The precise width of the canals is not determinable, although certain comparative measurements made by Prof. Lowell lead him to the conclusion that 15 to 20 miles is the width of the larger of the Martian canals, and 2 or 3 miles that of the more diminutive. (scientificamerican.com)
Gurche infers the size and shape of soft tissues in the face from skull dimensions and estimated body weight, using comparative measurements gleaned from the decades he has spent dissecting humans and ape species. (discovermagazine.com)
For scientific purposes, the Antarctic ice sheet is often divided into catchment basins so that comparative measurements can be taken to work out how the ice in each basin is changing and discharging ice to the oceans. (sciencedaily.com)