To determine the length of an object, the image is first segmented (binarized). This means that the object must be separated from the background. The length measurement can then be carried out between any two points within the object. As with area measurement, calibration is required in order to be able to assign the number of measured pixels to a metric unit. Often the length of plant parts, such as roots or fibers, is measured, but this measurement can also be used in the calibration of components.