International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B1. Istanbul 2004
shifted on the screen. For convenience another monitor may be
connected to the system.
Having in mind that imagery reconnaissance is not only object
detection but precise location as well, the Authors implemented
in the system a module for position tracking on a numerical
map based on the GPS data. Navigational and other
alphanumeric data may by also annotated on the recorded
images.
Camera head
During the system concept development phase it was assumed
that it would be based on the European television standard
(PAL) for color images and CCIR for monochromatic images.
To record images in the specific spectral channels in a wide
band of the EM spectrum, the system is composed of a few
separate video cameras.
Each system channel is related with a different spectrum region.
The spectrum band of a channel is determined by the
transmission bands of the applied optical filters. This solution
enables quick modification of the spectral resolution of the
system by means of replacing the applied optical filters.
Three 1/3" class monochromatic cameras are applied in the
multispectral video set.
They provide imagery information from the same area in UV
and NIR bands. The recording band is limited by the
transmission of the applied filter on one end and by the CCD
matrix sensitivity on the other. SONY DX-950P camera was
used to acquire images in 3 spectral channels (R, G, B) of the
visible spectrum. This camera is equipped with 3 photo-mosaics
providing precise projection of the spectral information.
Fig. 2. 3CCD Sony DX-950P camera.
Recorders
A software & hardware computer system was constructed for
recording the digital data stream that includes the images from
selected spectral channels. It is equipped with a special array of
fast 140 GB hard disks that provides fast recording and
retrieving of data. The HDs array enables continuous recording
of uncompressed images from 6 channels at the same time for
over 40 minutes and for appropriately time longer for fewer
channels.
The recorded sequences of images may be displayed on the
monitor screen both as images from specific channels and as
images composed of various bands. During displaying a
recorded sequence from any three channels selected from both
bands another “composed” image may be created. This is to
enable fast checking of the ,,common differentiating power" of
the observed objects for the selected configuration of spectral
channels.
The created composed image may be saved in a new video
sequence in ,.avi" format. A single image from the sequence
may also be saved as a disk file in ,..tif" format.
ASSESSMENT OF THE IMAGERY ACQUIRED BY
MEANS OF THE SYSTEM
Resolution is the factor determining the capability of
distinguishing an object in an image. This section includes an
assessment of the quality of the images based on their
resolution.
Determination of the ground resolved distance of the images
Determination of the ground resolved distance (GRD) was
based on a calibration target.
A calibration target shall be understood as a special object
deployed on the ground for the purpose of determination of the
ground resolved distance of the observation devices.
The object is defined by its dimensions as well as frequency and
spatial characteristics of reflectivity. These objects are usually
flat modular constructions composed of elementary planes that
are deployed appropriately on a selected ground.
A stripe pattern of specially defined dimensions and selected
contrast between the dark and light stripes is painted on the
surface of the object.
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Fig. 3. Three-stripe calibration target.
Images of the calibration target were recorded using the system
and the ground resolved distance GRD was determined using
the images.
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Fig. 4. Imagery acquired from the height of 300 m.
GRD {m}
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