Military low-level air maneuver in contested environments is constrained by adversary radar surveillance and the need to minimize exposure while remaining terrain- and mission-feasible. Although terrain masking reduces direct line-of-sight (LOS) to a radar, detectability cannot be assessed from geometry alone, as it also depends on the radar energy budget, receiver noise, processing gain, and the adopted detection criterion. This paper presents a reproducible GIS-oriented workflow that couples LOS-based masking products, including visibility and minimal visible altitude above ground level (AGL), with an energy-based detectability model expressed through signal-to-noise ratio (SNR) and probability of detection (PD). The workflow further incorporates scenario-dependent atmospheric modifiers representing gaseous attenuation, rain attenuation, and refractivity-driven propagation effects, while retaining the possibility of higher-fidelity propagation modelling where required. In addition to 2D exposure layers, the approach supports constrained low-exposure route generation and optional 3D voxel-based representations of detectability in the near-ground layer. A case study in the Brno area demonstrates the generation of LOS and altitude-margin products, SNR/PD raster layers, and example low-exposure corridors derived from raster threat masks. The results show that radar exposure is highly sensitive to terrain, altitude, and environmental assumptions, and that the proposed workflow provides a transferable decision-support framework for comparative analysis of low-level operations in contested airspace.