gtsam/matlab/examples/Pose2SLAMExample_circle.m

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% GTSAM Copyright 2010, Georgia Tech Research Corporation,
% Atlanta, Georgia 30332-0415
% All Rights Reserved
% Authors: Frank Dellaert, et al. (see THANKS for the full author list)
%
% See LICENSE for the license information
%
% @brief Read graph from file and perform GraphSLAM
% @author Frank Dellaert
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%% Create a hexagon of poses
hexagon = pose2SLAMValues.Circle(6,1.0);
p0 = hexagon.pose(0);
p1 = hexagon.pose(1);

%% create a Pose graph with one equality constraint and one measurement
fg = pose2SLAMGraph;
fg.addPoseConstraint(0, p0);
delta = p0.between(p1);
covariance = gtsamnoiseModelDiagonal.Sigmas([0.05; 0.05; 5*pi/180]);
fg.addRelativePose(0,1, delta, covariance);
fg.addRelativePose(1,2, delta, covariance);
fg.addRelativePose(2,3, delta, covariance);
fg.addRelativePose(3,4, delta, covariance);
fg.addRelativePose(4,5, delta, covariance);
fg.addRelativePose(5,0, delta, covariance);

%% Create initial config
initial = pose2SLAMValues;
initial.insertPose(0, p0);
initial.insertPose(1, hexagon.pose(1).retract([-0.1, 0.1,-0.1]'));
initial.insertPose(2, hexagon.pose(2).retract([ 0.1,-0.1, 0.1]'));
initial.insertPose(3, hexagon.pose(3).retract([-0.1, 0.1,-0.1]'));
initial.insertPose(4, hexagon.pose(4).retract([ 0.1,-0.1, 0.1]'));
initial.insertPose(5, hexagon.pose(5).retract([-0.1, 0.1,-0.1]'));

%% Plot Initial Estimate
figure(1);clf
plot(initial.xs(),initial.ys(),'g-*'); axis equal

%% optimize
result = fg.optimize(initial);

%% Show Result
hold on; plot(result.xs(),result.ys(),'b-*')
result.print(sprintf('\nFinal result:\n'));