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Can a yaw offset exist between the utm and map frames when using robot_localization with GPS data?

asked 2022-02-14 15:50:54 -0500

Pepis gravatar image

updated 2023-01-15 08:42:14 -0500

ljaniec gravatar image

Hi! I'm using robot_localization to implement a GPS waypoint follower in nav2. For that I make use of the fromLL service to convert GPS coordinates into poses in the map frame.

From what I saw in the code, this sevice takes the GPS coordinates into the utm frame and later transforms them to the map frame assuming there is no rotation between them.

I picked up the work from someone else. He had pointed out that a yaw offset may exist between the utm and map frames which would cause the returned point to be placed on a rotated coordinate system not corresponding with the actual orientation of the latter, thus making the returned Cartesian point invalid.

However is my understanding that those frames have to both follow the ENU convention, meaning that both should have their +x axes pointing to the east

Can this offset exist? If that is the case, can the result of the FromLL service be invalid?

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answered 2023-01-22 08:55:21 -0500

Mike Scheutzow gravatar image

The yaw will be invalid if you provide bad data to the navsat node. You are responsible for telling navsat what the correct yaw is, because the raw GPS data is unable to provide this information. Please read the first sentence on this page:

The important phrase is "a sensor_msgs/Imu containing an accurate estimate of your robot’s heading".

The sensor_msgs/Imu you pass to navsat must specify the correct yaw (in the Imu frame.) For yaw, the navsat node is going to transform it into the map frame, and pass it back to you.

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Asked: 2022-02-14 15:50:54 -0500

Seen: 73 times

Last updated: Jan 22