The atoll measures 5.7 km along its longer southwest-northeast axis, and is up to 3.5 km wide. Its total area including the lagoon and rim of the reef measures 16 km², and the lagoon is up to 22 meters deep.
The reef is occupied and controlled by China (PRC) and claimed by Taiwan (ROC), the Philippines, and Vietnam. In July 2012, a large fleet of 30 Chinese fishing vessels arrived at the reef from Hainan.
In April 2015, a Philippine Navy aircraft patrolling near the reef received "aggressive action" from a Chinese ship. Also in 2015, the USS Lassen sailed within 12 nautical miles of the reef, prompting the Chinese Foreign Ministry to call the action a "provocation" and they vowed to keep building up in the South China Sea. As per the US Navy, this was a routine "freedom of navigation" exercise. Similar exercises are performed routinely about 12-28 times per year.
In September 2015, reports and photographs appeared that indicated China was developing the reef into a military base, comparable to their one at Fiery Cross Reef.
In November 2015, two U.S. B-52 strategic bombers flew in airspace near the area. They were contacted by Chinese ground control, but were allowed to continue their mission undeterred.
^http://news.qq.com/a/20120725/000453.htm Chinese language page with a collection of 10 photos of the reef and Thitu (Pagasa) Island dated 25 July 2012. Pictures 1,3,4&6 show the buildings on the reef; 5 shows a lighthouse, 7-10 show Pagasa.