Don't worry: you won't have to go into the loft to measure the depth of the insulation.

The results capture the number of firms experiencing a fall in output but do not measure the depth of the fall.

Balloon-carried hygrometers give information on the humidity of the cirrus cloud but are not accurate enough to measure the depth of the cloud.

But, while such discontinuities may reveal the existence of chasms, they can never measure their depth.

Single-beam echosounders and fathometers began to enter service in the 1930s which used sonar to measure the depth beneath a vessel.