TigerMX-5 Settings > Camera Calibration
Camera Calibration
About This Page
Background
In order to accurately detect (and display) objects in their environment, Black Moth cameras need to be calibrated both intrinsically and extrinsically.
- Intrinsic calibration is for parameter modelling within the camera (i.e. the lens, its position w.r.t the image sensor, and the mechanicals and tolerances). It helps build a model of consistency between cameras so objects and distances can be measured accurately.
- Extrinsic calibration is for parameter modelling between cameras (i.e. when stitching imagery together, or relating objects from one camera's view to another camera's view).
Page Information
This page shows details about the calibration status of each camera and provides the options for performing intrinsic and extrinsic calibration. This includes Intrinsic Calibration and April Tag Snapshots.
This information is also available for distribution to customers and installers as a deployment work instruction DWI-0014 - Work Instruction - Top View Enablement
A developer support guide for Manual April Tag Calibration also exists on Confluence for manual (offline) stitching of extrinsic April Tag snapshots in cases where the automatic calibration fails to pickup the April Tags. This is particularly common on large vehicles like Mining Excavators.
Accessing This Page
This page can be accessed from:
Page View
Page Usage
Use this page to navigate to Intrinsic Calibration and April Tag Snapshots pages by pressing their respective buttons. Details about the calibration status of each camera is also visible, with hints to getting calibration complete.
Intrinsic Calibration
Intrinsic calibration should be done by Black Moth before you receive cameras, however there are cases whereby the cameras require re-calibration; cameras may have been deployed prior to calibration, or the calibration technique may have improved.
About This Page
This page provides the controls for calibrating a unit's cameras' intrinsic properties. This will ensure the GUI view is correct for a given camera.
The calibration is performed by following steps 4-8 of DWI-0014 - Work Instruction - Top View Enablement.
Accessing This Page
This page can be accessed from:
Page View
Camera Select
Unselected
Selected
Calibrating
Page Usage
Camera Select
Use this view to select the cameras requiring calibration. Cameras that are already calibrated can be re-calibrated if desired. Use the check box on the right to select cameras and press Calibrate to start Calibrating.
Calibrating
This view shows the status of each camera's calibration. Press CANCEL to stop calibration for the respective camera.
April Tag Snapshots
About This Page
This page is used to perform April Tag calibration, which improves image stitching (for Top View / Dome View) and refines extrinsic properties.
The calibration is performed by following steps 9-18 of DWI-0014 - Work Instruction - Top View Enablement.
Accessing This Page
This page can be accessed from:
Page View
Default Page
No snapshots available
With snapshots
Extrinsic Calibration Parameters Prompt
Edit Snapshots
No snapshots available
With snapshots
April Tag Position Prompt
Page Usage
Default page
This is the default page of the April Tag Snapshots. If April Tag Snapshots has not been run previously, snapshots have been cleared, or if snapshots have disappeared (see info below) the screen will display No snapshots available. Press Edit Snapshots to capture new, or edit existing April Tag Snapshots, this will lead to the Extrinsic Calibration Parameters Prompt.
Extrinsic Calibration Parameters Prompt
The Extrinsic Calibration Parameters Prompt is used to set the following parameters:
- Apriltag Width - Width of the April Tag in meters.
- Reference Camera - Camera to be subject to pose calibration.
- Reference Camera Yaw - Yaw of the reference camera in degrees.
Press OK to continue to Edit Snapshots or CANCEL to return to the Default Page.
Edit Snapshots
The Edit Snapshots view has the following controls:
- Cancel - Cancel changes and return to Default Page.
- Delete All - Deletes all listed snapshots.
- Capture Snapshots - Initiate capture of each camera in new snapshot (opens April Tag Position Prompt).
- Save Changes - Save changes and return to Default Page.
- X (on each snapshot With snapshots) - Delete the respective snapshot.
April Tag Position Prompt
April Tags are intended to be lay flat on the ground to enable the calibration to refine the camera pose properties. If there are situations where this is not possible, this prompt allows users to skip the pose calibration and focus on improving image stitching.
"Are all the April tags flat on the ground?":
- Yes - Calibrate for camera pose and image stitching
- No - Calibrate for image stitching only
Following the April Tag Position Prompt, the Tiger will then detect the presence of April Tags, and calibrate the camera positions accordingly.
Disappearance of snapshots: Some events may lead to the absence or disappearance of April Tag Snapshots. Known events are changes to the cameras table (ie. a camera has been replaced), which causes the respective camera snapshots to disappear until the new camera has finished syncing its information with the Tiger (which happens just before the camera begins streaming). Other causes may be related to saving, where the Tiger is shutdown or the view is exited without pressing Save Changes.
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