In the context - a hackathon sponsored by the US Department of Defense - it has great utility. GPS (and any radio-based location system) is quite vulnerable to denial by enemy jamming. This technique would by extremely relevant in a war between peers, and probably provides a much lower cost option than high-precision inertial navigation systems.

Tangentially, this isn't really new - ground-pointed RADAR system combined with a good terrain dataset can also be used.