To evaluate the performance of proposed segmentation algorithm we compare output images with ground truth images. Ground truth images contains nothing but required segmentation. These are generated by using the free hand tool or ROI techniques.
Image annotation is the process by which a computer system automatically assigns metadata in the form of captioning or keywords to a digital image
The ground truth can be prepared by the field expert through the annotation process.
Initially, the expert can take the help of any software to make a basic region map preparation and the refinement can be done by the expert. It can also be verified by two or three experts (the group of experts) to make a standard for the ground truth of a particular dataset.
A definition also provided by Aparna Sathya Murthy