64 
countries. (More than 9000 students from 145 
countries have attended various remote sen 
sing courses at ITC.) This means that avai 
lable technology is periodically screened for 
its appropriateness and cost effectiveness. 
Where necessary, R&D effort is directed to 
developing prototype systems such as per 
sonal RS and GIS workstations and a RS and 
GIS training package. 
The increasing importance and use of digital 
image processing techniques calls for more 
and better education in using these tools. 
While access to RS and GIS systems, was 
previously limited, because they were imple 
mented on expensive equipment, the recent 
developments in microcomputer technology 
have provided the means to teach larger 
groups of students in using image processing 
tools. 
In response to a number of recognized 
deficiencies, necessities, and opportunities 
regarding the training of students in image 
processing techniques, an educational pac 
kage for teaching RS and GIS has been 
developed. It is named ‘Alexander" in recogni 
tion of Alexander von Humboldt (1769-1859), 
one of the fathers of modem physical geog 
raphy and botany. 
The potential users of the system will be 
students of the earth sciences, with special 
consideration of students from Third World 
countries. They are expected to have a good 
working knowledge in their disciplines and a 
theoretical introduction to image processing. 
2. Hardware configuration 
The Alexander system is written for the 
Archimedes, a low-cost. 32-bit reduced inst 
ruction set computer (RISC) with one Mbyte of 
memory which can be extended to two or four 
Mbytes. The memory can be interactively 
allocated to various slots, e.g. to fonts, RAM 
disks, sprites or relocatable module areas. 
The operating system, called RISC OS, is 
embedded in a WIMP (windows, icons, 
menus, pointer) environment, similar to that of 
the Macintosh. Its features can be addressed 
through computer languages such as C or 
BASIC so that software written for the Archi 
medes can be standardized to give each 
package the same look-and-feel” (figure 1). 
Figure 1: 
The Alexander icon as it 
appears in the directory 
and on the icon bar. 
A window is an area on the screen within 
which the program will operate. It is entirely 
up to the programmer to define the window’s 
properties, e.g. its size, colour, and functions. 
Windows may be much larger than the 
physical screen area, but. using scroll bars, 
any part of the window can be brought into 
view (figure 2). 
The WIMP provides a very intuitive operating 
environment. Saving a program, for instance, 
is done by dragging the file with the mouse to 
the directory viewer. The three-button mouse 
is sufficient for almost all operating system 
commands. The left button is defined as 
SELECT, i.e. to select a menu item, while the 
right button, named ADJUST, usually has the 
same function, but the pop-up menu stays on 
the screen after the selection. The middle 
button, the MENU, is commonly used to bring 
up the pop-up menu (figure 3). 
A pop-up menu is a special window from 
which the user can make selections. Sub 
menus are easily created and indicated by a 
small arrow to the right of the menu item. The 
menu is usually attached to a work window 
and is brought up by a mouse click, hence the 
name pop-up menu. 
A dialogue box is a another special window, 
containing various icons which are used 
mainly for user interactions. Icons can have a 
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