DAVID-II: A Globally Reconstructible, Singularity-Free Coordinate System with Quantified Error Bounds

This archive contains the reference Python implementation of DAVID-II, a globally defined, reversible spatial coordinate representation system developed to address the reconstruction limitations of the original DAVID framework. DAVID-II encodes geographic position using a deterministic coordinate quadruple(n,Ai,uΩ,ψ)(n, A_i, u_\Omega, \psi)(n,Ai,uΩ,ψ), where spatial location is represented relative to quantized radial shells, a fixed set of deterministic anchors, a normalized angular separation, and an anchor-local azimuth. This extension resolves the intrinsic underdetermination of shell-based coordinate systems and enables full encode–decode reconstruction with quantified error bounds. The implementation uses standard WGS84 geodesy, includes forward and inverse transformations, and is accompanied by a comprehensive test suite covering named locations, polar and dateline edge cases, random global sampling, and performance benchmarks. All reported errors are measured directly and reflect known sources such as shell quantization, anchor spacing, and floating-point precision. This software is provided as a research reference implementation intended for reproducibility and technical evaluation. It is not proposed as a navigation system, safety-critical tool, or replacement for existing geodetic standards or GNSS infrastructure. No claims regarding physical ontology or empirical instantiation are made. Access is restricted pending further development and domain-specific evaluation.