Page 139 - Digital Analysis of Remotely Sensed Imagery

Image Pr ocessing Systems 109

in the raster or vector format may be added. Annotative information,
such as legend, scale bar, north arrow, and text, can all be easily inserted.
Data may be classified before they are displayed using enhanced carto-
graphic symbols. It is possible to query a map composition extensively
to determine the identities or attributes of features in a layer that can be
toggled on or off at will. The created composition can be saved, printed,
or transferred to other packages.
4.1.3 File Format
All files in IDRISI consist of two parts, an image file and a document
or metadata file that are stored separately, distinguishable by their
extension. Raster data files are usually stored in the binary format.
However, a wide range of other data types are also supported, such
as unsigned 8-bit integer, integer, real, RGB8, and RGB24 (24-bit band-
interleaved-by-pixel format in the order of blue, green, and red). The
document file contains descriptions of the image file, such as its
dimension, cell size, and ground coordinate system, and so on.
IDRISI has an excellent range of capabilities of importing, pro-
cessing, and exporting raster imagery in many formats. In addition to
common imagery formats like SPOT (Le Systeme Pour l’Observation
de la Terre), Landsat, and Radarsat data, other data formats such as
the hierarchical data format (HDF) from the Terra satellite are also
supported. Data in all major formats can be imported from other
image processing systems, including ESRI (Environmental Systems
Research Institute) ArcRaster, ERDAS (Earth Resources Data Analy-
sis System) Imagine, MapInfo vector, ENVI (Environment for Visual-
izing Images), and ER (Earth Resources) Mapper files, using a consor-
tium of tools. Imported images can be rubber-sheet resampled to a
user-specified coordinate system, or projected to the desired geodetic
datum. IDRISI 15 supplies more than 400 reference system parameter
files and instructions on how to create a desired projection. Data can
be converted from raster to vector or vice versa.
4.1.4 User Interface
In this system's graphical user interface (GUI), all modules are acces-
sible via a main toolbar under seven categories: file, display, GIS anal-
ysis, modeling, image processing, reformat, and data entry. All image
processing functions are further organized into more categories in the
second tier of program menu, such as restoration, enhancement,
transformation, hard classifier, soft classifier, hyperspectral image
analysis, accuracy assessment, and restoration. Common modules
and functions are directly available through icons immediately below
the toolbars. Once activated, a new window is opened for further
interaction with the system. In the new release an Explorer bar has
been added to provide a heads-up reference that enhances file orga-
nization on the fly and that are most likely to affect the workflow of
regular users.