GNSS-denied navigation is a long-standing challenge. Navigation with inertial measurement units (IMU) suffers from position drift. A Doppler lidar can measure its own velocity directly, relative to local terrain. This is not possible with "conventional" pulsed lidars. Velocity data can be used to significantly reduce drift.
The lidar measures velocity along multiple directions to get the full vector. This is similar to navigation of autonomous underwater vehicles, where acoustic 'lidar' also known as Doppler Velocity Logger is used. NASA uses this technique for planetary landing. Compact Beamlet lidar makes this navigation method feasible for small aerial and ground robots. Moreover, it provides additional functional benefits.
Doppler lidar (400 ft range)
9-axis IMU + barometer + GNSS
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