The yellow dots are visual confirmation of a deal with real geostrategic significance. These are Philippine fishing boats, plying their trade in the rich waters around Scarborough Shoal in the South China Sea, their presence here implying an agreement was 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.

Here's another image, courtesy of Planet Labs, of the same shoal on the following day: the Chinese coastguard is still inside the lagoon but the fishing boats have moved slightly further south.

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 coast guard vessel, guarding the mouth of the lagoon and preventing Philippine 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 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.

“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.”

So was it new arrangement 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 shows as red dots (with one boat still guarding the mouth of the lagoon) and Chinese fishing boats as orange. There are no Philippine boats: China had been aggressively chasing them away.

Relations between the two countries nosedived after China seized control of the shoal in 2012, and Manila took Beijing to an international court of arbitration in The Hague. That court ruled that China's vast claims to the South China Sea had no legal, historical basis and complained, among other things, that Beijing was unfairly denying Philippine fishing boats access to Scarborough Shoal.

China's immediate response was to go on the offensive. A series of images on the AMTI website taken through September show a complete absence of any Philippine boats around the shoal, which lies around 120 nautical miles off the coast of the Philippines' main island of Luzon.

But rewind a little further back, and the picture becomes less clear. This image, from May, shows Philippine boats fishing around the shoal without any sign of a problem. Chinese coast guard boats would sometimes chase them away before the arbitration ruling, but not always.

Rather than any dramatic new deal, it seems that China has just returned to the status quo that was in effect for most of the Benigno Aquino III presidency, prior to the July ruling, said Gregory Poling, the director of AMTI.

“That effectively meant a permanent China Coast Guard presence in the lagoon, which prevented any Filipino access inside the reef, and regular Chinese patrols farther out that sometimes allowed Philippine fishermen to work the outside of the shoal and sometimes chased them off,” he wrote in an email.

On his return from Beijing, Duterte suggested a deal had been reached that fishermen from neither country would be allowed to fish inside the lagoon for environmental reasons — it is a spawning area for tuna and other fish. But that environmental concern has come rather late in the day, Poling argues.

“On the environmental issue, I suspect Duterte is looking for a way to sell continued inability to access the lagoon without conceding the reality of Chinese control,” he wrote. “We haven’t seen any Chinese fishermen inside the lagoon in a while, but they did massive damage in 2014 and 2015, especially digging endangered clams.”

So how big a win was this for Duterte?

Experts are skeptical, said Heydarian, especially because China seemed to have tightened its grip on the shoal in recent months.

“The images of jolly fishermen taking home their catch has helped ease tensions and strengthen Duterte's diplomatic capital,” he wrote in an email. “But this is easily reversible if China cuts off access to the lagoon area again.”

Online comments from ordinary Filipinos to the news from Scarborough Shoal have not been uniformly positive, with some people angry that China should be granting a “concession” to the Philippines over a reef they believe is rightfully theirs.

Given Duterte's volatility and unpredictability, and China's dogged pursuit of its maritime claims, the risk of further upsets in the relationship cannot be ruled out.

And as an editorial in the Philippine Star pointed out, an even more thorny issue still lies between the two nations in the form of Mischief Reef, known in the Philippines as Panganiban, which is also controlled by China.

The tribunal ruled that Mischief Reef lies within the Philippines' continental shelf and Exclusive Economic Zone, and criticized China's land reclamation and building program there as creating a “fait accompli.”

“President Duterte has said the ruling is non-negotiable even as he strengthens Philippine ties with Beijing. His resolve will be tested in Panganiban,” the editorial said. “One of his Cabinet members had remarked that Chinese aid comes with no conditionalities or strings attached. At this point in fact it does, and the conditionality is worse than adherence to the Universal Declaration of Human Rights: giving up the Philippines’ sovereign rights in contested waters.”