These are the available options that allow a vehicle to estimate its position without a GPS. Once enabled this allows all autonomous and semi-autonomous modes just as they do would a GPS is available.
- MarvelMind Beacons
- Optical Flow
- OptiTrack motion capture system
- Pozyx Beacons
- ROS cartographer
- Visual Odometry with OpenKai and ZED
The low cost IMUs (accelerometers, gyros, compass) used in most flight controllers drift too quickly to allow position estimation without an external velocity or position source. In other words, low-cost IMUs on their own are not sufficient for estimating position