International Archives of Photogrammetry and Remote Sensing. Vol. XXXII, Part 6. Bandung-lndonesia 1999
22
CAT / CAL IN PHOTOGRAMMETRY ON THE INTERNET
Joachim Hôhle
Laboratory for Geoinformatics
Aalborg University
Fibigerstræde 11, DK 9220 Aalborg 0st, Denmark
E-mail: jh@i4.auc.dk
URL: http://www.i4.auc.dk/jh
Commission VI, Working Group 2
KEY WORDS: Computer-assisted learning, computer-assisted teaching, digital photogrammetry, automatic measurement,
correlation, Internet, browser, Java
ABSTRACT
CAT/CAL programs which run on any computer and operating system is the dream of many educators. The Java Virtual Machine
seems to support this ambiteous goal. The reality is something else and many difficulties have to be overcome. The development of
interactive CAT/CAL programs have to take care of the differences in the platforms and tools. On the other hand the Internet gives
access to many other ressources and possibilities which will benefit the CAT/CAL programs. This paper discusses the problems in
development and use of the interactive and Internet-based learning program “LDIPInter”. The topic of “LDIPInter" is automatic
measurement of images which is a central topic in digital photogrammetry. By means of rolling texts, animations and several tasks
with changing data sets the learner becomes interested and active and will understand the process of automatic measurements better
than with text books. Articles, manuals and dictionaries, which are accessable by the Internet, can be used in addition. The
realisation of good CAT/CAL programs requires many resources, and suggestions are made how an international cooperation could
improve the situation.
1. INTRODUCTION
The Internet can be used as a learning tool in combination
with other aids. Especially in distance education, the Internet
will play an important role. By means of the Internet many
new opportunities will be created which can support the
learning. For example:
- search for literature and access to
complete texts of articles
- use of encyclopaedia, manuals and
dictionaries, etc.
- communication between students and
teacher as well as between students
The distribution and use of learning software packages is also
possible. The learning by means of these software packages
is often called “Computer-assisted learning" (“CAL”) or
“Computer assisted teaching” (“CAT”). If the Internet is used
as the platform for a CAT/CAL program various advantages
can be found (compare figure 1). Thanks to the Java Virtual
Maschine (JVM) such CAT/CAL programs are automatically
installed on many different platforms consisting of computer,
operating system and browser. This platform independence
is especially necessary for CAT/CAL programs because
many different systems exist in educational environments
around the world. Furthermore, the latest version of such a
CAT/CAL program can be downloaded from the Internet at
any time. There exists a wealth of share- and freeware which
could be integrated into new CAT/CAL programs. The
development tools (Java compiler, editor, debugger and
applet viewer) are also freely available which may start a
common development at different locations. The use of a
learning program could be monitored (counted) and even
charged.
With all these advantages in mind, an existing and
established CAT/CAL program, “Learning about digital
photogrammetry” (“LDIP”), was transferred into an Internet
version, called “LDIPInter”. First experiences from the
development of this Internet-based CAT/CAL program was
presented in (Hohle 1997). In the meantime, new themes
were added and experiences gained from its use at different
platforms. It is the purpose of this paper to inform about the
new achievements and about the user experiences with this
type of CAT/CAL programs. In the following chapter the
latest version of “LDIPInter” ( 1.14) will briefly be
explained.
2. THE CAT/CAL PROGRAM “LDIPInter”
The Internet-based CAT/CAL program “LDIPInter” explains
the theory behind automatic measurements in images step by
step and provides exercises for each step. Currently, it
contains two themes: “Automatic measurement” and
