edgeConstraints

Edge constraints in pose graph

Description

measurements = edgeConstraints(poseGraph) lists all edge constraints in the specified pose graph as a relative pose.

[measurements,infoMats] = edgeConstraints(poseGraph) also returns the information matrices for each edge. The information matrix is the inverse of the covariance of the pose measurement.

[measurements,infoMats] = edgeConstraints(poseGraph,edgeIDs) returns edge constraints for the specified edge IDs.

Input Arguments

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Pose graph, specified as a poseGraph or poseGraph3D object.

Edge IDs, specified as a vector of positive integers.

Output Arguments

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Measurements between nodes, returned as an n-by-3 matrix or n-by-7 matrix.

For poseGraph (2-D), each row is an [x y theta] vector, which defines the relative xy-position and orientation angle, theta, of a pose in the graph. For landmark positions, theta is returned as NaN.

For poseGraph3D, each row is an [x y z qw qx qy qz] vector, which defines the relative xyz-position and quaternion orientation, [qw qx qy qz], of a pose in the graph.

Note

Many other sources for 3-D pose graphs, including .g2o formats, specify the quaternion orientation in a different order, for example, [qx qy qz qw]. Check the source of your pose graph data before adding nodes to your poseGraph3D object.

Information matrices, specified in compact form as a n-by-6 or n-by-21 matrix, where n is the number of poses in the pose graph.

Each row is the upper triangle of the square information matrix. An information matrix represents the uncertainty of the measurement. The matrix is calculated as the inverse of the covariance. If the measurement is an [x y theta] vector, the covariance matrix is a 3-by-3 of pairwise covariance calculations. Typically, the uncertainty is determined by the sensor model.

For poseGraph (2-D), each information matrix is a six-element vector. The default is [1 0 0 1 0 1]. For landmark nodes, the last three elements are returned as NaN.

For poseGraph3D, each information matrix is a 21-element vector. The default is [1 0 0 0 0 0 1 0 0 0 0 1 0 0 0 1 0 0 1 0 1].