocean and Coastal Resource Management (OCRM), is the regulatory agency that has monitored South Carolina's beaches since 1988. Field teams are deployed twice a year, in the
spring and fall, to conduct beach surveys. There are over 400 monuments
along South Carolina's coast at which these teams take measurements.
There are many different participants in the project, including local
colleges and universities, private consultants, and SCDHEC OCRM staff.
Upon completion of processing the data, a document, "The Annual
State of the Beaches Report", is generated. This report includes
beach profiles at the monuments and also notes general topographic change.
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| Beach Survey Team | Sample Profile |
Using traditional beach survey methods, data are collected in a transect seaward from a benchmark. Conversely, remotely sensed LIDAR data provide a more cost effective, efficient means of collecting topographic information, provided that subtidal data are not needed. Furthermore, the data set collected is extremely dense, accounting for topographic changes along the entire beach rather than just along transect lines. SCDHEC OCRM is considering using the LIDAR data as a means of generating baseline data. Currently, testing is being conducted to determine the accuracy of this new method of collecting topographic data relative to traditional survey methods.
One method of viewing remotely sensed LIDAR data in a geographic information system (GIS) is a grid. Grids are geographic data models representing information as an array of equally sized square cells. Each grid cell has a value that corresponds to the feature or characteristic at that site, such as a soil type, vegetation class, or in this case, elevation. Values of the cell can be stored in a database file that is connected to its geographic x, y location.
Grid data sets of the 24 islands and beaches on South Carolina's shore are large, requiring a substantial amount of hard drive storage space. Additionally, the user must have GIS software, such as ArcView® Spatial Analyst®- a separate ArcView extension, that can analyze grid data. Contours, which have smaller file sizes than grids, are another option for viewing LIDAR elevation data.
Unlike grids, contours show only the outline of the elevations generated from the LIDAR data. Using contours alone, the features of the beachfront cannot be easily detected. To alleviate this problem, over 90 aerial photographs of the natural dune line were scanned and georeferenced. Using ArcView, the contours could be overlaid on the aerial photographs.
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Contours generated from the 1997 LIDAR data set were evaluated using the following steps. First, regions along the natural dune line were extracted. Next, the density of the data set was reduced by gridding or clipping the data. Finally, contours, at 1-foot vertical intervals, were created. To aid identification of beach features and landmarks, the contours were overlayed onto aerial photographs.
Using a Global Positioning System (GPS) receiver, which uses satellites to record the latitude and longitude position of the receiver, SCDHEC OCRM staff walked along the crests of the primary dunes. SCDHEC OCRM uses the location of the primary dune crest to determine the distance behind the dune line where new development can take place. The GPS locations were converted to a digital file and incorporated into a GIS. The image below displays the GPS data overlaid on a LIDAR grid.
The data generated from the GPS receiver and the LIDAR data match up extremely well for Edisto Island, as displayed in the image above. At the time of publication, SCDHEC OCRM was processing and evaluating the data for the other 23 islands and beaches along the South Carolina coast. For more information about SCDHEC OCRM, click here.
The following links provide information about LIDAR data and multiple ways for viewing the data.
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