Vendor
Clark Labs
Clark University
Worcester, MA 01610-1477, USA..
508-793-7526,
www.clarklabs.org
idrisi@clarku.edu

Release Date:
May 2001;

latest download patch
May 2002

Hardware
Pentium III+ preferred

64Mb RAM

200Mb disk space

1024x768 graphics resolution and 65,000 colors (will run with 800x600 and 256 colours and 16mb RAM)

Software
Windows 95/98/ME
/XP/NT(3.5)/2000

Cost
$1500 (commercial),
$600 (academic),
$250 (student)
(for full price list, see: www.clarklabs.org/  
 
Distribution Medium 
  CD-ROM

Executive summary

This is the 10th major version of the popular raster GIS and image processing system since its initial release 15 years ago, and the second 32-bit version designed for Windows NT (and equivalent). This version builds on the interface from the first release and adds several new features within over 200 modules, related to GIS modeling, processing of satellite image data and import of both raster and vector data.

The new Macro Modeler provides a graphical modeling environment to simulate multi-process functions, and there is added functionality to several areas of pre-existing strength, such as decision support tools, change and time series analysis, hyperspectral analysis, image classification and surface modeling. Idrisi continues to be a leading package in popularising GIS and image processing.

Features
The Idrisi system contains over 200 independent modules subdivided into menus for file import/export, display, analysis, modeling, image processing, reformatting and data entry. It is impractical to list all modules here, but rather to highlight major features and changes in this release.

Import/export enables file conversion with products such as MapInfo, ERDAS, GRASS, Surfer and ESRI. The routines to exchange between shapefiles, generate files and raster GRID formats have been improved and there is a helpful starter comparison betwen Idrisi and Arcview terms and formats. Importing and display are simultaneous and instant with most files used. (Figure 1.)

The central GIS analysis menu contains submenus on database query, mathematical, distance and context operators, statistics, decision support, change and time series and surface analysis, which together comprise almost half the total software modules (91) and characterize Idrisi as a product that best embodies the distinguishing difference between a GIS and a mapping system. The Decision Wizard adds to the substantial section of decision support tools, assisting in weighting criteria in decision-making to create a single output layer, perhaps the guiding process in developing GIS philosophy. Change and Time series analysis is one of the largest sections in the Idrisi menu, to service increasing demand for environmental monitoring. New modules include change vector analysis and Markov chain analysis, used to predict changes between categories in land cover. (Figure 2.)

Figure 1. Import Menu.

Figure 2. Change Vector Analysis - CVA.

Only the surface analysis section has an additional submenu for interpolation, geostatistics, topographic variables and feature extraction, including an option (toposhape) that extract 11 types of features, such as peaks, ridges, saddles, concave and convex slopes, and incorporating both grid and TIN models. New developments include FLOW and WATERSHED modules. (Figure 3.)

The modeling menu presents four options. The first is the slick new Macro Modeler, which develops graphical flow models that incorporate analysis functions simply added and moved by a drag and drop interface in order to answer a “what if” scenario. Like all Idrisi modules, it is well documented and a sample online tutorial provided, which examines the potential patterns of residential growth, based on factors such as slope, proxmity, and existing concentrations of land use. (Figure 4.)

Figure 3. Flow.

Figure 4. Macro Modeler.

The Macro Modeler goes a long way towards addressing past criticisms that a process might require the tedious generation of multiple intermediate layers although cheap large disk drives have made storage less critical. Other modeling options are the Image Calculator (algebraic overlays), Command Line macros and the Applications Programming Interface (API), which has its own 40-page manual and quick start tutorial for integrating high level languages to control Idrisi modules, such as Delphi, C++ and Visual Basic.

The image analysis section is second only to GIS analysis in size, with 65 modules. In this release, new modules include mosaic, atmospheric correction and several new options for the already strong foci in classification (spectral unmixing and linear discriminant analysis) and hyperspectral data analysis. The addition of a FLOOD module to create training areas by neighbouring threshold values avoids the potential problems associated with user-drawn polygons.

