I was going to suggest that as well. An inverted 5-gallon bucket like the orange ones that can be purchased inexpensively at Home Depot are just the right height to set the caliper on. [assumes front axle is on jack stands]
Special tools? Yes, you will need a 12-point* metric socket for the four hub/bearing assembly bolts inside the knuckle.
* A 6-point socket will not work as the fasteners are 12-point cap screws.
Also, a puller will probably be required to remove the hub/bearing assembly from the front axle splines. A liberal dose of a quality penetrating oil ahead of time on the splines (after removal of the axle nut) should aid in removal.
I'm assuming you don't have a factory service manual. I would highly suggest you purchase or borrow one prior to embarking on a project such as this... I only covered several of the facets of the rotor R&R.