This is because each of these features may generate different zones of influence around them.

"The whole debate is about who has control and sovereignty over these maritime features, and thus the zones around these features that would give exclusive control over the seabed, subsoil and water column."

The designation of a landmass determines precisely how the surrounding water can be used and who can use it.

For example, an island is granted a territorial sea area of 12 nautical miles (22.2 kilometers) and a continental shelf of 200 nautical miles, and these can be used to claim an exclusive economic zone of 200 nautical miles. These factors have implications regarding access to natural resources in the water and on the seabed, Tzanakopoulos said.

In contrast, a rock is granted a territorial sea area of 12 nautical miles, but no exclusive economic zone. A low-tide elevation is not granted a territorial sea area, but it may be used as a base point in claiming territorial waters if it is within 12 nautical miles of land.

"Any determination by the tribunal that a particular maritime feature is a low-tide elevation, for example, would preclude any claim to sovereignty over that feature, as it is incapable of appropriation," the academic said.

The Philippines claims that an area extending 200 nautical miles from its coast, except for 12 nautical miles of high-tide land, is its exclusive economic zone and continental shelf. Manila has accused Beijing of interfering in its exercise of sovereignty and jurisdiction in its territorial waters.

The Philippines also argues that China's claim to historical rights within the nine-dash-lines in the South China Sea violates its sovereignty and jurisdiction over non-biological resources on the seabed.

Tzanakopoulos said he believes the tribunal made a mistake in accepting that it has jurisdiction over some of the Philippines' claims. "If it responds to the Philippines' claims, in some sense it is prejudicing issues that are not within its jurisdiction," he said.

Chinese officials and experts have defended China's stance of nonacceptance and nonparticipation in the case, saying the Philippines' unilateral initiation of the arbitration violates international law.

The tribunal's decision is expected soon.

cecily.liu@mail.chinadailyuk.com