"Ground truth" refers to the most accurate and reliable information available. It represents the real, undeniable facts or circumstances about a particular situation or problem. Full definition
«Understanding the impact of these storms will help us gain ground truth for improving the chemistry — climate models we use to project future climate,» she says. (scientificamerican.com)
The images and text / oral descriptions of each cloud type by altitude will allow students to more accurately collect ground truth data. (nasawavelength.org)
The story has another twist that also underscores the importance of checking orbital data against ground truth. (sciencedaily.com)