Evaluation of Sub-aerial Topographic Surveying Techniques Using Total Station and RTK-GPS for Applications in Macrotidal Sand Beach Environment

Accurate documentation of monitoring beach topographic changes is an essential component of coastal process research and management. Thanks to rapid development of technology, accuracy and quality of recent beach land surveying data have improved accordingly. As increasing demand for detailed beach topography, the adoption of a proper survey design and data collection strategy is also a crucial factor in order to collect high-density data accurately and efficiently within a given time. Especially, an efficient topographic surveying technique, by which the required time and manpower for a survey can be minimized, should be considered in the case of macro-tidal beach environment having a limited daytime for surveying the exposed intertidal zone. As a part of the Coastal Erosion Monitoring And Prediction (CEMAP) system development program of the Korea Institute of Ocean Science and Technology (KIOST), we conducted accuracy and efficiency tests for four different beach-profile surveying methods of: 1) spot measurement using a total station; 2) spot measurement using a RTK-GPS system; 3) continuous walking measurement using a RTK-GPS backpack system; and 4) continuous measurement using a RTK-GPS system mounted on an all-terrain vehicle (RTK-GPS ATV system) at the Gosapo macro-tidal sand beach, South Korea. Test results indicate that the RTK-GPS spot measurement method have the lowest vertical error of about 2 cm, which includes equipment and operation errors, while the rest of them have similar vertical errors with a range of 3 - 6 cm. In terms of survey efficiency, the RTK-GPS ATV system have advantages in surveying time and operational manpower with a reasonable vertical error of about 3 cm over the other surveying methods. As a result, The RTK-GPS ATV system is the most suitable surveying method for examining the beach volume and morphologic changes in a macrotidal sand beach, while the spot measurement methods using the total station or the RTK-GPS system are adequate for accurate beach-profile change analysis.