Open MVP & Zone Expansions

Further progress has been made on the FOAM Proof of Location MVP! Our recent update post shared a demo of the MVP process for proving location onchain using on our mobile app and a prototype user device. Today, the FOAM team is excited to share additional features that have been added to our MVP, as well as exciting updates on the plug-and-play radio (”Zone Anchor”) and user device (”Mobile Node”).

A reminder that the FOAM MVP is a full-stack minimal version of Proof of Location onchain. The output of Proof of Location is a “Presence Claim”, an NFT representing a user’s location and time. The purpose of these Presence Claims is to serve as a new primitive for innovative crypto and non-crypto applications alike to reference secure geospatial data. Verifiable location data is a highly scare resource in the digital world today and is especially important for anything onchain, as blockchain apps inherently expect and require verifiability to allow people to transact online without trust.

This post highlights the latest features added before the MVP launch!

New Hardware

Over the past few months a major focus has been finishing and testing the new plug-and-play Zone Anchor called Gyroid, and designing a new version of the mobile node meant for sale called Cycloid. The plug-and-play Zone Anchors are now fully integrated with our software stack and have been deployed for testing in existing Trust Zones.

We have seen extremely encouraging initial test results, that show much larger coverage areas with this advanced hardware than with the older Raspberry Pi Zone Anchors. For example, in dense urban areas lacking line of sight, like Williamsburg and Dumbo Brooklyn, we are able to get Presence Claims from Zone Anchors 3km away. This would presumably be much larger in suburban areas or urban areas of less density like most other cities.

Gyroid Zone Anchors deployed in Williamsburg, Brooklyn NY
Gyroid Zone Anchors deployed in Williamsburg, Brooklyn NY

The new mobile node Cycloid (product version), we designed it to be pocket-sized with a small screen and no need for connection to internet, except for the initial setup. It also has RF amplifiers to boost the signal for more coverage. We will be sharing the designs soon, so stay posted for further updates on both Gyroid and Cycloid.


Past posts have spoken to the importance of allowing users to produce varying degrees of location data onchain. FOAM can provide Presence Claims of the highest quality that require all Zone Anchors in the Zone being involved in the localization, or it can provide less-secure but more plentiful Presence Claims, like in areas of less coverage. This opens a trade-off space for users or developers building on FOAM to choose between having more location data (i.e. more coverage), or more secure and accurate data. A classic trade-off between quantity and quality.

Zone Anchors Light Up when receiving signed transmissions from a user: A Witness
Zone Anchors Light Up when receiving signed transmissions from a user: A Witness

FOAM now allows users to mint a type of Presence Claim referred to as a “Witness”. A Witness is not a localization per-say (i.e. calculated with TDoA), but rather a record of a cryptographic handshake between a Zone Anchor and a user (”mobile node”).

Where previous demos focused on full localizations, Witnesses are able to be minted with the least amount of coverage, like if only one Zone Anchor in the Zone hears the mobile node as a weaker form of Proof of Location.

These witnesses show as Purple in Hostel, our mobile app as compared to higher tiers of localization. The Mobile user flow below shows only 2 Zone Anchors hearing the user, so only a Witness can be minted:


As more of a technical upgrade to the MVP smart contracts and Hostel backend, a bounty system was implemented for Presence Claim payments. This means that when someone requests a Presence Claim, they put up a “bounty” saying they want a Presence Claim and are willing to pay x $FOAM for it. This is similar to an intent/solver-based architecture, in which users indicate what they want, and Hostel fulfills the request.

For the MVP, this is abstracted away in the Hostel user-flow. Although, it is an important security feature for the long-term because it addresses an architectural vulnerability that would exist otherwise, wherein someone could effectively DDOS the system by requesting Presence Claims, requiring Hostel localizers to do work to localize them and generate Presence Claims, but then the user not actually mint the PCs to compensate Hostel for the work.

Presence Claim NFT Images

Now, when users mint Presence Claims, a unique image is generated for the Presence Claim NFT. The image is based on the geohash and quality of the Presence Claim. The circle around the FOAM logo in the image indicates the quality, determined by how many Zone Anchors in the Zone were involved in the transaction. Currently there are three types of Presence Claim NFT images: 1. Witness, described above 2. Localization 3. Filtered Localization (more accurate)

The colors of the FOAM logo inside the circle are determined by the geohash. Geohashes are hashes that encode geographic coordinates. Each Presence Claim has a geohash representing the user’s location at the time of creation.

A Presence Claim NFT with corresponding image
A Presence Claim NFT with corresponding image

Leaderboards & King of the Hill

Hostel now provides a set of leaderboards measuring participation and activity in the FOAM Proof of Location MVP. There is a user leaderboard showing which users minted the most Presence Claims, a Zone leaderboard showing which Zones generated the most Presence Claims, and a King of the Hill leaderboard showing the last user to mint a Presence Claim in each Zone and the time since mint. If you are the last person to check in at a Zone, you are the King of the Hill, and its your objective to hold this title as long as you can 🚩

Different Leaderboards shown in the Hostel mobile PWA
Different Leaderboards shown in the Hostel mobile PWA

FOAM Proof of Location is still gated to Trust Zone Program participants with Zones so activity is limited, but this will change soon once the MVP is launched onchain for anyone to use! Note: leaderboard activity is currently wiped whenever we redeploy our devnet chain and contracts are reset every other week.

xFurther build outs gamifying aspects of Proof of Location are under development to introduce geospatial gaming as one of many novel use cases only made available by Proof of Location.

Look out for our post early next week on upcoming FOAM events for Consensus in Austin Texas.

Next Steps:

Our core objective these next couple of months is to open the Proof of Location MVP for anyone to use. We are working diligently on this, and will have more to share as we get closer to making it public. This goes hand-in-hand with deploying more Zones with the plug-and-play Zone Anchos so there is more coverage for people to interact with. We have immediate plans to deploy new Zones in Manhattan, Austin, San Diego, Rockaway Beach, Jersey City and more. We will also be finishing the new mobile nodes and opening a pre-order for people interested in getting their own for use with the MVP. Stay tuned for further updates on all of this!

Finally, as a reminder, $FOAM now has a Velodrome pool on OP Mainnet where you can trade FOAM for low fees or pool liquidity for high APRs. Check it out if you have not yet!

FOAM is a Proof of Location technology for applications needing secure location services. It enables a handshake between the location service providers and the user, proving the user’s location. Terrestrial radios and time-of-flight algorithms are used to perform localizations, and digital signatures ensure the location data cannot be spoofed. The system is completely independent of satellite-based location services like GPS.

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