# Tangram Vision Documentation

> Use MetriCal for accurate, precise, and expedient calibration of multimodal sensor suites


## metrical


### calibration_guides

- [Camera ↔ IMU Calibration Guide](/metrical/calibration_guides/camera_imu_cal.md): This file explains IMU calibration with MetriCal, which requires no specific targets since IMUs measure forces and velocities directly, and must be performed alongside camera calibration.
- [Camera ↔ LiDAR Calibration Guide](/metrical/calibration_guides/camera_lidar_cal.md): This file provides a comprehensive guide for calibrating camera-LiDAR sensor pairs using MetriCal, including both combined and staged calibration approaches with circular targets.
- [Calibration Guide Overview](/metrical/calibration_guides/guide_overview.md): This file provides general calibration principles and guidelines that apply to all MetriCal calibration scenarios, including target selection, data quality considerations, and sensor-specific guidance.
- [LiDAR ↔ LiDAR Calibration Guide](/metrical/calibration_guides/lidar_lidar_cal.md): This file provides a guide for calibrating multiple LiDAR sensors together using MetriCal with circle targets and includes a practical example dataset.
- [Camera ↔ LNS Guide](/metrical/calibration_guides/local_navigation_cal.md): This file provides a guide for for calibrating local navigation systems using MetriCal and includes a practical example dataset.
- [Multi-Camera Calibration Guide](/metrical/calibration_guides/multi_camera_cal.md): This file provides guidance for multi-camera calibration in MetriCal, covering both combined and staged approaches for calibrating camera intrinsics and extrinsics simultaneously.
- [Narrow Field-of-View Camera Calibration](/metrical/calibration_guides/narrow_fov_cal.md): This file provides an outline of the procedure of calibrating narrow field-of-view cameras with multiple target boards using metrical
- [Single Camera Calibration Guide](/metrical/calibration_guides/single_camera_cal.md): This file provides tips and best practices for single camera calibration using MetriCal, including basic workflows and techniques for seeding larger multi-stage calibrations.

### calibration_models

- [Camera Models](/metrical/calibration_models/cameras.md): This file documents all supported camera intrinsics models in MetriCal, including pinhole, distortion models, and fisheye lenses with their respective parameters and mathematical descriptions.
- [IMU Models](/metrical/calibration_models/imu.md): This file documents all supported IMU intrinsics models in MetriCal for calibrating accelerometer and gyroscope measurements with their mathematical modeling and correction processes.
- [LiDAR Models](/metrical/calibration_models/lidar.md): This file documents the supported LiDAR models in MetriCal, which currently focuses on extrinsics calibration since LiDAR intrinsics are typically reliable from the factory.
- [Local Navigation System Models](/metrical/calibration_models/local_navigation.md): This file documents the local navigation systems calibration model in MetriCal.

### changelog

This file contains the comprehensive release notes and changelogs for MetriCal versions, documenting new features, bug fixes, breaking changes, and version-specific improvements.

- [Releases + Changelogs](/metrical/changelog.md): This file contains the comprehensive release notes and changelogs for MetriCal versions, documenting new features, bug fixes, breaking changes, and version-specific improvements.

