International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B4. Istanbul 2004
the hand of the data producer and provider. They have to
prepare a user-friendly human interface to their complex data.
Usually a major developing effort becomes necessary for the
individual governmental offices. However making use of Open-
Source software supports participation at developments made
by other software developers or administrative offices. The
solution very often fits better to the needs of the users.
In this contribution such a solution is presented: The concept
and development of an Internet-GIS for the county
administration in Bad Doberan. The solution was realised with
the MapServer of the University of Minnesota (UMN) on top of
the generally wide-spread Internet Client-Server architecture
WAMP (Windows, Apache, MySQL, PHP).
The data from the authority were prepared partially before their
publication in the Internet with respect to data formats and the
kind of data storage. This part of the work, which has to be
done at the authorities themselves, is excluded in this paper,
even if it is likewise very important to set up this type of
geodata infrastructure. Currently we are developing additional
conversion software especially for that purpose.
In the first part of the contribution necessary terms are defined,
a comparison of Internet-GIS versus conventional GIS is made
and general ranges of application are pointed out. Subsequently,
the functionality of Internet-GIS is presented and technology
configurations used in practice are illustrated. In the next
section the concept of the Map Server for the district
administration and its technical realisation is described. Thus
the presented solution can be arranged well in the technology.
At the end a summary follows and an outlook is given in
particular with respect to the advancement of interoperable
solutions with several distributed data providers.
2. TERMS AND RANGE OF APPLICATION
The principal difference between a GIS and an Internet-GIS is
that in the latter case the data are made available over the
Internet. While a GIS can be a stand alone solution, i.e. only
one program on a computer, an Internet-GIS is always a Client-
Server solution. Nevertheless the term Internet-GIS is
understood with different meanings, range of applications and
functionality (Piepel, 2002). Other terms such as Online-GIS,
Web-GIS or MapServer are also often equated with the term
Internet-GIS. There is no consensus on the use of the term
referred to the functions and application possibilities lying
behind. To keep the individual solutions apart and to be able to
classify it, a classification related to functionality and
technology may help for differentiation.
Depending upon the range of applications of the Internet-GIS a
set of functionalities is needed. Simple functionalities like
interactive mapping (zoom and pan) with spatial queries of the
actual data and a visual overlay of the information can be
regarded as the technological standard. The following ranges of
application can roughly be differentiated:
— Simple Information and Query Systems, which present
interactive maps with different themes and thematic
data in a standard internet environment (browser) or
with extensions (Plug-in). These are useful e.g. within
the municipal range for the publication of information
via Internet, especially for the citizen and visitors.
— Specialized Geo-Information Systems, which make
additional services available for the public or only for
a reduced circle of users. Functionalities would be
something like address detection, route finding or
simple analyses of data.
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— WWW-based Gl-Clients with access to a central
resource, which provide a number of extended
functionalities like measuring distances, analysis and
intersection of the data, export, changing attributes,
and diagrams etc. Such types of systems are usually
used in the Intranet and Extranet, because it requires a
support/training of the users and a user administration.
The clients can be used in authorities being a more
economical alternative to proprietary GI-Viewers and
Desktop-GIS and allowing a data exchange over
locations as well as to mobile stations.
— Geodata Pórtals: Internet applications to provide
and/or sell large data sets. The data usually are
coming from different geodata servers. Applications
are within the municipal range e.g. in the trade area
marketing or in the sales of cadastral data.
A crucial criterion for the choice and development of an
Internet-GIS is the available speed and the quantity of the data
which can be transported. The optimum would be a fast
connection line and few data, but in reality the exact opposite is
oflen the case. The setting up of the appropriate parameters
often results in an optimization task. The functionality being
made available depends however only on the requirements with
respect to system and the available resources for financing
and/or development costs. The requirements by the users rise
fast. Problems often result in that certain desires and/or
functions can not be operated within the same exisung
technology, with which the Internet-GIS originally was
introduced.
For the estimation of the effort to supply certain functionality
the following aspects have to be considered:
— What do the users want to do with the Internet-GIS?
— Which groups of users will exist (Intranet/
Internet/Extranet)?
— Which speed is available (net parameters)?
— Which extensions are necessary for clients and servers
(plug in, script support)?
— For client and servers, if necessary, separate license
costs have to be paid (use of Open Source as an
alternative?).
— Which Internet browser and operating systems have to
be used?
— Which data formats are available and/or have to be
used?
— Which personnel expenditure for the development,
service and maintenance of the system can be
expected?
The requirements usually rise by using the system. The
designed system should be flexible enough to fulfil current
demands and to be extended in future.
3. FUNCTIONALITY AND TECHNOLOGY
The client-server technology, by which geo data and functions
are made available in an Internet-GIS, may have the following
characteristics:
— The speed depends on the quantity of the data which
will be transported.
— The quantity depends again on the data type.
— The load of the data processing can be distributed on
client and servers.
— Client-server technology offers multi-user ability for
reading and possibly writing access.
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