Geometric Calibration

Software Operation

Requirements Software operation Defining Calibration Tasks Definitions and Theory

Supported Systems

Supported Targets

Required Evidence

Test Setup

Calibration Procedure

Use in Imatest Master

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


 

The calibration procedure used by the Imatest Geometric Calibrator is a non-linear parameter estimation procedure. Understanding the nature of this calculation is useful for designing an appropriate test setup and knowing what options to set in the software, whichever interface you use. 

 

Software Interfaces

Imatest Master

Interactive GUI.

Create Calibration Tasks created in a series of menus, run the calibration procedure, and get data outputs as well as some visualizations.

Imatest IT

 

API for Python, C++, C, and .NET. 

Create calibration tasks programmatically and retrieve calibration data from a function call.

 

Geometric Calibrator produces the same calibration results (in JSON-data form) in Imatest Master and Imatest IT when supplied with the same Calibration Task and INI. Currently, Master provides some interactive visualizations of the results which IT does not. 

 

Module Inputs

Inputs are described by the Calibration Task. This includes the image files to be used (in the form of paths to the files on disk), the definition of the system, and the description of the test setup.

As in other Imatest modules, operational software parameters are defined in an INI file. This includes options about how to decode input images, how the module runs (e.g., whether or not it throws an error if the target cannot be detected in one image), and some optimization parameters.

Options are set interactively from the Settings window in Imatest Master. Imatest IT users may construct the relevant config file by hand or receive one from another source.

The relevant INI fields are found on the Module Settings page. 

 

Module Outputs

The basic output of the Geometric Calibrator is a JSON-encoded string with:

  • The calibration parameters of the input system (intrinsics and inter-device extrinsics)
  • Information about each Test Capture, including
    • The estimated pose 
    • The detected and reprojected points found in each image taken at that position
    • Information about the estimation convergence

The structure of these outputs is described on the Module Outputs page.