### commands

- [MetriCal Command: Calibrate](/metrical/commands/calibration/calibrate.md): This file documents the MetriCal calibrate command, which performs full bundle adjustment calibration of multi-modal sensor systems using pre-recorded data, plex configuration, and object space definitions.
- [MetriCal Command: Consolidate](/metrical/commands/calibration/consolidate.md): This file documents the MetriCal consolidate object spaces command, which combines multiple object spaces into a single unified configuration using object relative extrinsics.
- [MetriCal Command: Init](/metrical/commands/calibration/init.md): This file documents the MetriCal init command, which creates uncalibrated plex files from datasets by inferring components, spatial constraints, and temporal constraints.
- [Focus](/metrical/commands/calibration/shape/shape_focus.md): This file documents the MetriCal shape focus command, which creates hub-and-spoke plex configurations where all components are spatially connected to one focus component.
- [Lookup Table](/metrical/commands/calibration/shape/shape_lut.md): This file documents the MetriCal shape LUT command, which creates pixel-wise lookup tables for single camera distortion correction and image undistortion.
- [Stereo Lookup Table](/metrical/commands/calibration/shape/shape_lut_stereo.md): This file documents the MetriCal shape stereo LUT command, which creates pixel-wise lookup tables for stereo camera pair rectification and stereo vision applications.
- [Minimum Spanning Tree](/metrical/commands/calibration/shape/shape_mst.md): This file documents the MetriCal shape MST command, which creates a plex containing only the minimum spanning tree of spatial components with optimal covariance connections.
- [Shape Mode](/metrical/commands/calibration/shape/shape_overview.md): This file provides an overview of MetriCal's shape command, which transforms plex files into various useful output formats for practical deployment and system integration.
- [Tabular](/metrical/commands/calibration/shape/shape_tabular.md): This file documents the MetriCal shape tabular command, which exports intrinsic and extrinsic calibration data from plex files in simplified table-based formats.
- [URDF](/metrical/commands/calibration/shape/shape_urdf.md): This file documents the MetriCal shape URDF command, which creates ROS-compatible URDF files from plex configurations for robotic system integration.
- [MetriCal Command: Completion](/metrical/commands/cli_utilities/completion.md): This file describes how to generate shell auto-completion scripts for MetriCal across different shell environments including bash, fish, elvish, powershell, and zsh.
- [MetriCal Command: Display](/metrical/commands/cli_utilities/display.md): This file documents the MetriCal display command, which visualizes calibration results applied to datasets using Rerun for ocular validation of calibration quality.
- [MetriCal Command: Report](/metrical/commands/cli_utilities/report.md): This file documents the MetriCal report command, which generates comprehensive calibration
reports from plex files or calibration output files in human-readable formats.
- [Errors & Troubleshooting](/metrical/commands/command_errors.md): This file catalogs MetriCal's error codes and exit codes with descriptions and troubleshooting steps for various operational failures and system issues.
- [MetriCal Commands](/metrical/commands/commands_overview.md): This file provides an overview of all MetriCal commands including init, calibrate, report, display, shape, and their universal options and usage patterns.
- [Global Arguments](/metrical/commands/global_arguments.md): This file provides an overview of the global arguments available in MetriCal commands.
- [Manifest Overview](/metrical/commands/manifest/manifest_overview.md): This file explains what a manifest is and how it is used in MetriCal.
- [MetriCal Command: New](/metrical/commands/manifest/new.md): This file describes how to create a new MetriCal manifest with default configuration.
- [MetriCal Command: Run](/metrical/commands/manifest/run.md): This file describes how to run a MetriCal manifest.
- [MetriCal Command: Validate](/metrical/commands/manifest/validate.md): This file describes how to validate a MetriCal manifest for correctness.

### configuration

- [Plans and Billing](/metrical/configuration/billing.md): This file explains how to create, cancel, and manage MetriCal subscriptions, payment methods, and billing contact information through the Tangram Vision Hub.
- [Valid Data Formats](/metrical/configuration/data_formats.md): This file documents the supported data formats in MetriCal including MCAP files, ROS bags, folder datasets, and their respective message encodings and requirements.
- [Installation](/metrical/configuration/installation.md): This file provides installation instructions for MetriCal via apt repository for Ubuntu/Pop!_OS systems and via Docker for other operating systems.
- [License Creation](/metrical/configuration/license_creation.md): This file explains how to create personal and group licenses for MetriCal through the Tangram Vision Hub, including license naming, creation, and revocation procedures.
- [License Usage](/metrical/configuration/license_usage.md): This file provides comprehensive instructions for using MetriCal license keys, including command line arguments, environment variables, configuration files, and offline licensing options.
- [Organization Management](/metrical/configuration/organizations.md): This file explains organization management in the Tangram Vision Hub, including how to name organizations, add members, assign roles, and manage organizational permissions for MetriCal usage.
- [Visualization](/metrical/configuration/visualization.md): This file explains how to set up and use MetriCal's visualization features with Rerun for visual inspection of calibration data, detections, and spatial alignment verification.

### core_concepts

- [Components](/metrical/core_concepts/components.md): This file defines components as atomic sensing units in MetriCal's Plex system, detailing camera, LiDAR, IMU, and LNS component types with their intrinsic parameters and modeling approaches.
- [Constraints](/metrical/core_concepts/constraints.md): This file defines constraints as spatial relations, temporal relations, or formations between components in MetriCal's Plex system, explaining directional conventions and extrinsic transformations.
- [Covariance](/metrical/core_concepts/covariance.md): This file explains covariance as a measure of uncertainty in MetriCal's Plex system, differentiating it from binary fixed/variable parameters and providing statistical modeling capabilities.
- [Object Space](/metrical/core_concepts/object_space_overview.md): This file explains MetriCal's Object Space concept, which refers to known sets of features in the environment used for cross-modality calibration and establishing metric scale.
- [Plex](/metrical/core_concepts/plex_overview.md): This file explains MetriCal's Plex concept, which represents the spatia relations, temporal relations, and formations within perception systems as a graph of components and constraints.
- [Projective Compensation](/metrical/core_concepts/projective_compensation.md): This file explains projective compensation, a phenomenon where errors in one calibration parameter affect other parameters due to correlation in observations or poor model choices.

### intro

This file introduces MetriCal, a tool for accurate and precise calibration of multimodal sensor suites with support for cameras, LiDAR, IMU sensors, and various calibration targets.

- [Welcome to MetriCal](/metrical/intro.md): This file introduces MetriCal, a tool for accurate and precise calibration of multimodal sensor suites with support for cameras, LiDAR, IMU sensors, and various calibration targets.

