ESS N LE
The figure above traces the development of the
current applications to their roots in systems developed for
the government and other customers. The areas labeled
“technology insertion” were developed on SAIC internal
development funding, in support of planned government
efforts and with the intent of generating a commercial
production capability.
SAIC, at the present time, does not sell these
integrated photogrammetric systems, but uses them
internally to generate data for various commercial and
government applications. We are one of the U.S. Geological
Survey's National Digital Orthophoto Program contractors,
and under that program have produced or have in production
over 5000 digital orthophoto quarter quadrangles using the
GIS MAGIC™ system which is described below. That same
system has been used to produce high resolution
orthophotos at a ground resolution of 0.125 meter for
Tauranga, New Zealand.
For various customers, we have developed
processing capabilities which we are adding to our integrated
solutions as the need arises. Of course, applications
developed for a specific customer must be tailored to operate
properly within the environment used by that customer.
Within these limitations imposed by the customers for
compatibility with their systems, we make a concerted effort
to ensure that the technology which we develop for them is
compatible with our internal integrated system, so that we
can incorporate those capabilities into our internal systems
at minimum expense. We benefit internally from this
approach, because our integrated internal systems are
continually growing in capability, but the government
customers who pay for the development also benefit because
of the potential for re-using algorithms developed for other
government customers to minimize new development costs.
2. The GIS MAGIC™ System
The roots of the GIS MAGIC™ system are in a
system which SAIC developed for the U.S. Defense Mapping
Agency, called the Digital SAR Workstation (DSW). DSW
was originally designed for mensuration, triangulation,
orthorectification, and mosaicking of Synthetic Aperture
Radar (SAR) imagery. However, the generality of the
approach used in that project allowed the same
orthorectification software, and the solution framework of
the aerial triangulation software, to be used for optical
imagery as well. The current system will process SAR, aerial
photographs, and SPOT data, with the capability of easily
adding dynamic camera models from various reconnaissance
sensors. The various photographs are essentially objects, in
the object oriented programming sense. Each photograph
comes with a key to an imagery type, which dictates the
software to be used to produce the projective equations and
the partial derivatives. These elements are simply entered
into the appropriate slot in the solution template. This is
the key to an integrated photogrammetric workstation; the
basic software architecture is entirely modular, and new
sensors fit into the existing framework with only new
projective equations and their partial derivatives needing to
be computed.
Gi N Ca i EE A EPOR E E
The key to the generality of the GIS MAGIC™
system is in the fact that rational functions are used to model
the sensors in all operations beyond the aerial triangulation.
The use of rational functions allows a common mathematical
formulation for all imaging sensors, and thus allows the
applications software to operate without regard to the actual
sensor involved. In fact, combinations of sensors may be
readily accommodated. The rational function has the form:
x=R, (X,Y. 2D
y= R, (X, Y,Z)
where:
® x,y are image coordinates (these could just as well be
line and sample pixel coordinate)
e X,Y,Z are ground coordinates of the point in some
desired reference system
e R, and R, are rational functions of the form:
R,= P/Q, R, = S/Q
where P, and S are polynomials of the form:
a+bX 4cY 4dZ «eX? «Y? «gZ^ +hXY HYZ +XZ
+kX° +1Y* +mZ* +nXY? +0X°Y 4pXZ? «qX^'Y +rYZ
-5Y?Z
and Q is of the same form, with “a” set to a constant
1 to preclude an ambiguous scale.
The evolution from a system for processing SAR
data to one which processes standard aerial mapping images
is not a simple transition. It comes from the adherence to
the tenets expressed in the introduction to this paper,
namely modular construction, with an eye to the eventual
goal. Not only does SAIC benefit from this approach; the
government also benefits because of the case of
maintainability and modification of the software.
The system is hosted on a Sun SPARC -S-Bus
workstation conforming to IEEE 802.3. The Sun hardware is
enhanced with a Tech Source Image Display board to permit
high speed display of imagery. The Tektronix 1024x1024
display provides high resolution monochrome viewing.
Stereo viewing is achieved with an active liquid crystal
polarizing screen, which permits the use of passive
polarizing eyewear. These passive glasses are less bulky,
easier to use, do not require batteries, and are much less
expensive than the active eyewear used in some other
displays.
3. USE OF GISMAGIC™
The GIS MAGIC system is designed to derive image
maps which are precisely geocoded to an absolute coordinate
frame. Every pixel in the output image can be related exactly
to a specific location in ground space. In order to
accomplish this geocoding, the photogrammetric imaging
event must be precisely modeled. GIS MAGIC™ contains the
ability to rigorously model the taking geometry of the
photogrammetric camera. Although GIS MAGIC™ has the
capability of performing the aerial triangulation solution, it
will also accept solutions performed by outside service
firms, when it is determined that such an outside service is
cost effective. During the planning process, the hardcopy
photo prints are placed on a digitizing table, and the
position of the chosen control and pass points is recorded
relative to the fiducial coordinate system, so that patches of
124
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B2. Vienna 1996
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