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7.1.5 Leica RCD105
The Leica RCD105 now offers a new medium format digital
aerial camera system designed specifically for use with its
ALS-series airborne LIDAR systems of Leica Geosystems. The
RCD 105 is designed from the ground up as an airborne digital
metric camera solution in compliance with all applicable
airborne environmental specifications, including temperature,
shock and vibrations. The CC105 Camera Controller is
responsible for the operation and data storage. The image data
is stored on two removable hard discs. Camera control is done
via the operator terminal of the ALS 50. Radiometric
calibration provided which balances the output of all pixels
when uniformly illuminated. The lenses of 35, 60 or 100 mm
focal length are optimised for both RGB and CIR. The CIR use
requires filter/compensating optic to avoid chromatic
aberrations, software and calibration. A single camera controller
is capable of recording data from two camera heads, allowing
simultaneous acquisition of RGB and CIR images. The RCD
105 is available the fastest frame interval of 1/4,000s, Dold &
Flint, 2007.
8. CURRENT TRENDS AND OUTLOOK
The current trends in medium format digital cameras include:
1. A movement towards rapid processing with the aim of (near)
online orthophoto generation, e.g. for disaster management,
security applications etc. This is only possible with direct
georeferencing and several prerequisites, such as precise
online GPS/INS data, a constant interior orientation and a
rigorous bore site alignment, and a high speed and high
quality data management. Compared to digital large format
cameras, single-head medium format cameras have two
important advantages for rapid processing: Due to the single
head, fewer time-consuming preprocessing steps are
necessary before orthorectification. The smaller images also
allow for faster processing of single orthophotos.
2. Multi camera head developments, which will provide a
similar coverage of a standard digital large format camera,
but for a much lower price. By their nature, multi-head
cameras do not acquire vertical images but slightly oblique
images. This may result in geometric and radiometric
problems for example every camera of a multi-head has its
own interior orientation and the relative orientation of the
different cameras may change slightly. In digital large
format cameras, a laborious process is necessary to generate
a single merged image from the different single heads. With
multi-head medium format cameras a less complex strategy
is necessary, e.g. maintaining single image treatment.
3. Forward-motion compensation (FMC) will come, not by
time delayed integration (TDI) but mechanically. Clients ask
for larger and larger ground resolution. In order to get
perfect images with a GSD of 3 - 5 cm, FMC has to be
applied.
4. A trend towards a combination of oblique and vertical
imagery acquisition, e.g. for texturing of 3D-city models. To
fully exploit the information from the oblique perspective, a
minimum of four images from all sides have to be acquired
and managed. Oblique images are difficult to obtain with
standard mapping cameras. Only single- or multihead
middle-format camera(s) systems provide the necessary
flexibility.
5. Compared to large format cameras the digital sensors of
medium format cameras have undergone a strong and steady
increase in resolution, from 6 Megapixels a few years ago to
currently 39 Megapixel. New technologies will increase the
number of pixels even further. Kodak, the supplier for the 39
Megapixel KAF-39000-CA Chip, which is currently in many
medium format cameras introduced a new Colour Filter
Array layout. This technology increases the overall
sensitivity of the sensor, as more of the photons striking the
sensor are collected and used to generate the final image.
This provides an increase in the photographic speed of the
sensor, which can be used to improve performance when
imaging under low light, enable faster shutter speeds (to
reduce motion blur when imaging moving subjects), or the
design of smaller pixels (leading to higher resolutions in a
given optical format) while retaining performance.
Nowadays digital medium format camera systems are mature
airborne systems with high reliability. With the increasing
demand of “near-online” digital aerial data these systems will
become even more popular in the future.
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