**6. Possibilities of minimizing the differences**

At present, the accuracy of sensing and evaluating the log length ranges about ± 2 cm, diameter ±1mm, directions of the diameter measurement are usually 2 perpendicular at each other (at 2D sensing) up to 180 (i.e. at 1° angular rotation at 3D sensing), the diameter measurement density is between 1 and 10 cm log length.

For the purpose of wood processing the accuracy and details of taken and evaluated parameters of logs are quite sufficient. At trading with timber, an error occurring at the determination of dimensions or volume of logs is not a difficulty (problem), but differences in values of these quantities, which originate at using different methods of measurement (sensing and evaluating results obtained).

An ideal procedure to increase the accuracy of evaluating the log volume and to remove differences originating among particular procedures of measurements is to create and accept one technically unambiguous legislative rule (law, standard) obligatory for the electronic measurement of timber for the purpose of trading, and thus also electronic reception. However, expectations to create and mainly to accept such rules and regulations are not real at present both at a national and international level. To minimize effects of different rules it is necessary to start from following facts:


By its results, the procedure is comparable with the EN 1309 – 2 Standard. The higher value of the evaluated volume of logs according to the Ö-Norm L 1021 Standard by about 1% in the area of log diameters over 24 cm is caused mainly by removing the conversion of mm values of the mid diameter to whole cm not taking mm units into account. A fact that a difference obvious in the diagram is lower than a difference mentioned here causes the reduction of the log volume value at ÖN L 1021 placing the mid diameter measurement into the centre of a geometrical length and determination of the mid diameter as a lower but not

The advantage of the ÖN L 1021 Standard at the evaluation of the mm values of measurements consists in the even course of characteristics in the zone of log diameters below about 24 cm. Methods using "cutting off " mm units (although "only" once, such as EN 1309-2) show an appreciable decline in this area. However, no sawmill was found, which

At present, the accuracy of sensing and evaluating the log length ranges about ± 2 cm, diameter ±1mm, directions of the diameter measurement are usually 2 perpendicular at each other (at 2D sensing) up to 180 (i.e. at 1° angular rotation at 3D sensing), the diameter

For the purpose of wood processing the accuracy and details of taken and evaluated parameters of logs are quite sufficient. At trading with timber, an error occurring at the determination of dimensions or volume of logs is not a difficulty (problem), but differences in values of these quantities, which originate at using different methods of measurement

An ideal procedure to increase the accuracy of evaluating the log volume and to remove differences originating among particular procedures of measurements is to create and accept one technically unambiguous legislative rule (law, standard) obligatory for the electronic measurement of timber for the purpose of trading, and thus also electronic reception. However, expectations to create and mainly to accept such rules and regulations are not real at present both at a national and international level. To minimize effects of different rules it

 At present, the accuracy of log dimension measurements is not limited by accuracy or the density of sensing (accuracy ordinarily ± 1 mm, sensing frequency commonly in

 Accuracy of the evaluation of results is given by procedures derived from procedures for the manual measurement (determination of a mid diameter only from measurements carried out in the area of the log centre, determination of the log volume as the volume of one cylinder of a diameter equal to the log mid diameter and a length

 Regulations do not describe quite exactly all steps of processing the scanned data necessary at the electronic measurement. Thus, there is an area for the individual interpretation of the rules and affecting the results of measurements without the legislative disturbance of rules. It refers mainly to the filtration of scanned data (it is not

kHz) or possibilities of evaluating the results of measurement.

average value from measurements in both places of the measuring area.

would virtually use the given version of Ö-Norm L 1021.

measurement density is between 1 and 10 cm log length.

(sensing and evaluating results obtained).

is necessary to start from following facts:

equal to the log nominal length).

**6. Possibilities of minimizing the differences** 

defined at all) and directions where the mid diameter is evaluated. In some rules, these are determined only as "perpendicular at each other" and concrete directions are not specified.


If we suppose the use of more methods in the future, the value of the log volume (reached at the electronic measurement of timber) will correspond rather to commercial needs than to the geometrical volume. Thus, it is necessary to understand it as a "commercial volume". Following steps are derived to increase the stability of measurements (repeatability with the same or near results) by any method and to reduce deviations.

It is inevitable to determine unambiguously the method of assessment and implementation of particular steps of the algorithm of data processing. Without these conditions it is not possible to determine more exactly properties of the given procedure (regulations, standards). It represents:


It is suitable to determine the quality of roudwood where results of measurements are still valid. The worst quality of saw logs is supposed. At the worse quality of logs (sweep, stem curvature, knots, buttress) it is possible to suppose higher misrepresenting effects of data filtration and thus the decline of measurement accuracy.

