CRVAL
CRVAL, short for "Coordinate Reference Value," is a term used primarily in astronomy and astrophysics to describe the specific coordinate value at a designated reference point within a coordinate system or a dataset. It is a fundamental parameter in the World Coordinate System (WCS), which entails the transformation between pixel coordinates in digital images and real-world celestial coordinates.
In the context of FITS (Flexible Image Transport System) files, commonly used for storing astronomical data,
CRVAL works in conjunction with other WCS keywords, such as CRPIX (the reference pixel position), CD or
Variations of CRVAL can include CRVAL1, CRVAL2, etc., corresponding to different axes in multi-dimensional datasets. Proper
Overall, CRVAL plays a vital role in ensuring that astronomical data can be accurately linked to real