On 'ground' truth and why we should abandon the term

I make a case to abandon the use of the term "ground truth." After a brief history of the term that indicates its military origins, two main arguments are presented against the use of the term. The first is from measurement theory. The second is by way of presenting three examples: the first is in crop mapping, in which "ground truth" may have some validity. This is presented as the exception to prove the rule. The second example looks at albedo, in which the measurand is the same for the local and remote measurements, and evidence is provided to support this paper's argument. The third example looks at the scattering phase center in radar. In this case, the measurand is different for the local and remote measurements, and an argument is given for why this does not warrant the use of the term. Finally, a heuristic checklist that seeks to guide readers to reflect on whether or not their particular field measurements should be referred to as "ground truth" is provided. (C) 2021 Society of Photo-Optical Instrumentation Engineers (SPIE)