Topographical mapping in littoral regions using the GPS backpack tideline tracing skill

Abstract

Inter‐tidal zone survey methods are varied and have progressed with the advancement of survey technology. The most significant features of a method are its restrictions on the topography to which it can be applied and the efficiency of the transition from fieldwork to processing or mapping of the dataset. This paper provides details of a GPS backpack method, indicates it is well matched with the altitude measurements obtained by the real‐time kinematical positioning technique, and contrasts it to the use of echo‐sounders when the littoral zone is submerged. A comparison of the results obtained by the tideline tracing method, varying by at least 20 cm, indicates that echo‐sounder measurements were less accurate with poorer resolution, and more laborious in mapping the topography of the littoral region. In the inter‐tidal zones inside Taichung Harbour and off the Pali coast, where gentle beaches have wide, flat low tide terraces crossed by a series of longshore bars and runnels, the tideline tracing method successfully provided topographical data on the centimetre scale. This method sampled denser data points distributed on the local slope, such as the slopes off the berm and the terrace in Taichung Harbour being all clearly defined with the gradients around 3–7°.