### The Correction of the Reference Length for the Selected Parts' Center  
We calculate the dimension of the reference length, \(RL_{distance}\), that results from the correction of the dimension \(RL\)\({}_{photo}\) by the dimension change caused by the non-zero distance of the perpendicular plane of the projection of a point \(\mathrm{S_{n,n+1}}\) (on the axis of the objective) from the \(RL\)\({}_{photo}\) position (Figure 9). The experiment has revealed (valid for the KYOCERA FINECAM M410R only) that, based on a selective correlation coefficient, we can consider the dependency \(RL_{distance}\) from the distance \(k_{distance}\) as linear, and hence the regression axis can be used to formulate the relationship as follows:  
\[RL_{distance}=a\cdot k_{distance}+b[\mathrm{mm}] \tag{2}\]  
where:  
Figure 8: Graphical representation of reference points (RPs) (source: The authors of this article). \(a=-0.74855714285\);  
\(b=+35.8198095238\). We have calculated the dimension of the reference length, \(RL_{hor}\) that originates from a correction of the \(RL_{distance}\) dimension of the objective defect in the view caused by a horizontal shift of the object from the center of the objective by the distance \(k_{hor}\) (Figure 10). Figure 10: Correction of the reference length in the horizontal direction (source: The authors of this article). Figure 9: Correction of reference length in the distance (source: The authors of this article). Calculation of the correction of the reference length in the horizontal direction is as follows:  
\[RL_{hor}=c_{hor}.RL_{distance}[\text{mm}] \tag{3}\] \[c_{hor}=f(k_{hor})\]  
Table 1 presents the values of the coefficient \(c_{hor}\) achieved in experiments (camera KYOCERA FINECAM M410R), by which we calculated the dimension \(RL_{hor}\) that originates from a horizontal movement \(RL_{distance}\) from the center of the photomontage increased by the distance \(k_{hor}\). Intervals (columns) are provided in the following tables. For the distance \(k_{hor}\), Table 1 defines the quotient \(k_{hor}\) as half of the horizontal dimension of the photomontage. We have calculated the dimension of the reference length \(RL_{vert}\), which is caused by the correction of the dimension \(RL_{hor}\) by the lens error in the display due to the vertical displacement of the object from the center of the lens by the distance \(k_{vert}\). The correction of the reference length in the vertical direction can be calculated as follows:  
\[RL_{vert}=c_{vert}.RL_{hor}\ [\text{mm}] \tag{4}\] \[c_{vert}=f(k_{vert})\]  
Table 2 shows the experimentally achieved values of the coefficient \(c_{vert}\) (camera KYOCERA FINECAM M410R), by which we can calculate the dimension \(RL_{vert}\) that originates from a horizontal movement of \(RL_{hor}\) from the center of the photomontage increased by the distance \(k_{vert}\). Indexes (columns) for the distance \(k_{vert}\) are reported in Table 2, which indicate a quotient \(k_{vert}\) as half of the vertical photomontage dimension. We have calculated the dimension of the reference length \(RL_{un,un,un}\), which originates from the correction of the dimension \(RL_{vert}\) after its rotation to the perpendicular axis (Figure 11). Angle \(\beta\) can be located from a tripod scale using an incline objective axis from the basic scheme for scanning of the reference length (Figure 5) in the basic scheme for the measurement of the vertical parachute speed using the photo-optic method (Figure 6). Angle \(\beta\) can be also determined by calculation.