Detecting the remaining structure foundation using ground penetrating radar: The outer wall of small east gate of Taiwan-FU, Taiwan

This study investigates the underground remaining foundation of the outer wall of the small east gate of Taiwan-FU at Tainan, Taiwan using the ground penetrating radar (GPR). The gate and the outer wall were torn down between 1912 and 1913. Before the geophysical detections, limited literature and photos in the 18th- and 19th-century referred the outer wall of the small east gate. In this study, the GPR detections along with the in-situ archaeological excavation give the location and the size of the outer wall. The investigations show that size of the outer wall of the small east gate is larger than the existing outer wall of the main south gate of the Taiwan-FU city. Therefore, the "small" east gate had a notable military use to protect the Taiwan-FU city during the 18th- to the 19th-century. In addition, GPR is a useful tool to identify the location and the depth of underground foundations before a new underground structure passes underneath the structure.