Refactor and optimize alignment and density map code

[saurabh1002]

This pull request introduces several improvements and refactorings to the map closure and ground alignment modules. The main code changes enhance code clarity, numerical stability, and maintainability, particularly in the 2D RANSAC alignment and ground alignment logic.

Summary of most important changes:

Refactoring and Code Improvements

• Refactored KabschUmeyamaAlignment2D in AlignRansac2D.cpp to use operator overloading for PointPair and improved mean and covariance calculations, leading to clearer and more robust code. Added operator+ and operator/ to PointPair in AlignRansac2D.hpp.
• Improved RANSAC logic in AlignRansac2D.cpp by parameterizing sample size with min_points, using squared distance for inlier checks, and making variable types more explicit.

Ground Alignment Enhancements

• Refactored GroundAlign.cpp to define algorithm parameters as constexpr, improved normal filtering, and enhanced numerical stability and early returns for degenerate cases. Improved the linear system construction and main alignment loop for clarity and correctness.

Density Map Calculation Improvements

• Fixed 2D discretization in DensityMap.cpp to correctly use 2x3 and 2x1 matrix blocks and improved pixel counting logic for better numerical accuracy.

Copyright and License Updates

• Updated copyright statements in all source and CMake files to only include "Saurabh Gupta" and changed the year to 2026.

[Copilot]

Pull request overview

This PR refactors and tightens the map-closure pipeline across C++ (alignment / ground alignment / density maps) and Python (pipeline, datasets), alongside packaging metadata and license header updates.

Changes:

• Refactors 2D RANSAC alignment, ground alignment, voxel map, and density-map discretization logic for clearer math and reduced overhead.
• Updates Python pipeline outputs (saving ground alignment transforms + HBST database) and shifts quaternion handling from pyquaternion to scipy.
• Updates packaging metadata (Python version floor, dependency pinning, classifiers) and refreshes copyright/license headers.

Reviewed changes

Copilot reviewed 37 out of 37 changed files in this pull request and generated 10 comments.

Show a summary per file

File	Description
python/pyproject.toml	Updates packaging metadata, Python version requirement, dependency ranges, and classifiers.
python/map_closures/voxel_map.py	Updates license header.
python/map_closures/visualizer/visualizer.py	Updates license header.
python/map_closures/visualizer/registration_visualizer.py	Updates license header.
python/map_closures/visualizer/local_maps_visualizer.py	Updates license header.
python/map_closures/visualizer/closures_visualizer.py	Updates license header.
python/map_closures/tools/utils.py	Adds MIT license header to utilities module.
python/map_closures/tools/evaluation.py	Adjusts evaluation reporting/table formatting and typing.
python/map_closures/tools/cmd.py	Updates license header.
python/map_closures/tools/init.py	Updates license header.
python/map_closures/pybind/map_closures_pybind.cpp	Updates license header.
python/map_closures/pybind/CMakeLists.txt	Updates license header.
python/map_closures/pipeline.py	Renames variables for clarity; adds persisted outputs (ground transforms, database) and richer console reporting.
python/map_closures/map_closures.py	Updates license header.
python/map_closures/datasets/ncd.py	Switches quaternion-to-rotation conversion to SciPy.
python/map_closures/datasets/helipr.py	Adds .ply support via Open3D and keeps .bin fallback.
python/map_closures/datasets/apollo.py	Switches quaternion-to-rotation conversion to SciPy.
python/map_closures/config/config.py	Updates license header.
python/map_closures/config/init.py	Updates license header.
python/map_closures/init.py	Updates license header.
python/LICENSE	Updates copyright line.
python/CMakeLists.txt	Updates license header.
cpp/map_closures/VoxelMap.hpp	Refactors constants and introduces precomputed sqrt for map resolution.
cpp/map_closures/VoxelMap.cpp	Refactors mean/covariance computation and container usage for efficiency/clarity.
cpp/map_closures/MapClosures.hpp	Refactors closure retrieval and adds a persistent BFMatcher member.
cpp/map_closures/MapClosures.cpp	Refactors ORB self-matching flow and improves top-k selection logic.
cpp/map_closures/GroundAlign.hpp	Updates license header.
cpp/map_closures/GroundAlign.cpp	Refactors ground sampling/filtering, linear system construction, and optimization loop.
cpp/map_closures/DensityMap.hpp	Updates license header.
cpp/map_closures/DensityMap.cpp	Fixes 2D discretization blocks and improves pixel counting logic.
cpp/map_closures/CMakeLists.txt	Updates license header.
cpp/map_closures/AlignRansac2D.hpp	Adds PointPair operators to simplify accumulation logic.
cpp/map_closures/AlignRansac2D.cpp	Refactors mean/covariance and inlier checks; parameterizes sample size.
cpp/LICENSE	Updates copyright line.
cpp/CMakeLists.txt	Updates license header.
cpp/3rdparty/find_dependencies.cmake	Updates license header.
LICENSE	Updates copyright line.

Comments suppressed due to low confidence (1)

python/map_closures/tools/evaluation.py:112

• rich.Table needs columns defined before calling add_row. Since all add_column(...) calls were removed, this will raise at runtime (or render incorrectly). Re-introduce the column definitions (and optionally the caption) so the table structure matches the rows being added.

    def _rich_table_pr(self, table_format: box.Box = box.HORIZONTALS) -> Table:
        table = Table(box=table_format)
        for i, metric in enumerate(self.metrics):
            table.add_row(
                f"{i + 3} {metric.tp} {metric.fp} {metric.fn} {metric.precision:.4f} {metric.recall:.4f} {metric.F1:.4f}"
            )

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