POSITION_STEP_AU

Position quantization step.

Positions are stored as signed 32-bit counts of this. At 1 AU per step the representable range is ±2.1 × 10^9 AU ≈ ±34,000 ly, comfortably past the 150 ly the file covers, and the quantization error is bounded by half a step. That sounds enormous until you compare it to what it is quantizing: at 150 ly the parallax uncertainty on a HYG position is several thousand AU, so the quantizer is four orders of magnitude inside the measurement error and is, for practical purposes, free.

universe/src/catalog/format.ts:58