Specifications of xmp.camera tags

Projects which require radiometric calculations (e.g. agriculture applications): Refer to the camera XMP section as well as this page which gives the specifications for the different corrections to be applied: Camera radiometric correction specifications.

(XMP) Camera

Key Value example Type Meaning
Xmp.Camera.ModelType "fisheye" Ascii Camera model type: one of "perspective" or "fisheye".
Xmp.Camera.PrincipalPoint 2.42299,1.850154 Ascii cx, cy in millimetres separated by comma.
Xmp.Camera.PerspectiveFocalLength 4.569165 double For perspective camera: focal length in millimetres.
Xmp.Camera.PerspectiveDistortion

0.201690322,-0.358534038,

0.256185599,

0.004208643,0.000268361

Ascii For perspective camera: R1, R2, R3, T1, T2 separated by comma: How are the Internal and External Camera Parameters defined?.
Xmp.Camera.FisheyeAffineMatrix

1583.319083002,0,0,

1583.319083002

Ascii For fisheye camera: Affine matrix C, D, E, F separated by comma: How are the Internal and External Camera Parameters defined?.
Xmp.Camera.FisheyeAffineSymmetric 1 Boolean For fisheye camera: If symmetric affine matrix should be used (default false).
Xmp.Camera.FisheyePolynomial

0,1,-0.025178575,

0.167834214

Ascii For fisheye camera: Polynomial separated by comma: How are the Internal and External Camera Parameters defined?.
Xmp.Camera.RigName Airinov multiSPEC4C 1.1 XmpText Name of the rig model this image belongs to.
Xmp.Camera.RigCameraIndex 0 Short Corresponding camera index within the rig model.
Xmp.Camera.RigRelatives 0.3836, -1.27665, -0.1156 XmpText Rotation angles with respect to the reference camera. For angle convention in Pix4D: How are defined omega, phi, kappa?.

(XMP) Radiometric correction

Key Value example Type Meaning
Xmp.Camera.BandName {"Red", "NIR"} XmpSeq

Name of each band (sequence).

Single page image: one name for each band of the image.
Multipage image: one band name per image page. (Note: this allows only one band per page since the sequence of the sequence is not possible).

The band name must not start with the following characters: 0-9, ',', '(' or ')'.

Xmp.Camera.CentralWavelength {660, 800} XmpSeq Central wavelength of each band in nm. Similar to band names. If band names are not defined, default band names are generated.
Xmp.Camera.WavelengthFWHM {10, 10} XmpSeq Full-width half maximum of the wavelength distribution in nm.
Xmp.Camera.BlackCurrent

{10, 7}

XmpSeq Dark current for each band/page: Camera radiometric correction specifications.
Xmp.Camera.BandSensitivity {0.78, 0.043} XmpSeq The sensitivity of each band (pixel intensity value per irradiance).
Xmp.Camera.SunSensor {12.87, 9.72} XmpSeq Sun irradiance sensor (upwards looking sensor) raw value for each band.
Xmp.Camera.SunSensorExposureTime {0.1, 0.1} XmpSeq Sun irradiance sensor exposure time in seconds.
Xmp.Camera.SunSensorSensitivity {16.45, 14.08} XmpSeq Sun irradiance sensor sensitivity.
Xmp.Camera.InvalidPixel {"40,593,981,291"} XmpSeq List of bad pixels as comma-separated x,y coordinate list, one sequence for each band.
Xmp.Camera.VignettingPolynomial {"0.00325, 1.983e-6, 5.0983e-9"} XmpSeq Vignetting correction by radial polynomial: 1D polynomial coefficients (one string of comma-separated values per page, 1 string for RGB images): Camera radiometric correction specifications.
Xmp.Camera.VignettingCenter {"542,912"} XmpSeq Vignetting correction by radial polynomial: Center point cx, cy in pixel (one string of comma-separated values per page): Camera radiometric correction specifications.
Xmp.Camera.VignettingPolynomial2DName {"0,0,1,0, ..., 2,2,3,1"} XmpSeq Vignetting correction by 2D polynomial: name of coefficients: n,m for c_{n,m} separated by commas (one string of comma-separated values per page): Camera radiometric correction specifications.
Xmp.Camera.VignettingPolynomial2D {"0.633287676149, 1.47936368033, ..., -1.58329242609, 0.130259802058"} XmpSeq Vignetting correction by 2D polynomial: coefficients c_{n,m} for names given by Xmp.Camera.VignettingPolynomial2DName separated by commas (one string of comma-separated values per page): Camera radiometric correction specifications.
Xmp.Camera.ColorTransform

{1, -0.114886,-0.0456918,

-0.176716, 1, 0,

-0.0715561, 0, 1}

XmpSeq Sequence of double, color conversion matrix (for RGB: R2R, G2R, B2R, R2G, G2G, B2G, R2B, G2B, B2B). Considering the information as a 3x3 matrix M, (R,G,B)<sub>new</sub>= M * (R,G,B).
Xmp.Camera.IsNormalized 1 Bool Defines whether the radiometric correction is required (value 0) or the data has already been corrected (value 1) and therefore should not be corrected.

