Coastal ecological restoration engineering elevation transformation method analysis

Ecological restoration project is an important project in the coast area. To perform strict construction and acceptance surveys, high-precision normal elevation data need to be quickly obtained for the construction area. GNSS technology can quickly acquire geodetic height data, but the method for converting it to normal elevation is regionally specific. Therefore, based on GNSS geodetic height data measured in Haikou's west coast, this article compares and analyzes three different elevation conversion methods (direct method, GNSS leveling method, and indirect method) and applies them to the construction progress analysis of ecological restoration projects. The results indicate that there is approximately a 1.2-meter deviation between the geodetic level model derived from the EGM2008 gravity field model and the local leveling control point datum in the Haikou west coast area, so the direct method using EGM2008 cannot be used for elevation conversions in this region. The indirect method overcomes the pure mathematical fitting of the GNSS leveling method and absorbs the local features of the geodetic leveling model in this region. Using the results of the indirect method, key indicators such as beach shoulder elevation, seaside boundary, and the amount of sand fill can be calculated, which can be applied to the construction verification of coastal ecological restoration projects.