Properties of used procedures (mainly dependences of the value of the calculated log volume) have to be determined with respect to a reference method. The comparison of two methods is suitable only for particular cases and cannot be used for the determination of actual properties of procedures. The volume of logs determined by a reference method has to approach geometrical volume. Comparison with a geometrical volume determined e.g. by a volumetric method (Hauffe, P. & Müller, L, 2002) is ideal however laborious, time

whole cm. Units of mm, which are included in electronically taken data, are not taken into account at the conversion. This "cutting off" is carried out even 2 times one after another in

The rate of decline of values of the log volume achieved according to particular procedures is compared with the volume of logs determined by a section method (sections as cylinders of a length of 10 cm and diameters given in mm). The method is selected because it evaluates (from given data on the log) a volume, which is closest to the log geometrical volume. The rate of decline varies from -5.5% (German Rahmenvereinbarung für die Werksvermessung von Stammholz, logs of medium diameters) to -9% (Austrian Ö-Norm L 1021, mid diameter value given in whole cm). Procedures, which give lower deviations (EN 1309-2 – 1.5 to 3%, ÖNorm L 1021, mm version – 0.7 to 3% or the ČSN 48 0050 Standard 48 0050 – 1 0.3 to 0.8%) are used minimally in practice (in the CR, their use was not found at all). Results achieved correspond to a comparison carried out in Germany (Sauter, U.,

The values are affected by the way of filtration of taken data. The filtration is a necessary step, which is carried out always. The method of its implementation is not, however, included in any known Central-European regulation. Through various types of filtration applied at the same taken data on logs even about 2% deviations (from values presented in

At the majority of procedures, the fall (deviation) is considerably dependent on the roundwood diameter. It is less dependent (but not insignificantly) on its length. In the paper, the dependences are presented in diagrams. Values of the roundwood/log volume obtained by one procedure cannot be therefore "converted" (with operational accuracy) to values obtained by another procedure using one universal coefficient. It is always necessary

From the operational aspect it is not necessary to know the volume of roundwood exactly. Present technically achievable accuracy is quite sufficient for timber processing. From commercial aspects, the actual deviation is not important but its various values at various

An ideal solution into the future is to unify procedures. However, experience from negotiations does not make possible the author to believe in the early realization of this solution, because the will of parties concerned is missing. Therefore, it is necessary to aim at: Exact defining all steps of sensing and processing the data of algorithms, the regulations to provide minimum space for "individual interpretation" and thus

 Definite determination of a method of the mutual comparison of results. In addition to the higher accuracy of comparison there is also the decline of commercial profitability

 The inspection and calibration of measuring equipment, which will involve and affect checking the implementation of all steps including the value of a resulting volume (at present, it does not include e.g. data filtration). Calibration should be worked out both

affecting results (at present e.g. 2D and 3D sensing but also filtration).

to take into account properties of the concrete delivery of roundwood.

the course of calculations, namely at basic measured values and at average values.

Staudenmaier, J. & Verhoff, S. 2010).

to use various procedures.

technically and legislatively.

the paper) were achieved.

procedures.

consuming and not practicable everywhere. A procedure of measuring the logs by sections appears to be sufficiently accurate and generally practicable. The length of sections derived from the minimum requirements of present regulations is 10 cm. In addition, the method accuracy is supported by the lower sensitiveness of the section method to the type of filtration. Misrepresenting effects of filtration become evident in the volume deviation of one section but not of the whole log (in a limiting case). Properties of particular procedures given in this paper are expressed in the same way.

To check and calibrate the equipment, procedures are proposed, which affect both accuracy of sensing geometric parameters of timber (logs) and the method of their evaluation. It is achieved by static sensing the etalons/measurement standards/ (the present method of the inspection of accuracy of setting the equipment and sensing the log dimensions) and subsequent operational (dynamic) measurement (checking the filtration and processing results of measurements). For calibration in this way it is necessary to determine (in rules, regulations) allowable tolerances of particular measurements and resulting evaluated values. It has not been determined for dynamic measurements yet.

The inspection of equipment is also related to the determination of authorities qualified to check and calibrate electronic measuring devices (existing in the majority of countries) and determination of sanctions at the infraction of agreed procedures of measurements and determination of geometrical parameters of logs (so far not existing in the Czech Republic). However, it refers to themes occurring out of the field of measuring systems.
