Volume base surfaces

A volume is the gap between the captured surface and a base that you assume. The base changes the answer without changing the concrete, so it is recorded with the finding and printed with the figure. Select it in Against, in the Measurement panel. To compare the bases in diagrams, click ? beside the volume.

Base surfaces you choose

No.	Base surface	The base is	Use it when
01	Triangulated (oriented) — the default	A surface stretched over all your points, following every one of them. The only base that is not flat	You can see the edges of the volume all the way round and the surface is fairly even
02	Flat average (oriented)	One flat sheet through the average of your points. It can tilt to match a slope	You can see the edges all the way round and the surface is fairly even
03	Flat custom (horizontal)	One level sheet at a height you enter in Altitude (m)	You already know the level — a spillway crest, a design level
04	Flat lowest (horizontal)	One level sheet at the height of your lowest point	Measuring what sits on a floor — a stockpile, a deposit against a wall
05	Flat average (horizontal)	One level sheet at the average height of your points	You can see the edges all the way round and a level base suits it
06	Flat highest (horizontal)	One level sheet at the height of your highest point	Measuring what is missing from a hollow — a pit, a scour hole

“Oriented” bases can tilt with your points; “horizontal” bases are level whatever your points do.

References AerTwin chooses for you

Reference	Used by	What it is
Defect — missing concrete	3D defect	Fitted to the sound concrete just outside your outline. You do not choose it, and it works on a vertical wall
The plane through your own points	Volume, when the outline is on a face	The tool switches to this when your outline is on a near-vertical face. Its rows read proud and recessed, never cut and fill
The straight line between your two picks	Depth profile	Nothing is fitted; every figure is measured square to the line

Important

To measure concrete missing from a sound face, use 3D defect, not Volume. A ground-based volume on a wall measures the wrong thing; the 3D defect tool measures square to the face it fits.