I wouldn't say that measurement itself is an illusion. Due to Earth's gravitational pull, it directly effects the expansion of objects. It was recorded on March 2016, an astronomer Scott Kelly, grew 3 inches in space due to the lack of a gravitational pull. I would rather phrase that measurements is dependent on our external conditions, for example we have a basic unit system so that despite or own perspective we human can globally interpret our external conditions. Therefore, if our conditions changed like a different planet than we would have to change our basic measurement system.