IMU to Camera constraint?

[lowellm91]

Hi, I have an IMU and a Stereo Camera and some calibration information, I'm a little bit confused on how you create constraints between these two sensors. It could be modeled as a pose constraint with a really low variance but I would rather enforce an equality constraint between them(ex IMU_pose_(t_1) = T*(cam_pose_(t_1))

[ProfFan]

I think you can use the body_T_sensor of the IMUFactor

[lowellm91]

Hi Thanks, I was looking at the documentation and that doesn't appear to exist.

https://gtsam.org/doxygen/4.0.0/a03467.html

I must be missing something.

[scott-robotics]

The local transform / extrinsic between the sensors is handled in the Preintegration routine (via PreintegratedRotationParams).

gtsam::imuBias::ConstantBias prior_imu_bias;  // assume zero initial bias

auto parameters = gtsam::PreintegratedCombinedMeasurements::Params::MakeSharedD(0.0);
parameters->setBodyPSensor(local_transform); // <- Put your calibration info here
auto preintegration = std::make_shared<gtsam::PreintegratedImuMeasurements>(parameters, prior_imu_bias);

Here's an example using IMU preintegration: https://github.com/borglab/gtsam/blob/develop/examples/ImuFactorsExample.cpp