Is there any altimeter access available through the browser? Would be neat to use this in 3D, could be done with a native app but I don't think in the browser.
Do you have more information about what exactly you would like to achieve?
The barometers available on devices would allow this to happen, but I don't know (don't think) that when you request location access via the browser it returns altitude information if the device supports it.
Moreover, measuring the volume would require tracing out a much more complicated path since volumes are bounded by surfaces rather than edges. Given that the technical problems were solved, do you think that a human actually could manage to trace out a volume in an other cases than simple rectangular blocks etc?