Pete Riegel somewhere wrote that calibrating on pavement and measuring on a trail was most likely to prevent a short course.
I did a direct comparison once: Pneumatic and airless tired bikes calibrated on pavement and then on a trail surface. Then measured a course with both bikes. Then recalibrated both on trail and pavement. Yes, it was a long day. I thought I could see a lot more particulate adherence to the tires in the early morning dampness than in the hot afternoon when the surface dried out. The airless tire recalibrated about the same. The pneumatic did expand but not as much on the trail as on pavement. Normally, the airless tire barely expands during a typical day's 20 F heat up. Based on that, I agree with Pete that a pavement calibration course is much more reliable / repeatable than a trail calibration course. If you don't want the trail or grass course to be long, wait till it is dry in the afternoon to measure.