Recently, the Beijing Surveying and Mapping Design & Research Institute received a commission from the Beijing Municipal Bureau of Cultural Heritage to find the old site of Longxugou and to restore the Tianqiao site at the intersection of the central axis and Longxugou. Tianqiao, or the “Heavenly Bridge”, is the southernmost bridge located on Beijing’s central axis, which is a heritage project of great historical significance and cultural value.

After receiving the task, the Beijing Surveying and Mapping Design & Research Institute immediately organized personnel to prepare the data and find the historical information related to the Longxugou. Division one of the Institute is responsible for the completion of the project. After a half day of information searching, they found that Longxugou was not only the drainage for rainwater but also domestic sewages. In 1929, Longxugou was transformed into an underground drainage with its bottom built by bluestone slabs, walls by masonry and the top by granite slabs.

By accessing information and integrating the topographic map and all the drainage information near the Tianqiao intersection, on the morning of June 18, the head of Division One, Gao Chao and the orange team member, Wu Jie led the whole team and carried out the field work of finding the Longxugou.

During the field work, they used the underground pipeline photogrammetry instruments to check and verify various types of large drainage ditches near the Tianqiao intersection one by one, and obtained the image data of the bottom of the well. After comparing and analyzing with historical data and through field visits, they finally obtained the exact location of the intersection of the old site of Longxugou and the central axis.

The timely and efficient completion of this project within such a short time has fully demonstrated the emergency response ability and excellent proficiency of the surveying and mapping crew. Relevant crews all felt a strong sense of accomplishment for being able to make contributions to the application of the Beijing Central Axis as a world cultural heritage site.