Abstract: The topography of tidal flat has the characteristics of rapid change. In the tidal flat area covered by salt marsh vegetation, acquiring topography data by terrestrial laser scanning (TLS) is affected by surface salt marsh. In order to study the precision of TLS on topography of salt marsh covered area and the relationship between its accuracy and vegetation coverage, we took the Phragmites australis, Imperata cylindrica, and Spartina alterniflora communities and Scirpus mariqueter as the research objects. The vegetation filter algorithm,based on the moving window method supplemented by cluster analysis, was used to recover the terrain and topography features from point cloud data. The results showed that:1) the higher the vegetation coverage,the lower the accuracy of TLS topography retrieval was, a negative correlation; 2) the penetration of TLS was different with the type of vegetation:when the vegetation coverage was greater than 50%, the original coverage that laser could not penetrate was 70%, 65% and 65% of Imperata cylindrica, Spartina alterniflora,and Scirpus mariqueter communities respectively, and the root-mean-square error (RMSE) was 22.0, 22.0 and 8.6 cm, respectively; when coverage equaled to 50%, RMSE of topography retrieval was 16.0 cm of Imperata cylindrica community, 6.6 cm of Scirpus mariqueter community, 4.5 and 5.7 cm respectively of Phragmites australis and Spartina alterniflora communities; when coverage was less than 50%, with the decrease of the coverage, the accuracy of topography retrieval of the Phragmites australis, Spartina alterniflora and Scirpus mariqueter communities increased slightly, while that of the Imperata cylindrica community was improved more obviously. 3) When using TLS recover topography in the salt marsh area, the higher and the more of the TLS setting direction in the same area, the better the accuracy of the topography retrieval was.

Key words: salt marsh vegetation, terrestrial laser scanning, vegetation filtration, topography, Yangtze River estuary coast