some issues regarding the calibration of the terrestrial laser scanner leica scanstation c10.

by:Sinowon     2020-01-01
3D laser scanner on the ground (TLS)--
A new type of testing instrument-
Has become more and more popular and is increasingly used to provide-
Building and modeling data in various applications including land survey, archaeological research, construction, bridge structure and road survey.
These scanners can measure thousands of data points (
Distance, angle and reflection return signal power)
Generate a very detailed \"point cloud\" data set per second.
In addition, in most cases, these measurements are much faster than conventional geographic measurements;
Therefore, ground laser scanning has become an additional measurement technology in the past few years.
However, compared with the traditional land survey instruments (e. g.
Terminal, level of global navigation satellite system)
The accuracy and system error of most available laser scanners are not very goodknown.
For laser scanners for high-precision applications, investigation and analysis are essential (e. g.
Engineering measurement).
In order to minimize the system impact of the instrument error, the scanner must be calibrated and based on the calibration parameters (Ingensand 2006).
There is a standardized calibration procedure for traditional earth survey and photographic measuring instruments.
In the context of tls, since the construction of the laser scanner is completely different from that of traditional measuring equipment, reliable accuracy evaluation is quite complex. (
Briese 2007, Pfeifer).
The precision specifications given by laser scanner manufacturers in their publications and brochures are not comparable.
Experience has shown that given precision parameters should not be trusted in some cases;
In addition, the accuracy of these instruments-
Built in smallseries-
The instrument is different depending on the individual calibration.
A lot of work has been done at this point
Based on TLS calibration, use their similarity with the station or station (
Grun 2005, Parian;
Franhti, Franke 2005;
Lichti, Licht 2006; Lichti2007; Reshetyuk 2006). Self-
Some researchers have recently studied calibration methods that can be classified according to the target type.
It is reported that there are two types: Sign points and plane features.
The common ground between the two methods is to collect highly redundant spherical observation sets (
Range, horizontal direction and pitch angle)
Different locations in a powerful geometric configuration. (
Pei Yongjun, Lichti 2007; Dorninger, etc. 2008; Schneider 2009).
The application of the above program requires a laboratory or calibration room with known target or plane characteristic geometric parameters.
The calibration procedure mentioned uses the 3D coordinates of the measured point;
However, the range, vertical and horizontal angles, actually measured by the laser scanner (
Pfennigbauer, Ulrich 2010).
Therefore, it is important to evaluate each measurement parameter separately (Chow et al. 2010).
Some work has been done in distance measurement accuracy evaluation (Salo et al. 2008; Cheok et al. 2007)
Accuracy depends on many factors, such as scanner models, range measurement methods, target attributes, etc, as indicated below.
The accuracy test of angle measurement indicates the accuracy of angle measurement (
Verticalone in particular)
Depending on the design of the laser beam deflection unit (
Schwalbe 2008 Schneider;
Reshetyuk 2009, 2010).
It is important to note that there are no standard standards and evaluation methods for measuring the performance of electric fans (Lichti 2010).
The method proposed by the author of this paper allows the evaluation of distance and angle measurement accuracy under real environment conditions.
In addition, the method does not require a specialized Calibration Laboratory;
As a result, a standard Earth survey baseline can be used. 1.
The distance measurement device of the Terrestriallaser scanner calibration of the distance measurement device of the terrestriallaser scanner Leica Scanstation C10 on the basis of the cycle error determination is calibrated in the laboratory of the Institute of Earth measurement of the Technical University of Vilnius Gedi Minas (Jokelaet al. 2002; Buga et al. 2008, 2011).
The cyclic error determines that the baseline consists of 16 points, and the distance between them is about. 1metre.
Ground laser scanning force during calibration-
Centered on the first installation and distance measurement of force
Focus on goals (
Diameter 6 inch
On another mountain (Fig. 1).
The point cloud of each scan target is about. 39000 points.
From these point clouds, Leica Ltd. uses cyclone software to determine the coordinates of the Target Center
As usual, calculate the distance between the scanner and the target using the formula: S = [Square root ()[([X. sub. t]-[X. sub. s]). sup. 2]+ [([Y. sub. t]-[Y. sub. s]). sup. 2])], (1)where [X. sub. t]and [Y. sub. t]--
Center coordinates of the target ,【X. sub. s]and [Y. sub. s]--
Coordinates of the scanner.
By comparing the calculated distance with the known standard distance, the calibration parameters of the thelaser scanner distance measuring device were evaluated.
Further data processing and calculation are carried out using the standard method of numerical data processing of calibration results (Putrimas 2010).
Table 1 gives the final result.
Table 1 shows that the system error is relatively small (lessthan 1. 3 mm)
Measured at short distances.
These errors are slightly larger for short distances (up to 3 metres)measurements.
The system distance measurement error is shown in figure 2.
