Calibrated camera format¶

This format defines the calibrated cameras (output of calibration).

Definitions¶

Sensor: A sensor is a model of a physical imaging sensor, typically a combination of a sensing chip (like a CCD or CMOS) and a lens. It is described by its type and internal parameters. It contains both the initial and the optimized internal parameters, as well as rig relatives if applicable.
Camera: A camera represents an instance of a shot taken by a sensor, with a given pose. It contains geolocation (an initial pose estimate from GPS and IMU) if applicable, the optimized pose, and the optimized rolling shutter parameters if applicable.

Coordinate system specification¶

Same as the projected camera coordinate system specification

Format specification¶

Specification format	Version
“application/opf-calibrated-cameras+json”	“1.0”

Calibrated cameras¶

Definition of Calibrated Camera Parameters

Calibrated cameras Properties

	Type	Description	Required
format	`string`	For calibrated cameras it must be `"application/opf-calibrated-cameras+json"`	✓ Yes
version	`string`	The version of this schema as `MAJOR.MINOR`. Breaking changes are reflected by a change in MAJOR version. Can optionally include a pre-release tag `MAJOR.MINOR-tag`. Examples: `0.1`, `1.0`, `1.0-draft1`	✓ Yes
sensors	`sensor` `[]`	Calibrated sensor parameters.	✓ Yes
cameras	`camera` `[]`	Calibrated camera parameters.	✓ Yes
extensions	`object`	JSON object with extension-specific objects. Extensions follow the naming convention VENDOR[_(team❘product)]_extname	No

Calibrated camera¶

Calibrated camera Properties

	Type	Description	Required
id	`integer`	Unique ID of the camera, it must appear in the input cameras.	✓ Yes
sensor_id	`integer`	Unique ID of the sensor used by this camera.	✓ Yes
position	`number` `[3]`	Calibrated coordinates in the processing CRS.	✓ Yes
orientation_deg	`number` `[3]`	Calibrated Omega-Phi-Kappa angles in degree representing a rotation R_x(ω)R_y(ϕ)R_z(κ) from the image CS to the processing CRS.	✓ Yes
rolling_shutter	`number` `[3]`	Refer to this document.	No
extensions	`object`	JSON object with extension-specific objects. Extensions follow the naming convention VENDOR[_(team❘product)]_extname	No

Calibrated rig relatives¶

Calibrated rig relatives contain the optimised relative translations and rotations in processing CRS units.

Calibrated rig relatives Properties

	Type	Description	Required
translation	`number` `[3]`	Relative translation in processing CRS units	✓ Yes
rotation_angles_deg	`number` `[3]`	Euler angles in degree (see convention here)	✓ Yes
extensions	`object`	JSON object with extension-specific objects. Extensions follow the naming convention VENDOR[_(team❘product)]_extname	No

Calibrated sensor¶

Calibrated sensor Properties

	Type	Description	Required
id	`integer`	Unique ID of the sensor, it must appear in the input cameras.	✓ Yes
internals	`sensor_internals`	Calibrated sensor internal parameters.	✓ Yes
rig_relatives	`calibrated_rig_relatives`	Calibrated rig relatives contain the optimised relative translations and rotations in processing CRS units.	No
extensions	`object`	JSON object with extension-specific objects. Extensions follow the naming convention VENDOR[_(team❘product)]_extname	No

Fisheye internals¶

Parameters of the fisheye camera model as described in Pix4D knowledge base.

Fisheye internals Properties

	Type	Description	Required
type	`string`	Must be `"fisheye"`.	✓ Yes
principal_point_px	`principal_point`	(x, y) location of the principal point in pixels with (0, 0) being at the top left corner of the top left pixel.	✓ Yes
is_symmetric_affine	`boolean`	If true, it is prior knowledge that the affine matrix is symmetric (that is, c=f and d=e=0) and should be kept symmetric.	✓ Yes
affine	`number` `[4]`	Affine transformation parameters as [ c d; e f ]	✓ Yes
polynomial	`number` `[]`	The coefficients of the distortion polynomial.	✓ Yes
is_p0_zero	`boolean`	If true, it is prior knowledge that the first polynomial coefficient is equal to zero and should be kept zero.	✓ Yes
extensions	`object`	JSON object with extension-specific objects. Extensions follow the naming convention VENDOR[_(team❘product)]_extname	No

Internals¶

One of perspective, fisheye or spherical internal. Parameters of the camera models are described in Pix4D knowledge base.

