Module Outputs

Requirements	Software operation	Defining Calibration Tasks	Definitions and Theory
Supported Systems Supported Targets Required Evidence Test Setup	Calibration Procedure User Interface Use in Imatest IT Module settings Module outputs	Defining a Device Defining Distortion Defining the System of Devices Defining the Target Defining a Test Capture Defining a Test Image	Homogenous Coordinates Projective Camera Model Multi-Camera Systems Distortion Models Coordinate Systems Rotations and Translations

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Standard output from the Geometric Calibrator, either from Imatest Master or Imatest IT, comes in the form of a JSON-encoded structure.

This structure has the general structure, with objects in bold and arrays indicated by square brackets:

Top-level object
        <info about module run>
        devices [
               <info about device>
               intrinsics
               cam_to_cam
               ]

        captures [
               relative_to_target_origin
               images [
                      <info about image file, image points>
                       ]

               ]

 

JSON Output Description

 

Top level Object
Field	Data Type	Description
Timestamp	String	Date time string of when the calibration was run
Version	String	Imatest version number
Build	String	Imatest build
Runtime	Number
reference_device	String	UUID of the reference device
distanceUnits	String	Distance units
devices	Object or Array of Objects	Description of each device
captures	Object or Array of Object	Description of the test capture positions
coordinate_settings	Object	A description of the camera settings

 

devices sub-Objects (array)
Field	Data Type	Description
uuid	String	Unique identifier of device
name	String	User-provided name of device
serialNumber	String	User-provided serial number of device
sensorSize	Array	Number of pixels in the array [xSize, ySize]
pixelPitch	Number	The pixel pitch of the sensor
pixelPitchUnits	String	The units of the pixel pitch
intrinsics	Object	The intrinsic properties of the device
cam_to_cam	Object	The position of the device relative to the reference device
distortion_fit	Object	The distortion optimization results

 

intrinsics sub-Object
Field	Data Type	Description
f	Number	The focal length of the device
f_units	String	The units of the focal length
pp	Array of Numbers	The principle point of the device [PPx, PPy]
skew	Number	The skew of the device
alpha	Number	The focal length ratio of the device
distortion	Object	The distortion of the device

 

distortion sub-Object
Field	Data Type	Description
type	String	The distortion model type: rad_div_poly_packed
form	String	The polynomial form: All, Even, Odd
coeffs	Array of Numbers	The distortion coefficients [K1, K2, …]
center	Array of Numbers	The center of distortion [CODx, CODy]

 

cam_to_cam sub-Object
Field	Data Type	Description
direction	String
R	Array of Array of Numbers	The rotation matrix [[r11, r12, r13], [r21, r22, r23], [r31, r32, r33]]
coeffs	Array of Numbers	The translation to the reference device [tx, ty, tz]
center	String	The units of the translation

 

distortion_fit sub-Object
Field	Data Type	Description
opt_converged	Boolean	Indication if the optimization converged
nIters	Array of Array of Numbers	Number of iterations for the optimization
num_points	Array of Numbers	Number of image points used in the optimization
max_radius_used	Number	Maximum (distorted) radius used in the optimization
fit_mean_err	Number

 

Captures sub-Object (array)
Field	Data Type	Description
uuid	String	Unique identifier for the test capture
relative_to_target_origin	Object	Rotation and translation to the origin of the target
images	Object or Array of Objects	Description of the images used for calibration at this test position

 

relative_to_target_origin sub-Object
Field	Data Type	Description
R	Array of Array of Numbers	The rotation matrix [[r11, r12, r13], [r21, r22, r23], [r31, r32, r33]]
coeffs	Array of Numbers	The translation to the reference device [tx, ty, tz]
center	String	The units of the translation

 

images sub-Object
Field	Data Type	Description
filename	String	The filename of the image
uuid	String	The unique identifier of the image
device_uuid	String	The unique identifier of the device that captured the image
reprojection_err_norm_stats	Object	The reprojection stats for the image
detectedPoints	Array of Array of Numbers	The detected saddle points in the image [[x1, x2, …], [y1, y2, …]]
reprojectedPoints	Array of Array of Numbers	The reprojected points that correspond to the detected points [[x1, x2, …], [y1, y2, …]]
worldPoints	Array of Array of Numbers	The corresponding world (target) points [[X1, X2, …], [Y1, Y2, …], [Z1, Z2, …]]

 

reprojection_err_norm_stats sub-Object
Field	Data Type	Description
min	Number	The minimum reprojection error
mean	Number	The mean reprojection error
max	Number	The maximum reprojection error
percentile_95	Number	The 95th percentile of the reprojection error

 

coordinate_settings sub-Object
Field	Data Type	Description
count_from_one	Number	0 if array indexing begins at 0, 1 if array indexing begins at 1
origin_loc	String	Origin of the array: ul (upper left), ur (upper right), ll (lower left), lr (lower right)
flip_world_axis	Array of Numbers	Array signifying flipped (from right-handed) world coordinate system in each axis [X, Y, Z]. 0 is not flipped, 1 is flipped.
flip_image_axis	Array of Numbers	Array signifying the flipped image coordinates [x, y] from positive downward and rightward. 0 is not flipped, 1 is flipped.