Change from biasAccOmegaInt to biasAccOmegaInit

[varunagrawal]

Made these changes a few years ago, and wanted to create the PR for whenever it was deemed appropriate to merge.

This PR changes all instances of biasAccOmegaInt to biasAccOmegaInit which is the correct name for the initial noise on the bias for both the accelerometer and the gyroscope.

[ProfFan]

Wanted to do this for years, but I'll let Frank decide :P

[ProfFan]

Ping @dellaert

[dellaert]

Convince me that this is the correct change. There is also an integration covariance mentioned in the paper. Are we sure this is not that? How is an initialization part of a parameter?

[varunagrawal]

PreintegrationParams has an integrationCovariance which is what is used for integration.

gtsam/gtsam/navigation/CombinedImuFactor.cpp

Line 149 in d48b1fc

const Matrix3& iCov = p().integrationCovariance;

In that same file, we have bInitCov which is assigned from p().biasAccOmegaInt.

gtsam/gtsam/navigation/CombinedImuFactor.cpp

Line 150 in d48b1fc

const Matrix6& bInitCov = p().biasAccOmegaInt;

biasAccOmegaInit should be the initial covariance for the 6 dimensional bias term encapsulating both the acceleration and angular velocity (aka ConstantBias) and is used by the CombinedImuFactor for preintegrating and propagating the bias covariance.

[dellaert]

Ok, you convinced me. But how could we make this change in a way that does not break existing user code?

[varunagrawal]

Ok, you convinced me. But how could we make this change in a way that does not break existing user code?

This has been the big question for me. I wonder if we can put in a deprecation warning like message that lets users know the variable name has changed? If we're cutting 4.3a as a new release, can we make an exception?

[dellaert]

Typically, we bracket in ifdefs, so we can do that here as well?