In a permissionless network, anyone can claim to be running a node anywhere. Without a verification mechanism, rational actors would fake locations, simulate coverage, and collect rewards without deploying any hardware. This is the Sybil problem applied to physical infrastructure — and solving it is what separates serious dePIN protocols from token farming schemes.

Helium's Proof of Coverage uses encrypted radio-frequency challenges between hotspots. A Challenger node sends a beacon; nearby Witness nodes attest reception; the Challengee hotspot proves it heard and responded. Because radio signals obey physics, a fake hotspot at a fake location cannot realistically respond to challenges from real hotspots. The system isn't perfect, but gaming it requires real hardware at real locations.

GEODNET takes a different approach: its RTK base stations broadcast GPS correction signals. The network verifies contribution by checking whether the correction data is accurate and timely against known reference positions. You cannot fake centimetre-precision GPS data — either the signal is real and correct, or it isn't.

WeatherXM's weather stations submit meteorological readings that the network cross-validates against neighbouring stations and satellite data. Implausible outliers are discarded; consistent, physically plausible readings are rewarded. This creates a self-correcting data quality mechanism without requiring trusted oracles.