Page 142 - Digital Analysis of Remotely Sensed Imagery

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Essentials through addition of several more functions, such as
mosaicking, surface interpolation, advanced image interpretation
and orthorectification. Imagine Professional contains more classifi-
cation and spectral analysis, and radar processing utilities than
Imagine Essential. In addition to all those modules included in both
Essentials and Advantage, it also encompasses add-on tools for
complex image analysis and modeling, radar data analysis and
advanced classification. The graphic spatial data modeling module
in Imagine Professional allows the user to create and run models to
analyze images efficiently and flexibly. Core to Imagine are several
important modules for data display (Viewer), exchange (Import),
data preparation, image enhancement (Interpreter), and classifica-
tion. They are elaborated on below.

4.2.1 Image Display and Output
ERDAS Imagine has a versatile and flexible capability in image display
(Fig. 4.2). Single and multiple (at most three) bands are displayed in
grayscale or as a color composite. Multispectral bands can be displayed
simultaneously in multiple viewers. The displayed image may be
panned or zoomed at will through appropriate buttons in the toolbar.
Special facilities are provided for locating a particular point on the dis-
played image via its coordinates, expressed as row/column or east-
ing/northing, depending on the geometric properties of the image. In
addition, multiple images can be displayed on top of each other in the
same viewer. Special tools (e.g., swipe) are available for viewing a por-
tion of the top image and the bottom image simultaneously. Vector lay-
ers may be displayed on top of the displayed raster imagery. The dis-
played image can be queried, as well.
Processed results may be output using the Composer module
that allows an image to be added to an empty map. Other carto-
graphic elements such as legend, scale bar, and north arrow can all be
added to it. The composed map may be saved in a number of formats.
However, it is very difficult to produce a perfect map composition
using ERDAS Composer because of its limited range of fonts.

4.2.2 Data Preparation
More than 130 image formats, even non-remote sensing DEM data,
are recognizable by ERDAS Imagine. Advanced Spaceborne Thermal
Emission and Reflection Radiometer (ASTER), Indian Remote Sens-
ing (IRS), Thematic Mapper (TM), and Advanced Very High Resolu-
tion Radiometer (AVHRR) data can be read directly into the system.
In addition, images saved in all major graphic formats can be imported
from and exported to other systems. Furthermore, ERDAS Imagine
also supports some vector file formats such as ESRI shape files, and
vector coverages.
With ERDAS data preparation functions, it is possible to project
an image to a specified new coordinate system, or geometrically