**1. Introduction**

102 Advanced Topics in Measurements

Takeda M, Ina H, Kobayashi S (1982) *Fourier-transform method of fringe-pattern analysis for* 

The roundwood volume is one of basic parameters at its sale and purchase being indispensable operational information of every saw mill. The tree stem or its part (log) is an irregular body the form and volume of which can be determined by simple operational procedures only approximately. According to possibilities of measurement (conditions, equipment, time consumption etc.), methods of calculation and approach to problems more procedures have been proposed to determine the volume of roundwood. Many of these methods and procedures are used today. In Central Europe, Huber method became most widespread for manual measurements in the forest. The method compares the tree stem to a cylinder. The main advantage of this method consists in the low demands of measurements (diameter – 2 times perpendicular at each other under bark /u.b./ in the centre of the log length, diameter and length accurate to whole centimetres), easy practicability, no special equipment and sufficient accuracy.

Lines in log yards of present processing plants are ordinarily equipped with optoelectronic sensors and control systems evaluating virtually continuously the roundwood diameter (by at least 10 cm length) accurate to ±1 to ±2 mm and length accurate to ±1 cm. Also at the electronic measurement and calculation of the log volume on the basis of electronic measurements more procedures are used. Due to results in the determination of a mid diameter or volume electronic procedures are not even consistent with manual methods or with each other and their results do not correspond even to the geometric volume of logs. Different results of measurements are often the reason of doubts about the accuracy (rightness) of measurements reflecting also relationships between suppliers and processors of wood.

The aim of the presented paper is the description and analysis of currently used principles of sensing and evaluating the roundwood volume in Central Europe as well as quantification of deviations, which originate due to the use of various method of the determination of roundwood volume at the simultaneous determination of deviations on basic parameters of roundwood (diameter and length). Thus, the paper outlines possibilities to compare results determined according to different procedures.

The paper tries to describe comprehensively problems of sensing and evaluating the roundwood dimensions in order mutual relations to be obvious. In the descriptive part, it deals with methods of sensing the log diameter and length, which are used in Central Europe today. The paper mentions also main rules and regulations, which are related to the

 The log length – according to the length, the following processing the stem is determined. It also serves for classification and calculation of the volume of logs for

The log diameter in the length centre - it serves for the approximate log volume

 Log diameter at its top end – it is decisive for the way of log processing, serves for the subsequent classification of logs. For the volume calculation it can serve in cases when the log centre is not available, e.g. at log yards. However, results obtained in this way

Log diameter at its butt end – it is decisive from the aspect of the line passage (clearance

 A diameter continuously along the whole log length – it is necessary for subsequent processing – cross-cutting. The result of measurement consists in the suitable place of cross-cutting (necessary length and top end diameter), removal of defects, and the

Dimensions and volumes of particular stems (logs) have to be known already in place of felling, at the latest in places of skidding before the wood haulage from forest (cut records, output of workers and their remuneration). If felling is carried out manually by one-man chain saws then means used for measurements are usually simplest, namely a calliper and tape.

*Manual measurement* and its unpretending equipment is quite satisfactory from the aspect of the accuracy of its results (units – cm) and possibilities to carry out subsequent cross-cutting tree-length logs. Values of diameter and length create, at the same time, basic data for records and calculations of volumes. It is usually determined according to tables. Thus, the

At the measurement of particular logs we need to obtain following data:

calculation (at the majority of methods /not exclusively/).

production and commercial purposes.

are less accurate.

highest yield.

of subsequent machines)

Fig. 1. Electronic calliper with a tape.

measurement and reception of timber. It stems from the author's survey of using sensing and evaluation systems in the Czech Republic and literature data on these problems in surrounding countries (mainly Austria, Germany and Slovakia).

In the analytical and result part, a general algorithm is derived of processing sensed data. Steps are determined leading to different results of particular regulations. The results are compared with results of a method, which tries to evaluate the volume of logs (closest to the geometrical volume) from data taken by systems used at present. In relation to the volume determined in this way properties of existing procedures are also mentioned.

At the end, the paper indicates directions for the further progress of research and agreements as well as legislative regulations with a view to minimize differences in the measurement and determination of the volume of roundwood.
