Page 147 - Digital Analysis of Remotely Sensed Imagery

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add-on modules expand the functionalities of ERDAS to meet special
image processing needs, such as radiometric correction, use of vector
data, 3D analysis, and visualization. The Vector toolbox is designed
to process chiefly vector data that have found increasing use in digital
image analysis. Vector data may be subset, mosaicked, copied, and
transformed just as with raster data. They can also be cleaned after
their topology has been built within an ESRI Arc structured format. Tools
are available for creating, editing, and viewing vector data, and repro-
jecting them. With the Enterprise Editor, users can manipulate vec-
tors and topology in Oracle 10g. Vector layers may be imported to
ERDAS Imagine and exported to ArcGIS. It is also possible to convert
raster data to the vector format or vice versa in this module. Thanks
to this module, image analysis and vector GIS are more closely inte-
grated than ever before.
Stereo Analyst is a toolbox designed specifically to manipulate
3D models, and to collect 3D features and attributes easily and accu-
rately. Two-dimensional vector layers may be superimposed onto a
digital stereo model so that they can be edited and reshaped to their
genuine positions in reality. The 3D Measure Tool aids airphoto inter-
pretation and quantitative analysis of geographic information. It
enables direct delineation and measurement of the area boundary of
a parcel of land. The 3D Position Tool facilitates determination of the
accuracy associated with existing GIS vector datasets and digital ste-
reo models.
VirtualGIS is a powerful 3D analysis environment in which topo-
graphic data are dynamically visualized as fly-throughs of user-
defined flight paths in an interactive, real-time fashion. Multiple
types of geographic data can also be assimilated in VirtualGIS, for
instance, blending and fading of two images. It is also possible to
carry out interactive 3D models, intervisibility analysis, and create
triangulated irregular network (TIN) meshes in this module.
AutoSync is an add-on module for locating and measuring con-
trol points for georeferencing multiple images and for image triangu-
lation. The automated point matching (APM) algorithm in LPS is
used to find a large number of tie points among two or more overlap-
ping images to georeference them quickly and robustly. AutoSync
makes use of a wizard to provide an integrated and intuitive interface
to the APM algorithm. A large number of points that tie a raw image
to a similar, georeferenced image are generated automatically with
one of four models: affine, polynomial, piecewise linear, and nonlin-
ear transformations (Cothren and Barnes, 2006). Other models such
as Rational Polynomial Coefficient and Direct Linear Transform are
provided to Imagine Advantage license holders. They are useful for
orthorectifying satellite imagery and aerial photographs.
DeltaQue is a module designed specifically for identifying
changes between raw, coregistered multitemporal images. A series of
algorithms, procedures, and processing steps essential in change