The most recent free download supports the import of HDF (Hierarchical Data Format) files, ASTER and MODIS data and import/export for ERDAS Imagine and ER Mapper. Additions to the Change and Time Series section are also intended primarily for multi-temporal satellite imagery. The Image Analysis modules continue to provide options not always present in industry digital image processing packages, such as standardised principal components analysis, which can be critical in scene comparison as the potential effects of global warming are examined.

Performance
While the given requirements prefer Pentium III or higher, performance was very acceptable on my end-of-millenium Pentium II (400Ghz), including the generation of drape perspectives from imported datasets (2000 x2000), although the user-friendly GUI might be enhanced in speed with a parallel command line option. Having bemoaned the lack of a UNIX version for several years, we can now run Idrisi in our Linux-based lab, using software that loads Windows from Linux (does anyone use Windows by choice?).

Documentation
Documentation has been a strength of the package since its birth; this is the first version that does not provide hardcopy manuals, but instead makes them available online as .pdf documents. There are two user guides: Volume 1 summarizes GIS basics including database development, principles of remote sensing, georeferencing and cartographic display, while Volume 2 deals with more advanced concepts such as uncertainty management, decision strategy analysis, and image processing options. In addition to describing software options, these contain some of the most clearly written descriptions of GIS principles and processes that I have seen and function in part as a general GIS reference resource. A third 238-page tutorial volume contains 36 exercises using sample data with step-by-step instructions and included principles that complement the user guides.

In addition, one can purchase five workbooks in the UNITAR series (United Nations Institute for Training And Research). These cover applications in Change and Time Series Analysis, Forestry, Coastal Zone Research and Management, Mountain Environments and Hazard Assessment and Management. The website also features a substantial image gallery section for an impressive array of project examples using the software, as well as links to application examples by users and a recently added Analytical Notes section.

Technical Support
Technical support is provided free for the first 60 days after purchase and is available for $200 (individual license) or $400 (Lab kit) thereafter. Assistance by email and/or telephone is prompt and able to problem solve. For convenience, online technical support is a direct connect within the software. The wide distribution of Idrisi has also generated a pool of expertise world-wide and several international centers; users may exchange experiences and questions by joining the user forum list.

Ease of installation
Installation was very straightforward (just insert the disk and hit the “next” button as prompted) and proceeded without error, completing within five minutes.

Ease of use
Idrisi was created by educators and it shows. The earlier DOS command line versions were easy to use, and the subsequent Windows versions no less so. Errors resulting from improper input display non-cryptic messages; online help is clearly written and any user should first run through the appropriate training exercises with supplied data.

Pros
There are several reasons why Idrisi has become one of the most widely distributed raster GIS software. The clarity of the training exercises (with provided datasets) and explanation of GIS principles is exceptional. The wide range of analysis and modelling operations provide users with a powerful set of tools that highlight the potentials of the core of GIS while also retaining effective map display creation. The combination of raster GIS and digital image processing modules in an integrated package is likely unsurpassed in the GIS market. Attention to areas of increasing demand, such as Change Analysis reflects a flexible response to users’ needs.

Cons
As a raster GIS, vector operations are predictably more limited although the associated Cartalinx software enables vector input and topology building and can be linked to databases such as Access. In comparison with “industry-standard” image processing systems, I have found two minor inconveniences in displaying satellite imagery: first, the need to generate a composite layer to display a three channel color composite satellite image is an added step versus being able to interactively switch channels (for example, Thematic Mapper 3-4-5 versus 3-4-7); secondly, three-dimensional perspective images draped over a DEM, on steep slopes may include thin slivers without data, although these are only visible with zoom.

Recommendations
The combination of GIS modelling options and image processing functions along with ease of display, affordability and well-documented exercises continue to make Idrisi a leading choice in GIS education and training and for researchers and consultants whose needs are aimed more at modelling applications than the building of attribute databases, and training of GIS technicians.

Unlike most acronymic GIS packages, Idrisi is named after a 12th century cartographer-geographer-botanist. Among other achievements, he created a representation of the known world in his time (used by Columbus three centuries later). The software named in his honour is well-suited to extracting knowledge from the increasing plethora of data collected by a host of satellites and ground investigation.