summa lies
J.E. Drummond - A review of the management of error with-
in the GIS environment
This paper gives a review of currently applicable error
management techniques which can be used in a GIS.
The paper begins by stressing the role of maps in GIS - both
as a source of data and a product, indicating that error in
maps either as sources or products will lead to bad decision
making. After a discussion of what a GIS is, it is concluded
that a GIS must be able to handle error both in the data to
be processed and in the models used to perform the Informa
tion generating data processing. Such models can be mathe-
matical or logical.
Handling of data error in mathematical models is well estab-
lished and utilizes variance propagation. For this a knowledge
of the Standard deviation of the variables, a mathematical
description of the processing model and a means to deter-
mine partial derivatives are required.
Handling of data error in logical models is not so well estab-
lished, but certainty statistics such as probability (as used in
'crisp' set theory) or certainty factors (as used in fuzzy' set
theory) may be used. It is possible to derive certainty factors
from Standard deviation, from field checks, or from other
forms of 'expertise', and these are outlined in the article.
Handling of model error in a GIS is also not well established,
and indeed for many geographic models Information on the
quality of the model may be difficult to obtain, however
some information on model quality is reported upon in this
paper.
This paper presents some fictional examples of data and
model quality storing and handling in a GIS, and also
presents a user interface which can prompt the GIS user to
'think about' and apply data and model quality. Also one
real example of agricultural suitability modelling essentially a
logical model) where both data and model quality are
processed, and the resulting quality information is graphically
represented (visualised), is given.
Data quality in GIS is a 'hot topic' now. It can be expected
that soon data quality handling tools will become Standard in
the GIS market place.
N.J.G. Gielen - Map reading in the Nineties: investigation of
the users of the Bosch Travelpilot
More than one year ago the first operational car navigation
System was introduced on the Dutch market. The Bosch
Travelpilot is an automatic navigation System which informs
the driver of the actual location of the car and also of the
direction in which the car should move in order to reach the
programmed destination. The Travelpilot uses a CD-ROM on
which nearly the entire road network of The Netherlands is
available in digital form. Seen in this way, the Travelpilot
may be considered as a kind of automatic map reading.
In this research report the experiences of the people who have
been using Travelpilot for a longer period are collected. This
provides important information for a market description, but
also for the determination of the contribution of such innova
tive Systems to the environmental issue of diminishing the to
tal distance driven by cars. The main result of this research
project is that the users of the Travelpilot realise extensive
savings in time as well as in distance.
F.J. Ormeling sr. R.P.G.A. Voskuil - Facsimile edition of
the Atlas of the Tropical Netherlands
Recently a facsimile edition of the Atlas van Tropisch Neder-
land was published, more than fifty years after the original
edition appeared in Batavia in 1938.
The first plans for a 'scientific' atlas of the Dutch East and
West Indies were made in 1906, but financial problems caused
repeated delays. The atlas was finally produced as a Co
operation between the Dutch Geographical Society, which
was responsible for preparing the maps in the Netherlands,
and the Topographical Survey in the Dutch East Indies, where
the maps were reproduced and printed. Although this System
of dividing the production was not ideal and caused delays,
the final result proved to be of high quality.
Nearly fifty percent of the Contents of the atlas consists of
topographic maps and the rest are thematic maps on a wide
ränge of subjects.
The atlas was soon sold out and in later years high prices
were paid for an antiquarian copy. The now published facsi
mile edition is limited to 1000 copies.
R. van der Schans - Instead of maps I: Digital models
Influenced by the new digital techniques the meaning of the
word 'map' seems to have shifted from a graphical Visu
al) representation to a digital description of parts of the
world. To prevent misunderstandings, the position is upheld
that it is necessary to make a fundamental division between
digital models of parts of the world (digital landscape models
or geographical databases) and digital models of maps (digi
tal cartographic models or cartographic databases). The first
type of models describes the world in a semantic way, in
terms of time, (two or three dimensional) geometry and
thematic attributes; the second type describes the Visual map
product as syntactic elements, i.e. as a set of coloured dots,
stripes and fields in the two dimensional Visual plane. The
consequences of this two-level view for cartographic terminol-
ogy, functions of the map and generalization are indicated.
Also, an outline of a theory for the transformation process
from digital landscape model to digital cartographic model is
given. Time, terrain geometry and thematic attributes can
each separately be mapped to all of the variables of the Visual
plane, viz. sequence, map geometry and colour. There can be
a loss in geometrical dimensions in the mapmaking transfor
mation, but also a gain in order to accommodate the themat
ic attributes.
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KT 1992.XVIII.1