Calculate the constant R of the ground laser scanner using all system errors of the measured distance, equal-0. 4 mm.
Figure 2 shows the system error from-1. 3 mm to+0. 4 mm. 2.
The distance measuring device for calibrating the terrestriallaser scanner Leica Scanstation C10 under the kyviskesc calibration baseline is also carried out under the kyviskesc calibration baseline.
The base consists of six pillars, erected in a straight line, with a distance of 1320 between the first and last pillars.
The distance between the inner columns is as follows: 1-2 -100 m, 2-3 -260 m, 3-4 -760 m, 4-5 -180 m, 5-6 -20 m (Joke laet al. 2002; Buga et al. 2008, 2011).
During the calibration process, five different departments of the calibration base were measured.
The longest selection distance is 260. e.
Not exceeding the maximum possible range of ground laser scanners.
Measurement between Pillar 1-2; 2-3; 4-5; 4-6 and5-6.
Laser scanners and targets are forced
With pillars as the center (Fig. 3).
The calibration results are shown in Table 2.
As shown in Table 2, system error from-16. 9 mm to 3.
The constant R of the ground laser scanner is equal to-7mm8. 5mm.
The standard deviation of the system error changes from 0. 00 mm to0.
5mm, the standard uncertainty range of the average system error value is 0. 0 mm to 0. 1 mm.
A significant increase in the system error value can be observed at a distance of more than 100 m.
The system error value is shown in figure 4.
The analysis of the calculation distance measurement accuracy shows that the system error increases linearly with the increase of distance.
This error does not exceed 3 for distances up to 100 m.
7mm, therefore, in line with the technical specifications of the laser scanner studied, I . E. e. 4 mm/50 m. 3.
The calibration of the ground laser scanner horizontal angle measuring device the calibration of the horizontal angle measuring device of the ground laser scanner Leica scanning station C10 is also carried out under the kyviskes calibration baseline.
The experiment was carried out by placing the target on column 5 and column 6.
The accuracy of the horizontal angle measurement is estimated from three different scanner locations, with different angles relative to the above targets.
As described in the previous chapter, the distance measured is measured due to system errors.
Based on the triangular formula, the measured and known (reference)
Horizontal angle.
By applying the coordinates of the target and the scanner, the angle of measurement between TLS and the target can be estimated :[
Mathematical expressions that cannot be reproduced in ASCII](2)here [
Mathematical expressions that cannot be reproduced in ASCII]-
Scanner location coordinates ,[
Non-reproducible mathematical expression in ASCII]-
Coordinates of the target.
Elements of the formula (2)
As shown in figure 5. The well-
Calculate the value of the [angle] with the known Yu cosine formulabeta]: [S. sub. 3. sup. 2]= [S. sub. 1. sup. 2]+ [S. sub. 2. sup. 2]-2[S. sub. 1][S. sub. 2]cos([beta])(3)and [[beta]. sub. t]arccos [S. sub. 1. sup. 2]+ [S. sub. 2. sup. 2]-[S. sub. 3. sup. 2]/ 2[S. sub. 1][S. sub. 2]. (4)
The above formula (4)
Should be used twice during calibration.
When measuring angles [they should be used for the first time][beta]. sub. i]
Calculation from laser scanner data (coordinates).
The next Formula (4)
Determination of reference or true Angle applied to known reference distance [S. sub. 3]
And the corrected distance of the measurement [S. sub. 1]and [S. sub. 2].
The calibration results of the horizontal angle measuring device are shown in Table 3.
As shown in Table 3, the system error varies depending on the following factors3. 5\" to0.
6 \"depends on the clarity of the angle.
The angular constant of the ground laser scanner is equal to A =-1. 3\".
The standard deviation of the system error is from 2. 1\" to 5.
1 \"the standard uncertainty range of the average system error value is 0. 9\" to 2. 1\".
Conclusion The calibration method of horizontal angle measuring device is proposed.
It is based on placing the scanner in front of the calibration reference line and measuring the angle in front of that reference line.
The reference value of this angle is obtained from the lines of the triangle.
It is estimated that the accuracy of the scanning distance measurement device studied is significant (
From ~ 4mm ~ 14mm)
The distance is reduced by more than 100.
In order to determine whether it is a structural defect or a random scanner defect, it is necessary to do more testing on several scanners.
The precision parameters of the laser scanner LeicaScanstation C10 studied comply with the accuracy standards specified in the Egra technical specifications. Caption: Fig. 1.
Cycle error with target title determine baseline loading: Figure2.
The graphical representation of the system error of the ground laser scanner distance measuring device based on the cycle error determination baseline calibration.
= Title: figure3.
Target scanned at Kyviskes calibration baseline header: Figure4.
Graphical representation of system error of ground laser scanner distance measuring device based on Kyviskes calibration baseline description: Fig. 5.
Scheme for measuring the horizontal angle by TLS doi: 10. 3846/20296991. 2013.
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