A bug for coordinate transform

[hzdsdhr]

Hi, I think there is a bug for coordinate transform in lidar_process, check the code in lidar_process.cpp 255~260(bool LidarProcess::GetSensorTrans(const double query_time, Matrix4d* trans)):
try {
tf2_listener_.lookupTransform(FLAGS_lidar_tf2_frame_id,
FLAGS_lidar_tf2_child_frame_id, query_stamp, stamped_transform);
} catch (tf2::TransformException& ex) {
AERROR << "Exception: " << ex.what();
return false;
}
This function trys to get the sensor's pose and location to transform all the objects into a global coordinate like /world for latter tracking. So "FLAGS_lidar_tf2_child_frame_id" should be like "velodyne"(or something like that), and "FLAGS_lidar_tf2_frame_id" should be a global frame like "/world". But by checking gflags file perception_gflags.cc in src/perception/apollo_perception_ros/src/common/, I found this:
DEFINE_string(lidar_tf2_frame_id, "base_link", "the tf2 transform frame id");
DEFINE_string(lidar_tf2_child_frame_id, "velodyne64",
"the tf2 transform child frame id");
So FLAGS_lidar_tf2_frame_id is "base_link". First of all, there is no such frame in Apollo. Apollo's frame is like:velodyne64->novatel->world. Second, by reading other code, the base_link is more like vehicle body frame.
So This transform won't transform objects in velodyne frame into world frame but the base_link(vehicle frame). This is not correct for tracking, because tracking should happen in a fix(not moving) frame.
Please check and tell me if I'm right or not.

[hzdsdhr]

@cedricxie can you take a look and feed back? Thank you.