Calibration Panels and Co-Viewing in TV

I hear this term calibration panels come up a lot. And I mean, I guess to one hand, it could be a way to sort of make inferences about co-viewing by matching bigger panels with big data. But what do you think is the place for calibration panels and does co- viewing have any place in that conversation at all? It's funny because I would say I wouldn't even if it's a calibration panel, it's being used to affect it’s being used to supposedly inform the accuracy of a measurement.