(XMP) Radiometric calibration target

Key Value example Type Meaning
Xmp.Camera.Albedo {0.22, 0.19 , 0.37} XmpSeq For radiometric calibration target images: Albedo of the disk for each band/page.
Xmp.Camera.ReflectArea {"X1,Y1,X2,Y2,X3,Y3,X4,Y4", "X1,Y1,...", ...} XmpSeq For radiometric calibration target images: polygon defining the target area for each page.
Xmp.Camera.CalibrationPicture 2 Short

Specifies if this image is a radiometric calibration target: 0 = no, 1 = yes but invalid, 2 = yes and valid.

For Sequoia cameras: 0 = no, 1 and 2 = yes.

(XMP) Position and orientation

Key Value example Type Meaning
Xmp.Camera.Yaw 72.7942 Rational or Double Orientation data in degrees. For more information on the definition of yaw, pitch, roll: How are defined yaw, pitch, roll?.
Xmp.Camera.Pitch 1.7943 Rational or Double Orientation data in degrees. For more information on the definition of yaw, pitch, roll: How are defined yaw, pitch, roll?.
Xmp.Camera.Roll 2.8909 Rational or Double Orientation data in degrees. For more information on the definition of yaw, pitch, roll: How are defined yaw, pitch, roll?.
Xmp.Camera.GPSXYAccuracy 5 Rational Horizontal GPS Accuracy in meters.
Xmp.Camera.GPSZAccuracy 10 Rational Vertical GPS Accuracy in meters.
Xmp.Camera.GyroRate 0.0487 Rational Gyro rate during image acquisition, lower = better quality.
Xmp.Camera.IMUPitchAccuracy 0.113 Rational The value in degrees of 1-sigma of the Gaussian noise of the IMU Pitch measurement.
Xmp.Camera.IMURollAccuracy 0.087  Rational The value in degrees of 1-sigma of the Gaussian noise of the IMU Roll measurement.
Xmp.Camera.IMUYawAccuracy 1.250  Rational The value in degrees of 1-sigma of the Gaussian noise of the IMU Yaw measurement.
Xmp.Camera.NominalCameraDistance 25.87 Rational Nominal GPS distance between calibrated cameras in meters in order to have a decent overlap. Use to dynamically remove the cameras with worst quality as determined by the GyroRate such the target distance is as specified.
Xmp.Camera.AboveGroundAltitude 25.3 Rational or Double Altitude above ground/take-off location in meters (from the altimeter of the drone).

(XMP) Sun irradiance position and orientation

Key Value example Type Meaning
Xmp.Camera.SunSensorYaw 72.7942 Rational or Double Sun irradiance sensor orientation data in degrees. For more information on the definition of yaw, pitch, roll: How are defined yaw, pitch, roll?.

Xmp.Camera.SunSensorPitch

1.7943 Rational or Double Sun irradiance sensor orientation data in degrees. For more information on the definition of yaw, pitch, roll: How are defined yaw, pitch, roll?.
Xmp.Camera.SunSensorRoll 2.8909 Rational or Double Sun irradiance sensor orientation data in degrees. For more information on the definition of yaw, pitch, roll: How are defined yaw, pitch, roll?.
Xmp.Camera.SunSensorRelativeRotation 175, 0, 0 XmpSeq Relative angle between camera and sunshine sensor in the omega, phi, kappa system (same as rig relatives).

(XMP) Bit-depth reduction

Key Value example Type Meaning
Xmp.Camera.TransformAlpha {55684.1, 58672.8, 58889.1} XmpSeq

Sequence of double, alpha parameter for each band.

This and the following two tags are used to undo a gamma transform which has been applied to fit data in 8bit space without losing the dynamic range:
pixel_final = alpha * pixel_normalized^gamma + beta;

where pixel_normalized is the pixel value stored in the JPG image scaled to the [0,1] interval.

Xmp.Camera.TransformBeta {9850.9, 6862.2, 6645.91} XmpSeq Sequence of double, beta parameter for each band.
Xmp.Camera.TransformGamma {2.12109, 2.6243, 2.33549} XmpSeq Sequence of double, gamma parameter for each band.

(XMP) Miscellaneous

Key Value example Type Meaning
Xmp.Camera.SensorBitDepth 14 Short Bit depth of the original sensor.
Xmp.Camera.SensorTemperature 43.4 Double Temperature of the sensor [degree Celsius].
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