Fellow New Lab Member FOAM implemented their first Zone for Proof of Location in the Brooklyn Navy Yard this year, and its powered by Voltaic solar panels and IoT battery packs.
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FOAM builds tools to enable a crowdsourced map and decentralized location services. FOAM Location is a network of radios that offers secure location services independent of GPS. The radios are LoRa and can cover a large area with minimal power consumption. You can dig into the details on their site and especially in their whitepaper.
For FOAM, the Brooklyn Navy Yard provided a dense urban environment to test their system and will be an ongoing testing site. They have four rooftop nodes at different altitudes and spaced up to 500m apart.