The method theoretically divides the tree stem into a number of (mostly) standard length sections. All the sections except the tip are assumed to be second degree paraboloids. The tip is assumed to be a cone. Volumes for these assumed shapes are easily calculated from simple measurements of diameter and length. The method is:

• suitable for both excurrent and deliquescent species
• practicable for felled and standing trees
• suitable for estimating total volume or volume to any merchantable limit, over or under bark
• involves reasonably simple calculations easily programmed for the computer.

Australian procedure

• Prior to metrication, Australian procedure was based on 10-foot sections, plus an odd log to 4" DUB (merchantable limit), and a tip. A comparable metric procedure involves 3 m sections and a top DUB of 10 cm.
  Note: The method can be based on sections of any constant convenient length.
• Measure diameter at the centre of each standard section and at the centre of the odd log. Also measure the length of the odd log.
• Calculate volume of each section by Huber's formula.
• Measure the length of the tip section.
• Calculate the volume of the tip, assuming it is a cone with a base diameter of 4" DUB (or other specified merchantable limit)

Practical aspects

• The first section may start at an arbitrary stump height but it is common to start from ground level and make a stump allowance in calculating merchantable volume.
• The tips of excurrent trees most closely approximate conoids. The point of inflection from the 2nd degree paraboloid to conoid shape is accepted as occurring at the 10 cm (4") DUB point.
• Normally, a section of stem < 3 m long (the odd log) will occur immediately below the merchantable height (unless merchantable height is an exact multiple of the constant section length).
• NOTE: The volume of the odd log must be based on a diameter measurement at its mid-length.

Bias of method

The volume estimate is unbiased to the extent that:

• each 3 m section and the odd log is a frustum of a 2 paraboloid
• the tip is conoid
• each nominated point of measurement is representative of the section.

Due to butswell, the butt section is mostly neiloid, so there is a possibility of bias in the butt log. The extent of bias (negative) depends on the flare of the butt and the height of the point of inflection above ground. This bias can be reduced by taking two 1.5 m sections in the butt section (measuring at 0.75 m and 2.25 m), but this is not common practice.

Precision of method

Positions of measurement on the stem are fixed so the method should be precise for the same operator and between operators.

However, unrepresentative points of measurement may reduce the precision between operators. Standard procedures for measurement at unrepresentative points are necessary to overcome this problem.

Detection of errors

The method does not allow any simple visual check on measurements, therefore one must be alert for:

1. mistakes in measurement,
2. conversion errors (diameter to sectional area),
3. recording errors,
4. arithmetic errors.

Mistakes in measurement can often be detected by a check to see that DOB, DUB and 2BT decrease with height in a sensible manner.

As most processing of stem measurements is now done by computer, nothing is gained by keeping section length constant (which aims at simplifying manual calculation rather than adequately assessing tree volume). Hence use of the Standard Sectional Method is declining in favour of the Taper Step Method of estimating stem volume which allows freedom in choosing representative points of measurement - one can ensure that they are biologically worthwhile and measurably consistent.

Note: The South Australian Regional Volume Tables and Yield Regulation Tables (Bulletins 20 and 23) were based on volumes derived by the Standard Sectional Method.

Other measurement techniques.