Where's North Korea's Kim? Lets see what the satellites say.

It is the North Korean version of Kremlinology adapted for the modern age - with images taken from orbit a key part of trying to monitor Pyongyang's missiles, nuclear sites and more. Now, the views from commercial satellites offer potential clues as the world tries to figure out Kim Jong Un's whereabouts.

New satellite images of luxury boats owned by the North Korean leader have been spotted at his villa in the coastal resort of Wonsan, providing more evidence that Kim is probably holed up by the beach, according to NK Pro, a specialist news and analysis service based in Seoul. 

The revelation comes days after satellite photos also showed what is probably Kim's personal train parked at a railway platform reserved for his use near the villa in Wonsan, according to researchers at 38 North, a website affiliated with the Stimson Center.

As rumors swirl about Kim's health, they provide some of the best evidence yet that reports of Kim's demise might be premature. But they certainly do not show whether he is fit and well.

North Korea watchers still pore over the phrasing of state media reports and the placement of officials at important events for clues about what is in Kim's mind, for hints of ideological debates and power struggles, for clues about who is up and who is down among his entourage - and sometimes even for signs of who might have been executed or imprisoned.

The satellite-image scrutiny usually goes for bigger targets such as military activity. But the current analysis into Kim's personal world reinforces how much North Korea remains a puzzle to the world despite Kim's groundbreaking outreach to South Korea and the United States, including two summits with President Donald Trump.

But the experts at NK Pro, 38 North and other specialist groups now have access to regular eyes in the sky from commercial services Planet and Maxar, as well as less frequent historical images from Google Earth.

Images come in every day and are scoured for clues about North Korea's nuclear and missile programs: a trailer being parked here, steam coming from a facility there, scaffolding or a platform being put up somewhere else. 

But they are also being used to look for planes, motorcades, trains and boats.

It's like a giant game of "Where's Waldo," with an entire country to scour but few key clues.

"In a country like North Korea, there's no noise when it comes to luxury facilities," said Colin Zwirko at NK Pro. "It's only Kim family facilities. There's no other people that could be just freely enjoying boat parties or having mansions in remote places."

When reports emerged that Kim might have had a cardiovascular operation at a hospital near Mount Myohyang on April 12, experts looked for confirmation from the skies.

Kim's grandfather, Kim Il Sung, reportedly died at a mansion on the top of the mountain in 1994, although that mansion was demolished in 2012. There are still some villas in the area, but no obvious signs in satellite photos of unusual activity, said Zwirko.

There was also talk that Kim might have attended a missile test near Wonsan on April 14. The complex at Wonsan on North Korea's east coast has a private beach, guest villas, a horserace track and a basketball court, and it is believed to one of Kim's favorite places to stay.

First, 38 North spotted that Kim's train had arrived at Wonsan sometime between April 15 and April 21. It was still present on April 23, "when it appeared to be repositioned for departure," 38 North reported. 

On Tuesday, Zwirko announced that he had spotted an approximately 60-meter (200-foot) leisure boat positioned for use in the villa's private harbor, as well as two other large leisure boats used by Kim in the area. The main boat was seen in a photograph when Dennis Rodman visited Kim and went to Wonsan in 2013, and it is believed to have a pool on board under a roof.

But Zwirko also did what he called a baseline survey, cross-checking years of satellite imagery against state media reports and NK Pro's own database.

He has spotted Kim's train at Wonsan on eight occasions since 2013. On seven, he was able to confirm that Kim was staying at Wonsan or attending an event in the area.

Similarly, he has listed 23 occasions since 2013 when the boats were taken out of storage and placed ready for use. On 14 of those occasions, he was able to confirm that Kim had been in the area.

In other words, he said, the boat appears to be brought out of storage for Kim to use. Along with the train, the images indicate that the leader is likely to be staying at Wonsan, an assessment backed by senior South Korean officials with access to intelligence reports.

That does not mean that Kim is in perfect health, although a flurry of official letters in his name suggests to many observers that he is at least alive and conscious. 

The alternative, of course, is that North Korea is playing an elaborate trick to buy time - issuing statements, moving boats and trains around - to fool the outside world.

"What I can conclude from my research is that there has been a high correlation of these boat activities in Wonsan when Kim is around," said Zwirko. "And I would expect this to be no different unless the theory of purposefully moving boats around to trick us is true. I have confidence that the pattern should hold - the boat movement activities indicate a high chance he's in the area."

Chad O'Carroll, who founded NK Pro, said commercial satellite images are really helping with investigations of contemporary issues in North Korea in ways that simply were not possible when Kim's father and predecessor, Kim Jong Il, died in 2011. 

"What people have been able to do recently with the train out at Wonsan and now the boats, it's really impressive and probably worries the North Koreans somewhat because this technology is only going to keep improving," he said. "And by another 10 years from now, just imagine what we'll be able to see - it should be pretty mind-blowing."