Calibration of a Terrestrial Laser Scanner - Institute of Geodesy and ...

3.3 Angle Measurement System 45and —2 mm, only in the scanning mode 'middle' do the residuals increase from ranges of more than 12 m.Considering the residuals in terms of degrees, it can be seen that the values do not exceed 0.01 ° withthe exception of the first three meters, which istranslation from metric values to angular values in short distances.due to the unfavourable geometrical conditions for the10-•—superhigh-•-highhorizontal encoder (15cm)0 100 08^0.060.040.02110 12range [m]horizontal encoder (15cm)—•—sup ärhigh-•-high,\% /\/die0 00""""ï^"""*_£»-»,"^-•^5^«^10 12range [m],s14 16 20Figure 3.22: Residuals of the horizontal encoder based on the coordinate transformationfrom the local scanner systemto the calibration track line system. Top: Residuals expressed in millimeters. Bottom: Absolute values of the residualsexpressed in degrees.Generally, it can be summarized that the accuracy for the horizontal encoder of the angle measurementsystem lies within ±0.01 °. The results obtained by the two different experimental setups fit each other andconfirm the achieved accuracy independently. Considering the residuals expressed in millimeters, it canbe stated that the accuracy of the horizontal angle measurement system isnot as crucial as the distancemeasurement system. Furthermore, the specifications of the manufacturer are in agreement. The precisionfor the horizontal encoder is of a factor of ten better than the accuracy.3.3.2 Vertical EncoderThe precision of the vertical encoder for the angle measurement system is shown in Table 3.5. The precisionof a single measurement (ss) and the precision of the mean value (sm) are also given.The precision of asingle measurement has acceptable values for all scanning modes and are sufficiently high.These valueswere derived from ten repeated measurements within the same experimental setup. The range to the spherewas approximately 3 m. The results are similar to the results derived for the precisionfor the horizontalencoder for the angle measurement system.