Instruction manual

Page A-2 Z-12 Real-Time Sensor Operation and Reference Manual
Therefore, setting the interval parameter to 1 second ($PASHS,RCI,1) yields the
highest event time record rate.
Because the 1 PPS signal is being used to record the photogrammetry events, the
period of the 1 PPS signal needs to be set to a value equal to or less than the period of
the EVENT pulse.
The trigger pulse may be TTL-compatible or open collector. Minimum pulse
duration is 100 nanoseconds when the signal is not terminated at the sensor input.
The impedance is approximately 2K ohms.
Use a coaxial cable with BNC connectors to connect the camera trigger output to the
photogrammetry input connector of the sensor.
Time Tagging the Shutter Signal
In this technique, the signal generated by the camera shutter is fed to a GPS sensor for
accurate time-tagging which can then be post-processed with the GPS observations.
Since the time of the picture is not synchronized with the time that the GPS
measurement is taken, the two position computations before and after the shutter time
are interpolated to compute the position of the camera at the time the picture was
taken.
If the GPS measurements are recorded at the rate of one per second, the distance that
the aircraft moves in ½ second is about 100 meters. Therefore, the distance between
the position of the camera at the time the picture was taken and the GPS position fixes
can be as much as 50 meters. The motion of the aircraft during this time may be in
the meter range.
To minimize the errors discussed above, the closed loop technique is recommended.