Mohammed al-Idrisi was a geographer and cartographer to the King ofSicily in the s. He headed a collaborative effort to survey theworld which produced a kg silver ball representation of the worldin some detail. This ball served as a primary geographic reference forabout the next years. Where does it come from? It is, however, a fully functional GIS package and iswidely used in educational, government and resource managementinstitutions around the world. What is it?
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Open Source. Professional Development. Remote Sensing. Synopsis and Recommendations The Idrisi software provides a wealth of analytical capabilities at an exceptional price. It also contains extensive import and export procedures and a simple way to interface with other GIS software.
These two things make it a direct competitor of raster and statistical analysis functions offered as add-on modules in many other GIS products. Idrisi is a strong candidate to supplement your main GIS with image and raster analysis functions.
Before you buy a limited or expensive solution, take a good look at this one. This software is also attractive for use in a teaching setting because of its breadth of "Idrisi should be high on your list of possible solutions. It is most appropriate for teaching techniques of raster analysis, environmental modeling, and image processing.
Beginning students will not suffer as much from the inefficiencies and lack of cartographic polish as more experienced people would. Teachers with leanings toward cartography, database management, or computational geometry will not find the support they need from this software.
Potentially you could do almost anything you want with Idrisi. However, trying to use it as your main GIS software could be frustrating. It has an inefficient interface, limited support for vector analysis, and insufficient cartographic capabilities for most GIS needs, although they are rapidly improving. Ratings Capabilities 5 Wide range of grid and image analysis and processing functions. Integration 5 Simple to use API. COM-compliant; ability to import, process, and export many raster and image formats.
Documentation 4 The manuals are pithy and instructive, the help system consistent, compact, and helpful. Authoritative and complete references are lacking, though, so the user is left guessing at some undocumented syntax and error messages. Cool features 4 Good integration and use of metadata.
Fast and versatile projection computations. Ability to create symbol sets to standardize the appearances of maps. Good management of files and folders. Robustness 4 A bit flaky, but little tendency to crash or lose data on Windows NT 4. Accuracy 4 Documentation is unclear about speed-accuracy tradeoffs; alternative algorithms are available to produce faster results, which is good; but the user will need to test any algorithm carefully before relying on it, because different choices may produce different results.
Speed Algorithm speeds are adequate, but not the fastest possible. Display speed is poor in some circumstances: for example, linked zooms of large images can take minutes. Automation Antiquated and severely limited "macro" capability; requires many sequences of operations to get simple things done.
But: decent log file and ability to access macros through VBA. Mapping 2 On-screen images have high spatial and color resolution, but tools for cartographic control are limited or non-existent.
Ease of use 2 Many operations require excessive repetition to complete; heavy demands are placed on the user to perform basic operations correctly; inconsistent support is provided for error diagnosis and correction. Basic interface support, such as window management, is missing. Introduction "GIS" covers a lot of ground these days, so let's get it straight: you can ignore Idrisi if you are a Microsoft MapPoint user or if your only interest is in serving up vector images such as route maps on the Web.
For the rest of us, some part of Idrisi will be uniquely valuable, even if we already have access to high-end GIS software. This review discusses what Idrisi does well, how it might work with other GIS software, and how it might be improved. Its outward appearance belies its capabilities and it would be wrong to compare it either to a compact car or a racing vehicle.
To use it and appreciate it, you have to strip it down to its parts. The parts are Idrisi "modules. Each typically processes one or more input feature sets raster or vector format and outputs one or more data sets almost always in raster format.
Idrisi's "metadata" window. Idrisi does a nice job of maintaining and actually using metadata. Some modules can even recognize and propagate accuracy measurements. Click to enlarge For example, the "toposhape" module classifies each cell of an input digital elevation grid according to its topographic appearance: ridge, valley, convex slope, and eight other categories. The output is another grid of cells, each of which contains a numerical code for the topographic category.
