We overlay upon the Earth a grid of rectangular pixels. Every Pixel has a size of 0.72 km2 (0.278 sq. mi.). Pixels are classified according to a 2-tier system:
- Tier 1: Areas with high population density
- Tier 2: Rest of the world
The classification is based on worldwide population density data made available by the European Commission under its Global Human Settlement Layer.
Tier 1 pixels are those where the population density is estimated at 2,000 inhabitants per square kilometer or more.
The reward pool for outdoor sensors (Type 1 and 2) is further split across pixel tiers (70% for Tier 1 and 30% for Tier 2).