difference between linear_acceleration and linear_acceleration_vrf

[apycii]

Hello guys!

I have two questions in this proto file.

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apollo/modules/localization/proto/pose.proto

package apollo.localization;

import "modules/common/proto/geometry.proto";

message Pose { // Position of the vehicle reference point (VRP) in the map reference frame. // The VRP is the center of rear axle. optional apollo.common.PointENU position = 1;

// A quaternion that represents the rotation from the IMU coordinate // (Right/Forward/Up) to the // world coordinate (East/North/Up). optional apollo.common.Quaternion orientation = 2;

// Linear velocity of the VRP in the map reference frame. // East/north/up in meters per second. optional apollo.common.Point3D linear_velocity = 3;

// Linear acceleration of the VRP in the map reference frame. // East/north/up in meters per second. optional apollo.common.Point3D linear_acceleration = 4;

// Angular velocity of the vehicle in the map reference frame. // Around east/north/up axes in radians per second. optional apollo.common.Point3D angular_velocity = 5;

// Heading // The heading is zero when the car is facing East and positive when facing North. optional double heading = 6;

// Linear acceleration of the VRP in the vehicle reference frame. // Right/forward/up in meters per square second. optional apollo.common.Point3D linear_acceleration_vrf = 7;

// Angular velocity of the VRP in the vehicle reference frame. // Around right/forward/up axes in radians per second. optional apollo.common.Point3D angular_velocity_vrf = 8;

// Roll/pitch/yaw that represents a rotation with intrinsic sequence z-x-y. // in world coordinate (East/North/Up) // The roll, in (-pi/2, pi/2), corresponds to a rotation around the y-axis. // The pitch, in [-pi, pi), corresponds to a rotation around the x-axis. // The yaw, in [-pi, pi), corresponds to a rotation around the z-axis. // The direction of rotation follows the right-hand rule. optional apollo.common.Point3D euler_angles = 9; }

---

Isn`t linear_acceleration unit meter per square second?

also,

What`s difference between linear_acceleration and linear_acceleration_vrf ? only the direction?

[InterKnight]

VRP means Vehicle Reference Point. So linear_acceleration is in global coordinate and linear_acceleration_vrf is in vehicle coordinate