International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part Bl. Istanbul 2004
Because of it's multi sensor multi spectral design the camera
also fits perfectly for remote sensing application, like forestry
analysis or agriculture monitoring.
The DMC is a wide angle camera with a focal length and a
field of view similar to a RMK TOP 15 film camera.
The highest benefit of the new digital camera technology will
be an increase of the flying hours per day and the flying days
per year because of it's higher radiometric quality comparing
to film. It will be possible to fly under worse light conditions
or with lower sun angles and still fulfill the quality
requirements of the mapping standards.
Since the mid 80's a forward motion compensation FMC is
used for aerial film cameras to improve the image quality and
to avoid image blurring. Nowadays all aerial survey flight
projects required a camera system with FMC. Because of the
frame sensor technology the DMC has an implemented
electronic FMC, which is a huge advantage and not possible
with CCD line sensors. A time delayed integration TDI is
used to generate the FMC. For large scale mapping project or
for photo flights with long exposure time ( weak light
conditions ) a FMC is a perquisite.
For high resolution four 4k x 7k CCD frame sensors are
mosaicked to a large format image frame with central
perspective and very stable interior geometry. The final
image size is 13824 x 7680 pixel. The footprint of this image
has the same width of a film based aerial image ( across track
) and approx 60% of the length ( along track, in flight
direction ). This is a very important information, because the
number of flight lines will remain the same comparing to a
film camera and so the flying costs.
The DMC is a “Cessna 206 class” camera, which means the
system will fit into the majority of all survey aircraft in use
with respect to it's power consumption and it's size and
weight. A user can fly the camera in a single engine aircraft.
The aircraft installation is pretty much the same as for a film
based camera like the RMK TOP. A DMC will fit into all
aircrafts modified for 9.5" film cameras.
5. FDS FLIGHT DATA STORAGE
To store the raw image data during the photo flight a reliable
powerful mass storage device has to be part of the system.
For further data processing the handling of this device has to
be very user friendly. The DMC camera system is using
flight data storage unit FDS, three units are required for a
system, each FDS can store 250 GB of data, which means in
total 750 GB, equivalent to 2200 aerial images.
The FDS uses standard high speed fiber channel interface
technology, it will be installed in the aircraft with a base
plate, usually mounted to the seat rails of the aircraft.
The size of one FDS is the same as the size of a small tower
PC, the weight is approx 20 kg, the power consumption is 60
W. The FDS can be installed and removed without
disconnecting cables and without using any tools. It will be
automatically powered up and down by the DMC camera
module. If multiple FDS’s are available, an exchange will be
possible in the air during the photo flight to extend the
storage capacity.
Figure 5 flight data storage unit FDS
The FDS has a very reliable and ruggadized design, it
contains two SCSI hard disk in a hardened pressurized
enclosure. It can be operated up to 5000 m or 16000 ft (
8000 m or 26000 ft are optional available) flying altitude in
an non-pressurized aircraft. The FDS is extremely robust and
shock proofed, data safeness is absolutely assured.
For image data post processing the FDS can be
connected directly to a workstation in the office via a
standard fiber channel interface.
The FDS is a flexible and versatile data storage system,
designed for airborne operation.
6. DATA HANDLING IN THE FIELD
After an aerial photo flight mission is completed the crew has
to “develop” the digital film. Very often the airplane is on an
“outbound mission” where the crew does not have access to
the ground based post processing facility or the airplane has
to get ready for the next mission as soon as possible. It will
be required to download to raw image data to a removable
media. To perform this task Z/I Imaging had developed a
mobile field data copy station. This copy station can be taken
on-site by the crew with the aircraft and used in the field for
data copying.
With the copy station the raw DMC image data can be
downloaded from the onboard mass storage device to a
removable media like hard disks, USB disk drives or tape
drives. The user can copy the data either in the aircraft, in an
office or hangar at the airfield or in a hotel room. The
computer is equipped with 3 fiber channel interfaces to
connect the 3 flight data storage units FDS and to ensure a
high data transmission rate. A full set of FDS with approx
2200 DMC images can be copied in less than 4 hours to
removable IDE disk drives. The copy process runs in batch
mode , which reduces the interaction with the operator.
After the copy process is completed, the media e.g.
removable hard disk drives will be shipped to the home
office like an undeveloped film.
The copy station can also be used as a utility for on-site
image quality inspection. Software tools are provided to
perform a quick view of the acquired image, the radiometric
image quality can be evaluated immediately. This is a benefit
against the film based camera, because the user does not have
to wait for the film development and gets an immediate
feedback on the success of the mission.
A block diagram should illustrate the data flow.
Interi
Fig
Ther
post
data
migh
The
of in
and t
Digi
creat
durir
proc
line |
7.1
For «
is to
geon
mov
abou
expo
Unit
