Abstract: The binary image method can automate extraction of tidal datum referenced shorelines from light detection and ranging (LiDAR) data. With this method, spatially detailed and continuous shorelines can be derived. In this paper, an improved binary image method is developed in order to promote efficiency. Firstly, data preprocess is applied to the LiDAR data, including coordinate transformation and noise reduction, with the exception that no filter is used to generate an LiDAR DEM. Secondly, the LiDAR data is segmented into a binary image by intersection with the MHWS (mean high water springs) datum surface, whose height calculated by the tide gauge data or tidal model. Thirdly, the tidal datum referenced shorelines from the LiDAR data are extracted by a chain of image processing procedures, including object recognition, bogus-objects deletion, and edge detection. Finally, the accuracy of shorelines is evaluated by the comparison of LiDAR-derived shorelines with the ground survey data. An application shows that the improved method is more efficient and more reliably than the binary image method.