Perspective internals¶

Parameters of the perspective camera model as described in Pix4D knowledge base.

Perspective internals Properties

	Type	Description	Required
type	`string`	Must be `"perspective"`.	✓ Yes
principal_point_px	`principal_point`	(x, y) location of the principal point in pixels with (0, 0) being at the top left corner of the top left pixel.	✓ Yes
focal_length_px	`number`	Focal length in pixels.	✓ Yes
radial_distortion	`number` `[3]`	The radial distortion coefficients (R1, R2, R3).	✓ Yes
tangential_distortion	`number` `[2]`	The tangential distortion coefficients (T1, T2).	✓ Yes
extensions	`object`	JSON object with extension-specific objects. Extensions follow the naming convention VENDOR[_(team❘product)]_extname	No

Principal point¶

(x, y) location of the principal point in pixels with (0, 0) being at the top left corner of the top left pixel.

Spherical internals¶

Spherical internals Properties

	Type	Description	Required
type	`string`	Must be `"spherical"`.	✓ Yes
principal_point_px	`principal_point`	(x, y) location of the principal point in pixels with (0, 0) being at the top left corner of the top left pixel.	✓ Yes
extensions	`object`	JSON object with extension-specific objects. Extensions follow the naming convention VENDOR[_(team❘product)]_extname	No

Example¶

{
    "format": "application/opf-calibrated-cameras+json",
    "version": "1.0",
    "cameras": [
        {
            "id": 47292894,
            "orientation_deg": [
                3.3432,
                -5.2849554,
                9.345113
            ],
            "position": [
                483.054,
                13.957,
                28.12
            ],
            "sensor_id": 18493134
        },
        {
            "id": 57282923,
            "orientation_deg": [
                2.35224,
                -4.4422,
                9.03452
            ],
            "position": [
                483.04,
                13.972,
                28.12
            ],
            "sensor_id": 21845677
        },
        {
            "id": 28493939,
            "orientation_deg": [
                1.4753,
                10.5839,
                -2.94832
            ],
            "position": [
                243.054,
                521.957,
                31.12
            ],
            "sensor_id": 57282113
        }
    ],
    "sensors": [
        {
            "id": 18493134,
            "internals": {
                "affine": [
                    1676.296432,
                    0.0,
                    0.0,
                    1676.296432
                ],
                "is_p0_zero": true,
                "is_symmetric_affine": true,
                "polynomial": [
                    0.0,
                    1.0,
                    0.0152646,
                    -0.161096
                ],
                "principal_point_px": [
                    634.45,
                    481.23
                ],
                "type": "fisheye"
            }
        },
        {
            "id": 21845677,
            "internals": {
                "affine": [
                    1637.34211,
                    0.0,
                    0.0,
                    1637.34211
                ],
                "is_p0_zero": true,
                "is_symmetric_affine": true,
                "polynomial": [
                    0.0,
                    1.0,
                    0.0152646,
                    -0.161096
                ],
                "principal_point_px": [
                    641.12,
                    479.65
                ],
                "type": "fisheye"
            },
            "rig_relatives": {
                "rotation_angles_deg": [
                    -0.456,
                    1.027483,
                    0.39229
                ],
                "translation": [
                    -0.015,
                    0.015,
                    0.0
                ]
            }
        },
        {
            "id": 57282113,
            "internals": {
                "principal_point_px": [
                    3001.23,
                    2011.2434
                ],
                "focal_length_px": 5312.353,
                "radial_distortion": [
                    -0.01444223,
                    0.012321123,
                    -2.13311e-05
                ],
                "tangential_distortion": [
                    0.001239402,
                    0.000432234
                ],
                "type": "perspective"
            }
        }
    ]
}