Do you know where you are right now? You probably have a rough idea, and if you want a better one, GPS is there for you. The GPS chip in your phone measures how long it takes to receive simultaneous signals from the four nearest GPS satellites. Taking account of these time-lapses, your phone knows how far it is from each satellite. And from this, it can tell where it is in the world—a value it then translates into the familiar language of latitude and longitude, which your phone’s map program displays via an iconographic blue dot. This is how GPS verifies your location.

Sometimes we give others access to this GPS-derived location. If an NFL sportscast is unavailable to mobile devices in a certain area, the TV provider wants proof that you and your mobile device are not within it. This transmitted information is extremely easy to fake. With some inexpensive tools, the same technology that proves your location can be exploited to bear false witness for everyone else.

The rate of fakery will likely increase in the coming years—as will incentives to stop it. “If a company is hooked into a permission-less system, and says that anyone who comes to a certain store can win credits, and it’ll all happen on the blockchain, GPS spoofing becomes a huge problem, because now anyone can strain your reward system,” says Ryan John King, cofounder and CEO of FOAM, a Brooklyn-based startup. “For anything that’s autonomous or decentralized and requires location proof, people will just lie about their GPS location and get their reward.”

King’s background is in urban planning and architecture. FOAM’s origins are in Foamspace, an art project organized by King, along with collaborators Ekaterina Zavyalova, Nikolay Marynov, and Betty Fan. The exhibit, which won a 2015 New York Street Architecture Prize award, consisted of large cubes of geofoam (lightweight polystyrene often used as a fill material in large infrastructure projects) piled near the street fronting the museum’s building in Lower Manhattan. Anyone who could prove they were physically located at the spot were sent “community-building tokens.” The Foamspace group later built a “tropical mining station”—a pneumatic space whose walls were inflated by the heat and excess energy generated from mining Ether—for the Chicago Architecture Biennial.

The projects were meant to provoke discussions around the possible uses of blockchain, and the implications of decentralization, among the architecture community. They also served as an object lesson for the creators. “We realized there is no protocol for interacting with space on the blockchain,” King says.

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FOAM wants to establish a location verification method that would eliminate the need for GPS and its open-to-fakery weakness. People with special radio beacons establish themselves as “location authorities,” staking their claims with tokens and forming networks similar to the ad hoc “things networks” around the world that handle IOT applications. The beacons then exchange messages to synchronize their clocks, a method currently used by “indoor GPS” systems in places like underground mines, where GPS signals can’t penetrate. If something requiring verification enters a zone bounced by four beacons, the beacons gauge its location by measuring the time it takes for the four signals to reach it. The beacons then store this information on a local blockchain, and then reach a consensus regarding the object’s location. After verifiers have checked the information against data recorded in other zones, the information is printed to Ethereum’s blockchain. The requester receives the verification via a decentralized app.

The first stage of the system would handle only static objects, but FOAM is also developing a system of verifying the location of dynamic objects. It hopes continuously to verify the location of dynamic objects moving through a zone, including taxis and ride-share vehicles.

“I think the proof-of-location stuff that FOAM is doing sounds pretty cool,” says Randy Meech, co-founder and CEO of StreetCred, another company experimenting with blockchain and open-source mapping. “We’d definitely want to use something like that.”

Around the same time last month, StreetCred and FOAM debuted similar version of a “consensus map,” another idea floating around the geospatial blockchain community. The idea is to have groups of self-interested people compile a communal map of “points of interest” (POI)—a term for anything on a map that occupies a set point, as opposed to something linear (like a road) or spread-out over a wide area (like a county). StreetCred’s MapNYC contest, held through October 2018, is an attempt to build a POI map of New York City. Anyone who downloads a mobile app can place a POI on the map, along with some basic information, including the correct classification (bar, restaurant, park, church, and so on). Other users attest to the accuracy of the POI or flag it for incorrect information. Once enough users have verified the accuracy of the POI, the creator and the verifiers receive credits.

