Overlapping-Camera Calibration

1.Calibration List Page 
This page contains the list of calibrations. You can launch an existing dataset, delete and even manage your access to these datasets.
2. Overlapping-Camera Calibration Launch
You can select an existing Overlapping-camera calibration from the list page, or click on the “New Calibration” button on the top-right of the calibration list page and select the Overlapping-calibration in the window that pops.
3. Start Page
The page lists the important instructions and requirements that you need to follow in order to complete the calibration process.
Start the app by clicking on the “Get Started” button
Choose calibration method (Calibration target/ Targetless). 'Calibration target' method requires checkerboard images in the Overlapping field of view. 'Targetless' approach does not require a checkerboard.
Input the name you wish to give this calibration. This name will be shown on the calibration-list page. And then click on “Set Details”
4. Setup Overlapping-Camera details
You can fill in the basic details for the Overlapping-Camera and also specifically for the left and right camera of the Overlapping-camera.
Camera name: Input the name for the Overlapping-Camera sensor
Distance between left and right camera (m): Input the distance between the left and right camera in meters. (Applicable for targetless approach)
Camera lens model: Select the lens model of your Overlapping-Camera
Fill Camera intrinsic parameters manually: Check the box if you can input the intrinsic parameters for the left and right camera. Otherwise, uncheck it.
Left/Right Camera Intrinsic Parameters: The following parameters are common to both cameras.
Import Intrinsic Parameters: If you have calibrated the left and right cameras with the Deepen Camera-Intrinsic Calibration App and created profiles for your workspace, you can directly import the values using the dropdown menu. 
Import from JSON: You can use JSON files to import the intrinsics parameters as well.
Once all the details are filled in, click the “Save Changes” button on the top right to save the changes. After that, click the “Continue” button on the bottom right.
Calibration target camera details
Targetless calibration camera details
5. Add image pairs
You need to add the images taken from the left and right camera of the Overlapping-Camera. This page allows you to pair them manually. Also, it has an “Auto Pair” button to pair the files automatically, based on their filename order. It is recommended to follow the file naming guidelines from the Overlapping-Calibration Data collection doc.
Upload the images for the left camera
Upload the images for the right camera
Files are automatically paired based on the file name order.
Verify if the pairing is correct or not. If not, select the correct file pair on left and right, and pair them up using the “Add Pair” button on the bottom.
Delete any unpaired files, with the delete button that appears when hovered over a file.
Click on the “Save Changes” button to upload the files and save the pairing details for the files. After that, click on the “Continue” button.
Checkerboard image pairs
Targetless images
6. Set details
Checkerboard: Set checkerboard details 
You need to fill in the checkerboard details like Horizontal Corners, Vertical Corners and Dimensions i.e. square size for the checkerboard and click on “Set Config”. Then click on “Save Changes” and then click on Continue.
Square dimension should be in meters. And the horizontal and the vertical corners are inner corners of the checkerboard.
Targetless: Detect feature points
Click the "Detect" button to identify important point matches in the image pair. You can visualize the matches by following along the corresponding lines (Hover to highlight).
Go through the detected points and choose the best-detected matching point results from the dropdown. (If only one result set, then no action to take)  
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7. Calibrate
Checkerboard
On this page, you just have to click “Run Calibration” to get the calibration results. Once clicked, the images are processed and once done, the calibration results are shown on the right side of the page. Also, the Visualise button becomes enabled and allows you to visualise the calibration results.
Targetless
On this page, you just have to click “Run Calibration” to get the calibration results. Once clicked, the images are processed and once done, the calibration results are shown on the right side of the page. Also, the 'Visualise' button and the 'Display Epilines' checkbox becomes enabled and allow you to visualise the calibration results.
Targetless calibration epilines
Each epiline is the projection of the corresponding point from the opposite image. Hence, the quality of the calibration can be judged by how close the epilines are to the corresponding points. Also, all the epilines in one image converge to the epipole (could be outside the image). For convenience, you can see the 'Epiline point distance' (average distance of the point to its respective epiline) error stat.
8. Error stats
You can toggle the error stats and select individual errors or average errors. Individual Errors show the errors related to an image pair selected on the left pane. 
Checkerboard
Left Reprojection Error: The pixel error when the detected corners from the right image are projected onto the left image using the calibration results
Right Reprojection Error: The pixel error when the detected corners from the left image are projected onto the right image using the calibration results
Translation Error: The distance between the means of the 3d projections of the checkerboard in a 3d scene from the left images and right images
Rotation Error: The angle between the planes of the 3d projections in a 3d scene of the checkerboard from the left images and right images
Targetless
Epiline Point Distance: Average pixel distance of each point to its corresponding projected epiline.
Epipolar Error: Proportional to the distance of a point from its epiline. Does not have a physical meaning. It is the residual error from minimizing the epipolar constraints while calculating the fundamental/essential matrix
9. Visualise
Clicking on the visualise button takes you to the visualisation screen. You can see the cameras and the selected image-pair checkerboard on the screen. You can move around in the 3d scene using the mouse left (for pan) or right (for orbit) button click-drag, to have a better sense of the view. Also, on the top-right, in the options dropdown, you have the option to show/hide all the checkerboards from all the image pairs at once.
Only frustums are visible for Targetless method.
Visualization for Target based approach
Visualization for Targetless based approach
10. Export
You can export the results of the calibration using the “Export” button on the top-right of the page. Fill in the name of the output file and click on Export.

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Data Collection for Overlapping-Camera Calibration

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