What is the black and yellow circular icon on the nose of J 15 carrier aircraft?

This is an artificial symbol of industrial digital photogrammetry.

Digital Photogrammetry (Basic? Concept? Yes? Numbers? Photogrammetry is a photogrammetry based on the basic principles of digital image and photogrammetry, which uses the theories and methods of computer technology, digital image processing, image matching, pattern recognition and other disciplines to extract the geometric and physical information expressed by the photographed object in a digital way.

The symbol used on J-15 is J-15. When taking pictures of it during take-off and landing, these signs help to accurately locate the position to be measured.