Units of measurement, symbols, significant digits and rounding off
1.1 Units of measurement and symbols
1.2 Significant digits
1.3 Rounding off
1.4 Bias, accuracy and precision
Individual Trees and Logs
2.1 Bole characteristics
2.1.1 Diameter
2.1.2 Height
2.1.3 Bark thickness
2.1.4 Volume
2.1.5 Stem form and taper
2.2 Log characteristics
2.2.1 Diameter
2.2.2 Length
2.2.3 Volume
2.2.4 Weight
2.2.5 Allowance for defect
2.3 Crown characteristics
2.3.1 Width
2.3.2 Depth
2.3.3 Surface area
2.3.4 Volume
2.3.5 Biomass
2.4 Stem analysis
Groups of Trees (Stands)
3.1 Number of trees
3.2 Diameter
3.3 Basal area
3.3.1 Fixed-area plots
3.3.2 Angle count sampling
3.3.3 Advantages and disadvantages of angle count sampling
3.4 Height
3.4.1 Mean height
3.4.2 Predominant height, top height, dominant height
3.4.3 Stand height curve
3.5 Volume
3.6 Crown closure
3.7 Crown biomass
3.8 Growth and increment
References
Appendix 1: Checklist of equipment and materials
[RWG#2] [Copyright] [Title Page] [Next Page] [Last Page]
2.2.4 WEIGHT
Measurement of timber quantity by weight (weight scaling) has many attractive advantages when large quantities of material are involved for which it is fast, easy and objective. For smaller operations, or if weight scaling is not feasible, log dimensions must be measured and log volume tables applied to derive the volume.
Weight scaling is the most efficient method of assessing 'log volume' provided access to a weighbridge is practicable. Log volume is then derived from green (wet) weight using a conversion factor (CF) established by continuous sampling :
where V is volume (m3) and W is green weight (tonnes). The conversion factor will vary not only with region, species, tree age/size and the amount of bark on the logs, but also with the season and the time elapsed between felling and weighing.
Timber weight is recorded to the number of significant figures required, usually two or three. On trucks, it is usually measured by subtracting the empty weight (tare) of the truck from the loaded or gross weight. Because the tare is a constant and includes the weight of fuel, oil, water, and ancillary equipment (chains, bolsters, etc.), these must be the same at each weighing. The problem of a variable tare can be avoided if a weighbridge is available at the mill site. Then, each truck is weighed loaded and immediately after unloading, a practice now commonly applied in modern mills. Alternatively, the timber can be weighed as it is loaded in the forest using an electronic device such as a 'Loadrite' mounted on a front-end loader. The 'Loadrite' is a small transducer which uses the hydraulic pressure in the loader arms to weigh a bundle of logs. It can assess loads in the bush and accumulate the results over a series of lifts. Its capacity is 40 tonnes/lift and data can be accumulated to 2000 tonnes. It avoids the need for tare weights.