9. CONFIGURATION
Size:
4 x 11
; Circ
le spa
cing:
2.0 cm
; Circ
le diam
eter:
1.5 cm
;
5 cm
2 in
nerian
.com
Figure 21: Calibration board used by SceneScan.
for synchronization. PTP provides a signicantly higher accuracy when com-
pared to NTP, and should hence be preferred if available. Like for NTP, the
clock will also be set to UTC and synchronization status information will be
displayed.
When activating Pulse Per Second (PPS) synchronization, the internal
clock is set to 0 whenever a synchronization signal is received. Please refer
to Section 7.8 on page 14 for details on the PPS synchronization.
9.9 Camera Calibration
9.9.1 Calibration Board
The `calibrate cameras' page, which is shown in Figure 20, enables the cali-
bration of the stereo camera pair. You require a calibration board, which is a
at panel with a visible calibration pattern on one side. The pattern that is
used by SceneScan consists of an asymmetric grid of black circles on a white
background, as shown in Figure 21.
The pattern can be downloaded directly from the calibration page. Simply
select the desired pattern size in the `calibration board' drop-down list, and
click the download link. Even if you already have a calibration board, make
sure to always select the correct size before starting the calibration process.
Otherwise the calibration results cannot be used for 3D reconstruction with a
correct metric scale (see Section 8.2).
Should you require a calibration board with a custom size, then you can
select custom from the `calibration board' drop-down list. This allows you to
enter the calibration board details manually. The rst dimension of the pattern
size is the number of circles in one grid column. This number must be equal
for all columns of the circles grid.
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