Cuarteron Reef (Huayang Jiao 华阳礁 in Chinese; Calderon Reef in Filipino; đá Châu Viên in Vietnamese) is a reef at the east end of the London Reefs in the Spratly Islands of the South China Sea. It is controlled by China as part of Sansha, and claimed by the Philippines as part of Kalayaan, Palawan. The reef is 3 nautical miles long and has an area of 8 square kilometres.
On 12 July 2016, the tribunal of the Permanent Court of Arbitration concluded that Cuarteron Reef contains, within the meaning of Article 121(1) of the Convention, naturally formed areas of land, surrounded by water, which are above water at high tide. However, for purposes of Article 121(3) of the Convention, the high-tide features at Cuarteron Reef is rocks that cannot sustain human habitation or economic life of their own and accordingly shall be entitled to 12nm of territorial sea measured from its baseline but have no exclusive economic zone or continental shelf. 
Chinese construction projects
Carteron reef has a supply platform and a reef fortress. In 2015 the Philippine government release what it claimed were photos of a six-story facility being built by the Chinese government on the reef. Also in 2015, China completed the construction of a 50 metre high lighthouse on the reef. By late 2015, China had expanded the reef's usable area to 0.23 square kilometres (0.089 sq mi), reportedly including in the process two helicopter pads, and possibly gun, radar and missile emplacements. As of 2016, China was reportedly building a high-power radar installation on the reef.
- D. J. Hancox; John Robert Victor Prescott (1995). A Geographical Description of the Spratly Islands and an Account of Hydrographic Surveys Amongst Those Islands. IBRU. pp. 14–. ISBN 978-1-897643-18-1.
- "Award" (PDF). Permanent Court of Arbitration. 12 July 2016. p.259
- "China expands construction work on reefs in dispute with the Philippines". The Asahi Shimbum. Retrieved 23 February 2016.
- Lin, Ting-Hui. "China’s Lighthouses in the Spratlys". The Diplomat. Retrieved 23 February 2016.
- "South China Sea: China completes construction of lighthouses on artificial island on Cuarteron Reef". Australian Broadcasting Corporation. Retrieved 22 February 2016.
- "China ups the ante with lighthouses in S China Sea". Today. Retrieved 23 February 2016.
- "Cuarteron reef tracker". Center for Strategic and International Studies. Archived from the original on 2016-03-04. Retrieved 2016-03-05.
- Page, Jeremy; Lubold, Gordon. "U.S. Bomber Flies Over Waters Claimed by China". The Wall Street Journal. Retrieved 23 February 2016.
- Denyer, Simon (22 February 2016). "Satellite images show China may be building powerful radar on disputed islands". The Washington Post. Retrieved 22 February 2016.
- "China’s New Spratly Island Defenses". Center for Strategic and International Studies. 2016-12-13. Retrieved 2016-12-17.
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