The yellow dots are visual confirmation of a deal with real geostrategic significance. These are Filipino fishing boats, plying their trade in the rich waters around Scarborough Shoal in the South China Sea, their presence here proof of an agreement reached during President Rodrigo Duterte's recent visit to Beijing.

On that visit, Duterte announced his “separation” from the United States and his embrace of China: something that would amount to a significant strategic realignment for a key regional American ally.

In return, he won a pledge of Chinese investment to upgrade his country's infrastructure. He also, it seems, won permission for fishermen to return to these rich waters, around a shoal that China seized in 2012.

Philippine President Duterte in China: 'America has lost'

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Philippine President Duterte in China: 'America has lost'(Reuters)

Yet there are reasons to question the limits of the concession that Duterte gained.

The first is the single red dot on the satellite image. It's a Chinese coastguard vessel, guarding the mouth of the lagoon and prevent Filipino fishing boats from entering, according to the Asia Maritime Transparency Initiative at the Center for Strategic and International Studies.

China's claim of sovereignty over the shoal, which it knows as Huangyan Dao, has not been relaxed, as Foreign Ministry spokeswoman Hua Chunying underlined on Monday.

“The Chinese side has always been exercising normal jurisdiction over Huangyan Dao. The situation there is and will remain unchanged,” she told a regular news conference on Monday.

“We have seen all-round improvement of China-Philippines relations following President Duterte's visit to China,” she added. “Under such circumstances, the Chinese side makes proper arrangements based on the friendship between China and the Philippines in response to the issue of President Duterte's concern.”

But how big a concession has Duterte really won from Beijing?

Was it a “one time symbolic breakthrough” or part of a longer-term provisional modus vivendi in the area? asked Richard Heydarian, an expert in politics and international affairs at Manila's De La Salle University. Will China continue to take a relaxed view of fishing in the area or will it one day cut access again?

This image, from September 2016, is typical of the period before Duterte's visit. Again, the Chinese coast guard show as red dots, (with one boat still guarding the mouth of the lagoon) and Chinese fishing boats as orange. There are no Filipino boats: China had been aggressively chasing them away.