5m and 20m

10m and 15m

15m and 20m

20m and 30m

Gunter s chain

Revenue chain

Metric chain

Engineer s chain

What is the surface that is normal to the direction of gravity at all points?

Horizontal surface

Horizontal line

Level surface

Level line

Vertical line

Datum line

Horizontal line

+/- 3 mm

+/- 5 mm

+/- 6 mm

+/- 8 mm