Facebook doesn't only know what its 2 billion users "Like."

It now knows where millions of humans live, everywhere on Earth, to within 15 feet.

The company has created a data map of the human population by combining government census numbers with information it's obtained from space satellites, according to Janna Lewis, Facebook's head of strategic innovation partnerships and sourcing. A Facebook representative later told CNBC that this map currently covers 23 countries, up from 20 countries mentioned in this blog post from February 2016.

The mapping technology, which Facebook says it developed itself, can pinpoint any man-made structures in any country on Earth to a resolution of five meters.

Facebook is using the data to understand the precise distribution of humans around the planet.

That will help the company determine what types of internet service — based either on land, in the air or in space — it can use to reach consumers who now have no (or very low quality) internet connections.

"Satellites are exciting for us. Our data showed the best way to connect cities is an internet in the sky," Lewis told about 150 people gathered in San Francisco this week for a Space Technology and Investment Forum sponsored by the Space Foundation.

"We're trying to connect people from the stratosphere and from space," using high-altitude drone aircraft and satellites, to supplement Earth-based networks, said Lewis.

Facebook hired Lewis, a former intellectual property lawyer with extensive experience in international aerospace law, about one year ago.

Her job, as she told the forum, is to work with partners in the aerospace industry to build a multi-pronged network to serve the entire planet.

The data is used "to know the population distribution" of Earth to figure out "the best connectivity technologies" in different locales, Lewis said. "We see these as a viable option for serving these populations" that are "unconnected or under-connected," she said.

In addition to Lewis, Facebook is also hiring aerospace engineers to help it crack this market.

The mapping technology is part of a much broader effort by U.S. companies to take advantage of a slew of data now available from the hundreds of satellites orbiting the earth.

"All this satellite data is coming from space, so people are trying to figure out what the business opportunities are," says Edward Swallow, senior vice president for civil and commercial systems for the Aerospace Corporation, an entity set up by the government in 1960 to protect America's pre-eminence in space.

Facebook rival Google, for example, sold its satellite-imaging business, formerly called Skybox, earlier this year "because they figured out they could get the data without having its own satellites," Swallow told CNBC in an interview.