CD15 virtual tracking head is the supporting equipment for virtual tracking system. It is not only has the basic functions of ordinary fluid head but is also equipped with high-precision absolute angle sensors inside the head. The sensors have a precision of 19 bits and an angle resolution of 0.0007°. The absolute value sensors do not require repositioning upon startup, and maintain the original position data after a power loss, eliminating cumulative errors and making them more convenient and reliable to use. The head uses a more precise bubble level than ordinary head to prevent data drift.