# Calibrate Functions

Calibration is the process of converting pixel measurements into meaningful, real-world values. In this process, a two-dimensional (2D) transformation mathematically maps points from pixel coordinates of an image to real-world coordinates. Once an image has been calibrated, other vision tools can then reference the calibration as an input, and report the results in the calibrated (real-world) units.

Note:

- When using a Calibrate function, the physical and optical set-up (the lens, sensor and the physical relationship between the sensor and the scene being acquired) must be the same for both the calibration and run-time operation. If any of these items is altered, the system must be re-calibrated. Therefore, it is recommended that the same sensor and lens be used to both calibrate and process the run-time images. The sensor and lens must also retain their original set-up and calibration settings. For example, changing the acquisition format (by altering the resolution) or moving the sensor invalidates the computed 2D transformation that maps pixel to real-world coordinates.
- The output of any vision tool that reports in real-world coordinates cannot be used as a fixture or region input to another vision tool.