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Fusing absolute pose data

asked 2014-12-23 16:02:47 -0500

Shokoofeh gravatar image

As I understand, in the robot_localization state estimation node, the differential parameter should be set to false if sensor contains absolute pose information. However, in this robot_localization tutorial, in section 2.1.1, it's stated that "If fusing absolute pose data (position or rotation), you will most likely want to set the sensor's differential parameter to true. "

Assuming that absolute position and/or orientation information is coming from only one source, is there any reason that we should set the differential parameter to true?

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answered 2014-12-29 10:25:05 -0500

Tom Moore gravatar image

The only reason to set the differential parameter to true if you only have one source of pose and/or orientation data is to ensure that the output of the state estimate starts at 0. For example, if your input pose data starts at (10, 23), then using the differential parameter will make sure the output position still starts at (0, 0). This is actually more important for orientation from IMUs, as the orientation is probably not going to align with your world frame (i.e., it will not start at 0).

In any case, the intended use for the differential parameter was to allow for multiple independent measurements of absolute pose/orientation data. I should clarify this in the tutorial.

One exception: GPS data or measurements of absolute position estimates resulting from, for example, landmark observations should also not be fused differentially.

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Update on this: a forthcoming version will add a xxx_relative parameter, which can be used to fuse data absolutely (i.e., non-differentially), but will still allow it to start at 0.

Tom Moore gravatar image Tom Moore  ( 2015-03-10 15:46:15 -0500 )edit

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Asked: 2014-12-23 16:02:47 -0500

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Last updated: Dec 29 '14