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Title
Special UNISPACE III volume
Author
Marsteller, Deborah

UNISPACE III - ISPRS Workshop on
“Resource Mapping from Space”
9:00 am-12:00 pm, 22 July 1999, VIC RoomB
Vienna, Austria
ISPRS
support of a data base of images (ScanEx Catalogue
Manager),
transfonnation of the images into geographic
projections (Image Transformer),
thematic image processing (ScanEx NeRIS).
'Resurs Receiver’ application (Windows 95/NT). The
application performs the following functions:
tests the station,
calculates a schedule of the satellite passages through
the station visibility zone,
controls the entire system and data stream during a
reception sessioa and in particular:
controls the antenna in accordance with a pre
calculated track and measured input signal levels,
locates bit sequences identifying raster image scan
lines in the input stream,
records properly aligned data to a hard disk,
partly displays the data as an image in the application
window,
indicates the input signal level,
indicates the station current status (time, an amount of
recorded data, free disk space, status of a bit and frame
synchronization, current antenna position, tracking
errors, etc.),
corrects the pre-calculated track in auto-track mode.
All ballistic calculations (scheduling, antenna tracking) are
carried out from standard NORAD-TLE orbital elements
available in the Internet. Acceptable are elements of up to 10
days age.
To calculate a schedule, a user must point out a TLE file name
and time brackets for the schedule (up to 10 days) in the
application options. The schedule is displayed in the application
window. The user can edit it - select passages to receive, specify
a transmission mode for every passage. The schedule can be
saved as a text file and afterwards - until it is expired - can be
loaded into the application from this file.
After the application is loaded and the schedule is loaded into the
application, the program permanently compares the current time
with the start time of the closest passage. In the proper time, the
application activates itself (if it is in a background by the
moment) and starts the reception procedures: controls the
antenna, reads data from the interface, checks the data for the
image identifiers and - after the identifiers are found - records
and displays the data.
Taking into account an age and quality of practically available
ephemeredes, the track calculation accuracy is usually not
sufficient to keep a satellite witliin the antenna beam during the
whole passage. Therefore the application has so-called "auto
tracking" mode. In this mode, the application periodically shifts
the antenna position from a calculated one in different directions
by a small angle. Statistically analyzing a dependence of the
input signal level on the shift direction, the application corrects
the pre-calculated track.
The reception can be stopped by the user's command or
automatically - if no image identifiers are found in the input data
during a certain time. If the signal is accidentally lost and a
passage is not over, the reception can be immediately restarted.
In this case the application sets the antenna to a position
corresponding to the current time, opens a new file to record
data, searches again for the image identifiers and so on.
Actually, the only user's duty after the schedule is calculated is to
observe the image quality at the PC display and stop the
reception when the quality falls down at the end of a track (or
restart the reception in case of an accidental loss of signal). Of
course, the application can do it itself but it needs perceptibly
more time (and therefore - the disk space) to make a decision.
Received data are written into a file as a raster type image with
an extendable header. The header contains a usual list of the
image characteristics (a number of lines, number of pixels in a
line, number of spectral cliannels, start time, satellite name,
imaging mode, etc.). Besides, the satellite orbital elements are
written in the header in a binary representation for georeference
purposes (see also descriptions of ScanViewer and Catalogue
Manager).
Also we would like to send you more detail information about
ScanViewer, Catalogue Manager applications and the
information concerning the operational work with ScanER
receiving station.
'ScanViewer' application (Windows 95/NT). The application
is intended in the first place to look through an image, assess its
quality and contents, select and save fragments for the following
storage and thematically processing.
The application enables to:
get a detailed annotation of an image file,
view any rectangular fragment of an image with an
arbitrary' sample step in a gray-scale, pseudo-color or
"true color" (three-channel) representation,
locate an image geographically and overlay a map onto
the image,
correct the geographical location using unambiguously
distinguishable objects in the image,
save any rectangular fragment of an image to a new file
of the same format (thus making all of the ScanViewer
functions applicable to this file),
print any image window and export it to a Windows
bitmap format file,
export image into Image Transformer application.
A size of a loaded image fragment and number of simultaneously
loaded fragments (i.e. image windows) are restricted only with
the available memoiy.
A geographical reference as calculated from the satellite orbital
International Archives of Photogrammetry and Remote Sensing. Vol. XXXII Part 7C2, UNISPACE III, Vienna, 1999
73