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
A structure-from-motion problem on a simulated dataset
| def gtsam.examples.SFMExample.main |
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Camera observations of landmarks (i.e. pixel coordinates) will be stored as Point2 (x, y).
Each variable in the system (poses and landmarks) must be identified with a unique key.
We can either use simple integer keys (1, 2, 3, ...) or symbols (X1, X2, L1).
Here we will use Symbols
In GTSAM, measurement functions are represented as 'factors'. Several common factors
have been provided with the library for solving robotics/SLAM/Bundle Adjustment problems.
Here we will use Projection factors to model the camera's landmark observations.
Also, we will initialize the robot at some location using a Prior factor.
When the factors are created, we will add them to a Factor Graph. As the factors we are using
are nonlinear factors, we will need a Nonlinear Factor Graph.
Finally, once all of the factors have been added to our factor graph, we will want to
solve/optimize to graph to find the best (Maximum A Posteriori) set of variable values.
GTSAM includes several nonlinear optimizers to perform this step. Here we will use a
trust-region method known as Powell's Dogleg
The nonlinear solvers within GTSAM are iterative solvers, meaning they linearize the
nonlinear functions around an initial linearization point, then solve the linear system
to update the linearization point. This happens repeatedly until the solver converges
to a consistent set of variable values. This requires us to specify an initial guess
for each variable, held in a Values container.
Definition at line 29 of file SFMExample.py.