You can execute these modules from the Idrisi Windows interface, from an Idrisi "macro" file, from a separate application written in a language like Visual Basic, Delphi, or C for example , or from other Windows software like Excel or Word.
Later below I will make the case "Sooner or later, even the mapmakers-or their clients-will want the computer to help answer the questions that well-made maps provoke. In short, when you invest in Idrisi you're really getting the parts to the car and you can use them to soup up your own vehicle.
For testing or for simple operations, you can use the parts as assembled by Clark Labs. How it works Further below we discuss the rich set of capabilities included with Idrisi. Before proceeding, though, I want to describe what it's like to live within Idrisi. Clark Labs has written a Windows interface to provide a common, easy to use mode of access to the Idrisi modules.
This interface also performs basic functions such as map display, file selection, text file editing, serving up help screens, and importing or exporting files. The interface is simple and fairly elegant. The main window offers a hierarchical menu system and two dozen buttons as shortcuts to frequently used dialogs. Its status line displays world and image coordinates simultaneously , shows the time, and provides detailed progress monitoring for longer operations. Individual dialogs encapsulate the Idrisi modules, so most of the interface work consists of launching the module dialogs via the menus or buttons.
You can even create menu-level access to non-Idrisi programs. Although this is appealing to the programmer, it can be dismaying to the experienced user. The reason is that hiding beneath this environment is an antiquated command-line system.
Filling out the dialogs requires about as much effort as typing in commands, but you get little in return: like command lines, these dialogs do not identify errors until everything has been filled out; like command lines, these dialogs do not interact with each other by remembering previous file names, for example ; like command lines, these dialogs have to be executed in long sequences to perform some of the simplest analyses.
So, despite appearances, Idrisi's interface exploits few of the advantages offered by the Windows environment, such as the ability to directly manipulate objects visible within a window. Until recently this would have been acceptable, but in comparison to up-to-date interfaces this one feels cumbersome. Screen shot of Idrisi during this review. How many windows are open? I have no idea-Idrisi provides no way to manage them. Click to enlarge Nevertheless, you should give this software a look.
The reason is that you can easily use the modules from within your favorite analytical " The secret lies in the "programming API. In this case, though, it is worth a look even if you are a non-programmer. The programming is pretty simple. Well, it's easier and clearer than the macros, anyway. It looks complicated, but Idrisi's truly context-sensitive help provides just the documentation you need and Idrisi's log file helps create a first cut at it. Then you are done: this stuff is re-usable at the push of a button.
At least one reviewer has called this approach "object-oriented programming. As you can see, it's just the macro language in disguise a "wrapper," in pseudo-technical terms. But the disguise gives you full access to key Idrisi "For a quarter of the price Idrisi will match all those capabilities You have to have an Idrisi license, of course, to get them to run. If you read on below, you will see just how capable this software is. To buy similar raster capabilities from a competitor who will go unnamed you would have to buy their grid analysis module, their image analysis module, and their geostatistical analysis module.
For a quarter of the price Idrisi will match all those capabilities and offer some impressive specialized ones on top. I think it's only a matter of time before someone-perhaps Clark Labs itself-sees where this is going and writes the code to integrate the Idrisi modules with your favorite GIS software, so no programming at all will be necessary. It may be you have a specific need right now, or maybe you're thinking of the software as a long-term investment. Software satisfies needs in two similar ways: by doing a particular specialized task the immediate need or by providing a suite of general capabilities that can be deployed to solve a wide array of problems, some of them perhaps not foreseen by the software developers the long-term investment.
Idrisi modules fit into both categories. Many of them exist to perform some general function, such as overlay, filtering, distance calculations, reclassification, map projection, and so on.
Well-chosen sequences of such functions are the backbone of effective GIS maintenance and analysis. Many other Idrisi modules exist only to perform some very specialized function. For example, the "vegindex" module will calculate 19 types of "vegetation index," provided its inputs are the red and near-infrared bands from an earth orbiting satellite image.
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