Instead of using one conservative error bound for all satellites, the method assigns differentiated bounds across elevation intervals, allowing protection levels to better track real positioning errors. In offshore and open-ocean tests, the approach improved system availability while still suppressing misleading information, pointing to a more reliable navigation framework for safety-critical offshore operations. Modern marine engineering, offshore resource development, and vessel positioning increasingly depend on real-time precise point positioning (RT-PPP) because it can deliver high-precision positioning without a local base station. But precision alone is not enough: maritime users also need integrity, meaning the system must warn them when positioning cannot be trusted.…