### results

- [MetriCal Results MCAP](/metrical/results/output_file.md): This file documents MetriCal's MCAP output format containing optimized plex data, object space
information, and detailed calibration metrics.
- [Binned Feature Counts](/metrical/results/pre_calibration_metrics/binned_feature_counts.md): Documents the binned feature counts pre-calibration metric
- [Circle Coverage](/metrical/results/pre_calibration_metrics/circle_coverage.md): Documents the circle coverage pre-calibration metric
- [Topic Filter Statistics](/metrical/results/pre_calibration_metrics/topic_filter_statistics.md): Documents the topic filter statistics pre-calibration metric
- [MetriCal Reports](/metrical/results/report.md): This file explains MetriCal's comprehensive calibration reports, including charts, diagnostics,
metrics interpretation, and HTML report generation for calibration quality assessment.
- [Circle Edge Misalignment](/metrical/results/residual_metrics/circle_edge_misalignment.md): This file explains circle edge misalignment metrics unique to MetriCal, which measure the bridging
between camera 2D features and LiDAR 3D point clouds using circular calibration targets
(specifically, this is about the edge misalignment cost).
- [Circle Misalignment](/metrical/results/residual_metrics/circle_misalignment.md): This file explains circle misalignment metrics unique to MetriCal, which measure the bridging between camera 2D features and LiDAR 3D point clouds using circular calibration targets.
- [Composed Relative Extrinsics](/metrical/results/residual_metrics/composed_relative_extrinsics.md): This file documents composed relative extrinsics error metrics in MetriCal, which measure consistency between relative extrinsics formed through object spaces and direct component transforms.
- [Differenced Pose Trajectory Error](/metrical/results/residual_metrics/differenced_pose_trajectory_error.md): This file explains differenced pose trajectory errors in MetriCal, which is the error in
aligning two different pose trajectories over the data capture period.
- [Image Reprojection](/metrical/results/residual_metrics/image_reprojection.md): This file explains image reprojection error metrics in MetriCal, which measure the precision of camera calibration by comparing feature positions in images to their object space counterparts.
- [IMU PreIntegration Error](/metrical/results/residual_metrics/imu_preintegration_error.md): This file documents IMU preintegration error metrics in MetriCal, which measure the consistency of IMU measurements across preintegration windows defined by navigation states.
- [Interior Points to Plane Error](/metrical/results/residual_metrics/interior_points_to_plane_error.md): This file explains interior points to plane error metrics in MetriCal, which measure the fit between LiDAR points detected on circular target surfaces and the actual target plane.
- [Object Inertial Extrinsics Error](/metrical/results/residual_metrics/object_inertial_extrinsic_error.md): This file explains object inertial extrinsics error metrics in MetriCal, which measure errors between sequences of measured and optimized extrinsics involving IMU navigation states.
- [Paired 3D Point Error](/metrical/results/residual_metrics/paired_3d_point_error.md): This file documents paired 3D point error metrics in MetriCal, which measure LiDAR alignment
quality by comparing detected circle centers between different LiDAR frames of reference.
- [Paired Plane Normal Error](/metrical/results/residual_metrics/paired_plane_normal_error.md): This file documents paired plane normal error metrics in MetriCal, which measure LiDAR alignment quality by comparing detected plane normals of circle targets between LiDAR frames of reference.

### special_topics

- [Calibrate RealSense Sensors](/metrical/special_topics/calibrate_realsense.md): This file provides a tutorial for calibrating multiple Intel RealSense sensors simultaneously using MetriCal, including data recording procedures and calibration flashing.
- [Migrate from Kalibr to MetriCal](/metrical/special_topics/kalibr_to_metrical_migration.md): This file provides a comprehensive guide for migrating calibration workflows from Kalibr to MetriCal, highlighting operational differences and improved capabilities.

### support_and_admin

- [Contact Us](/metrical/support_and_admin/contact.md): This file provides contact information for MetriCal user support, partnering inquiries, and citation guidelines for academic research.
- [Legal Information](/metrical/support_and_admin/legal.md): This file contains legal disclaimers, confidentiality notices, and comprehensive third-party license information for the Tangram Vision Platform and MetriCal software.

### targets

- [Camera Targets](/metrical/targets/camera_targets.md): This file documents all supported calibration targets in MetriCal including AprilGrid, markerboards, checkerboards, and LiDAR circle targets with their specifications and usage guidelines.
- [Combining Modalities](/metrical/targets/combining_modalities.md): This file documents how to combinne multiple modalities simultaneously in MetriCal using different target types.
- [LiDAR Targets](/metrical/targets/lidar_targets.md): This file documents all supported calibration targets in MetriCal for LiDAR with their specifications and usage guidelines.
- [Using Multiple Targets](/metrical/targets/multiple_targets.md): This file explains how to use multiple calibration targets simultaneously in MetriCal, including object space configuration, UUID generation, and target positioning for complex setups.
- [Target Construction Guide](/metrical/targets/target_construction.md): This file provides comprehensive guidance on constructing calibration targets for MetriCal, including target selection, printing considerations, and quality control measures.
- [Target Overview](/metrical/targets/target_overview.md): This file explains the different types of calibration targets supported by MetriCal.