The **Esri Projection Engine Database Documentation** repo provides the full, version‑controlled data set that the Esri Projection Engine (PE) library uses to look up coordinate reference systems, datums, ellipsoids, units, transformations, etc. It supplies the factory database in multiple formats (JSON, CSV, text, shapefile, file‑geodatabase, and objedit) together with guidance on how to add custom entries, and is intended for GIS developers and GIS professionals who need to understand, extend, or integrate the PE coordinate‑system definitions into ArcGIS or other spatial software.