01 // SPHERICAL PROJECTION S2 FACE UNROLLING & MAP TANGENT FACE 1 P(lat,lng) POINT P: [37.7749°, -122.4194°] FACE PROJ: FACE 1 (UV MAP) FACE UNROLL 02 // HILBERT QUADNODE SUBDIVISION RECURSIVE SPACE-FILLING CURVE (LEVEL 3) Q0 [00] Q1 [01] Q2 [10] Q3 [11] CELL: L3-N38 (30KM²) HILBERT POS: 38 / 63 BIT ENCODE 03 // 64-BIT INTEGER CELL ID COMPACT COMPOSITE KEY & BIT MAP BIT 0 BIT 3 BIT 9 BIT 63 FACE ID 001 [3 BITS] HILBERT PATH 10 01 10 [LEVELS 1-3] SENTINEL 1 [BIT 9] PAD ZEROS 00...00 [54 BITS] UINT64: 5573423719489536000 HEX ID: 0x4D5A000000000000 SPATIAL INDEX LOOKUP