gtsam/examples/matlab/Pose2SLAMExample_easy.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 Simple robotics example using the pre-built planar SLAM domain
% @author Alex Cunningham
% @author Frank Dellaert
% @author Chris Beall
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%% Assumptions
%  - All values are axis aligned
%  - Robot poses are facing along the X axis (horizontal, to the right in images)
%  - We have full odometry for measurements
%  - The robot is on a grid, moving 2 meters each step

%% Create keys for variables
x1 = 1; x2 = 2; x3 = 3;

%% Create graph container and add factors to it
graph = pose2SLAMGraph;

%% Add prior
% gaussian for prior
prior_model = gtsamSharedNoiseModel_Sigmas([0.3; 0.3; 0.1]);
prior_measurement = gtsamPose2(0.0, 0.0, 0.0); % prior at origin
graph.addPrior(x1, prior_measurement, prior_model); % add directly to graph

%% Add odometry
% general noisemodel for odometry
odom_model = gtsamSharedNoiseModel_Sigmas([0.2; 0.2; 0.1]);
odom_measurement = gtsamPose2(2.0, 0.0, 0.0); % create a measurement for both factors (the same in this case)
graph.addOdometry(x1, x2, odom_measurement, odom_model);
graph.addOdometry(x2, x3, odom_measurement, odom_model);

%% Add measurements
% general noisemodel for measurements
meas_model = gtsamSharedNoiseModel_Sigmas([0.1; 0.2]);

% print
graph.print('full graph');

%% Initialize to noisy points
initialEstimate = pose2SLAMValues;
initialEstimate.insertPose(x1, gtsamPose2(0.5, 0.0, 0.2));
initialEstimate.insertPose(x2, gtsamPose2(2.3, 0.1,-0.2));
initialEstimate.insertPose(x3, gtsamPose2(4.1, 0.1, 0.1));

initialEstimate.print('initial estimate');

%% Optimize using Levenberg-Marquardt optimization with an ordering from colamd
result = graph.optimize(initialEstimate);
result.print('final result');