StreetCred has set aside a prize pool of eight bitcoins for the top 100 scorers. The winner will receive one bitcoin, and the rest will be split among the next 99. (Full disclosure: I’ve been participating in MapNYC and I’m currently on-track to win .02 BTC, or around $122.) The prize explains why anyone would want to participate, and also why StreetCred would want to use location-verification. The company has had to banish some users from the contest who were spoofing their location to log spots across the city en masse. (This is a problem that has long plagued location-based games like Pokemon Go.) What it doesn’t explain is why StreetCred would pay for a consensus-driven POI map. Hasn’t that been done? Isn’t there one on my phone right now?

The answer is yes, there is. But it’s a proprietary map owned by Google. “It’s the hardest data set to amass,” Meech says of POIs. “Google has amazing data, but they don’t share it with anyone.” Companies that need the data to operate—such as Uber and Tesla—license it from other companies. Meech is willing to bet that these companies would welcome an open-source POI map, and that they will support a blockchain project to make it happen. Meech imagines a map economy driven by businesses who would inject crypto in the system, incentivizing data gatherers who know they can earn crypto by doing their job. Maps would develop organically, with companies making the largest crypto investments in areas poorly mapped presently.

Meech has been involved in open-source mapping projects for a decade, including a stint as CEO of Mapzen, an open-source platform that shut down earlier this year. “What caused me to get bitten by the crypto/blockchain bug is that we were shutting down services that 70,000 developers were using,” he says. “The idea of building something that could outlive the company is what really brought me to it.”

MapNYC is a very preliminary attempt to build this kind of system. The only blockchain element is the bitcoin award. FOAM’s project is larger—a consensus-driven POI map of the world—but it also more exclusive. For now, participation is limited to the approximately 1000 people who responded to FOAM’s token sale last summer. Placing a POI on the FOAM map requires a stake of tokens. Anyone who wants to challenge the accuracy of an entry must also stake tokens, with the larger community weighing in to settle the dispute. Depending on which way their consensus goes, either the creator or the challenger walks away with the tickets.

For FOAM, the economic impetus for creating POIs is more vaguely defined, involving a kind of tokenized equity stake that would increase with one’s participation. “One critique I’ve heard, which I guess StreetCred solves, is ‘what are my incentives?’” King says. “Of course, you’ll get a lot of people if you’re giving out $50,000, but once that money’s gone, where do you go next? They’re saying the company could sponsor a contest, but there will always be someone fronting the money. FOAM is a curation market, where the token is used to curate the list. There’s skin in the game, because you have to deposit tokens.”

“We have some philosophical differences. From being in the map industry for awhile, I think the data-sets they collect will be limited to people who really understand crypto. And that means you’ll be missing a lot of things,” says Meech, talking of FOAM. “It can’t be just crypto people or open-source people—we’ve seen that happen in the past, and it doesn’t work. It needs to be suburban moms adding the doctor’s office.”

As the contest winds down, it’s difficult to gauge the success of MapNYC’s attempt to map the city’s five boroughs. The emerging POI map shows a plethora of points in Manhattan, Brooklyn and Queens (Williamsburg, Prospect Heights, Park Slope, Cobble Hill, Prospect Lefferts Gardens, Astoria, Long Island City). These places are full of young techies one would expect to take an interest in such a contest. The Bronx has a smattering of points, but Staten Island, despite StreetCred’s promise of bonus credits for points logged there, remains mostly POI-less. Altogether, MapNYC has produced about 20,000 POIs—less than the 25,000 StreetCred was aiming for, but not a bad start for a consensus-driven map of a very large city.

“It’s a way to test some of our assumptions,” Meech says. “It’s not a perfect test of what people would do for crypto incentives, but it gets software into the hands of people. Hopefully, we’ll have the best data-set in New York when this is over. We’re swinging for the fences a little bit.”