There are actually even more. You can actually have 12 different variations depending on certain choices. Though the other sources of differences are minor. ht

There are actually even more. You can actually have 12 different variations depending on certain choices. Though the other sources of differences are minor. https://arxiv.org/abs/1711.02508 https://arxiv.org/abs/1711.02508 This is actually a great source of frustration in the robotics state estimation community, as you have the influential University of Minnesota using JPL, and most other universities using Hamiltonian.