International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B1. Istanbul 2004
kind at once, most currently available airborne sensor systems
are supported by the CCNS.
For the precise determination of position and attitude of the
airborne sensor, the CCNS can be operated with the GPS/IMU
system AEROcontrol.
pe Tr
TESTS
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e integrated BINGO or BINGO30 AT
software package for Integrated Sensor
Orientation (ISO) and boresight calibration
inside AEROoffice
Fig. 2: AEROcontrol-11d
AEROcontrol consists of the following four components:
e The Inertial Measurement Unit /MU-IId:
The IMU includes three accelerometers, three fibre
optic gyroscopes and signal pre-processing
electronics. The six sensors are attached rigidly to an
aluminium frame. Through wholes in the IMU
housing, this sensor block is mounted directly to the
used airborne sensor. The /MU-IId provides a high
accuracy measurement of the angular rate and of the
acceleration with an update rate of up to 256 Hz.
e The airborne computer unit:
The airborne computer unit collects the raw data of
the IMU and of the GPS receiver and stores them on
a PC-Card for post-processing. It also provides the
time synchronization between the GPS, the IMU and
the used sensor. A real-time platform calculation
allows the use of the information as navigational
input for the CCNS.
e The GPS antenna and receiver:
The system can be operated with a number of
different GPS receivers. The default configuration is
an integrated 12-channel LI1/L2 receiver from
NovAtel Inc..
e The postprocessing software AEROoffice:
AER office provides all functions necessary for the
handling and evaluation of the collected GPS and
IMU data, like:
e tools for handling the PC-Cards
e differential GPS post-processing software
e inertial navigation software
e transformation to the local mapping system
e lever-arm corrections for static and variable
lever-arms
174
Fig.3: Sensor block of the /MU-IId
4. CCNS - ULTARCAMy INTERFACE
4.1.1 Communication in the airborne system
The communication between the CCNS is realized via a RS232
interface and a separate cable for the trigger pulse and the
feedback signal.
Besides the trigger pulse, the CCNS provides the
ULTRACAMp with the necessary information for the forward
motion compensation (height and velocity), with the photo
specific metadata (exposure number, date/time, position, track
over ground) and with the photo specific data from mission
planning (project, area, flightline, segment, waypoint number).
At the instant of exposure, the camera sends a feedback signal
to the CCNS. The approximate position of the camera at the
instant of exposure is calculated in near real time and is sent
back to the camera. The exact time of this signal is recorded
together with the GPS and IMU raw data in the AFROcontrol
computer for calculation of the exact exterior orientation of the
camera in post processing. In addition to the feedback signal,
the camera sends status information to the CCNS. The display
of this information on the CDU enables the pilot or the
operator to oversee the status of the complete sensor system by
looking at the navigation screen.
4.1.2 Mechanical IMU interface
The IMU is fixed mounted inside the ULTRACAMp SU
housing. To install the unit inside the SU, it is screwed on an
aluminium base plate that can easily be fixed to the main
frame of the SU. The mounting provides a stiff and durable
connection to the optical system of the ULTRACAMp,
4.1.3 Mission planning and GPS/IMU post processing
On the software side, the parameters of the ULTRACMp are
available in the mission planning software WinMP, so
automatic flight planning for closed (areas) and open (tracks)
polygons is possible.
For the identification of the camera events in the GPS/IMU
post-processing, the camera events are unambiguously marked
by the exchanged information.
In addition to the on-line event handling all relevant data from
the flight management and navigation system are stored
Ini
