I'm reading your paper "acoustic inertial underwater navigation". Is it convenient for me to know the implementation details?

[1ADZX]

Hello, I'm reading your paper < acoustic inertial Underwater Navigation >, and I'm interested in section a linear triangulation in Chapter 4. I'd like to know how you get the initial relative pose (R, P) between sonar frame I and sonar frame N in your article?

Is it through the essential matrix of polar geometry between sonar frames? Thank you in advance