GEOGRAPHIC BASE FILE FOR
A SPATIALL ORIENTED
INFORMATION SYSTEM
Jan van Est Frans de Vroege
Delft, October 1982
(
j
The meaning and construction of
a geographic base file for a spatially
oriented information system
JAN
VAN
EST
FRANS DE VROEGE
Delft, October 1982
Bibliotheek TU Delft
Planologisch Studiecentrum TNO
CENTRE FOR )LANNING TNO ----~
1047
524
1
The meaning and construction of a geographic base file for a spatial -orientated information system.
Paper presented at the 9th European Symposium of Urban Data Management. Va 1 enci a, 27th - 30th October 1982.
Jan van Est Frans de Vroege
Planologisch Studiecentrum TNO P.O. Box 45
2600 AA Delft
Delft, October 1982 82/PS/378
Research Centre for Physical Planning TNO The Netherlands
2. The meaning of a map for a spatial-orientated information system 2.1. The computerized map
2.2. The function of segments of a geographic base file 2.3. The function of a geographic base file in a
spatial-orientated information system
3. The structure of a data file and a geoqraphic base file 3.1. Introduction
3.2. Structure of data files 3.3. Structure of a gbf
4. Methods of constructing a geographic base file 4.1. Introduction
4.2. The traditional method for constructing a gbf 4.3. The use of the gazetteer for constructing a gbf 4.4. The use of the VOR segment file for constructing 4.5. Conclusions
a gbf
5. Saladin, a spatial-orientated information system developed for use in
2 2 4 5 7 7 7 9 13 13 13 14 15
the Netherl ands lG
6. Literature references 22
Acknowledgements
This paper is an abridged version of a feasibility study of the Research Centre for Physical Planning TNO: " Thematic mapping for policy making". The study was commissioned by the Foundation Study Centre for Land Informa-tion on an initiative of the municipality of Rotterdam and sponsered by the Ministery of Internal Affairs and the Ministery of Housing and Physical Planning. The results and opinions presented here do not necessarily reflect the views of the Foundation, the municipilaty of Rotterdam, the Ministeries, nor those of TNO. The authors are responsible for the contents of and any errors in this paper. The authors thank the members of the Steering Commit-tee and the Project Group throughout the progress of the study for their assistence and guidance.
1. Introducti on
The concept of "a spatial-orientated infonnation system" refers to a special
kind of information system, in which the spatial dimension plays a crucial role. Several aspects can be distinguished:
a. The spatial dimension.
The locational reference of a data element like, for instance, a dwelling unit, a car park or an accident, is characterized by the fact that such data elements have a particular and fixed location, because they are
con-nected to the earth's surface. By means of suitable methods of locational
referencing, data elements can be localized and they can be properly
pro-cessed further as to derive the required information. b. Information supply.
The locational reference of data ~ements is meant to provide information
about various attributes of particular geographical units, e.g. quarters, neighbourhoods, routes and other arbitrary zonal subdivisions. Such geo-graphical units can also form a subset of other geographical zoning
sys-tems, e.g. census tracts, municipalities, etc .. In this hierarchical framework a dwelling unit is localized within astreet, linked to a par-ticular building block, which is part of a district, etc.
c. The (information) system.
With the aid of computerized infonnation systems, data files provide the input of the system and software or computer programs process these data
to derive the required information. The system is only able to process
data properly if two particular spatial referencing conditions are satis-fied. In addition, a systems approach is required to use the infonnation
system for a broad range of purposes, e.g. physical planning, transporta-tion, health care, etc ..
In a spatial-orientated information system the map or plan of the area con-cerned is stored in the computer and the locational reference of data makes it possible to know each locational interdependent relationships. That is to say, data elements can be spatially linked to addresses, coordinates, street-sides, blocks, etc. and all these geographical units can mutally be connected to each other. Not only the absolute or exact meaning of a loca-tion of data elements is of importance, but moreover the relative localoca-tion, i.e. spatial inter-linkages of data elements, are the driving force behind such an information system. The purposes of a spatial-orientated information
1. registration and description of address and non-address related data ele-ments, e.g. dwelling units and car parks respectively;
2. possibilities of linking various data files, i.e. there is a particular spatial key file with which several locational references can be ex -changed in order to link, to compare and to process data elements; 3. processing data for research, planning and policy making;
4. mapping of derived information (thematic mapping);
From the foregoing description it is apparent th at a special data structure and data processing operation is required. This necessity stems from the direct use of a map with geographical units and locational references. To be able to make use of a map within the information system, computerized know-ledge of the map or streetplan is necessary.
In this paper the special meaning of the spatial dimension of a spatial-orientated information system will be discussed. In the second section the meaning of a map for such a system will be considered and the necessary con-dions will be given. It turns out that a spatial scematized structure of the transport infrastructure, i.e. segmented geographic base file, can be con-structed in order to form the base of the information system. In the third
'section the construction itself will be outlined. In the Netherlands, many municipalities already have computerized files, showing street-side charac-teristics, which in fact are part of a segmented geographic base file. The consequences of their existence for construction the files concerned were studied in a feasibility study for the city of Rotterdam (Van Est and De Vroege, 1982). A summerized version of this will be presented in section four. In section five the framework of a spatial-orientated information sys -tem will be outlined. The paper will be concluded with some findings from
the Rotterdam study.
2. The meaning of a map for a spatial-orientated information system
A map or plan is an essential tool for registration, processing and repr esen-taion or mapping of spatial-orientated data and information. To computerize such an information system, it is necessary to also store the map in the com-puter. A map is in fact an analogue, i.e. similar but simplified, representa-tion of reality. By storing this map in the computer, the map is converted to a so called digital topographical file, that can be read and recognized
by a computer only. By means of a plotting device, the computer can again make analogue maps from the digital file.
A large scale digital topographical file is normally built up out of lines (i.e. vectors), with which only the absolute location of elements, repre-sented by these lines, are known. The lines of such topographical files are used to describe areal elements. However, the mutual and interdependent re-lationships between the elements, which is so crucial for data processing, is not known explicitely.
To determine relative locations and distances, two questions have to be ans-wered. The first question is how to determine contiguous areas and zones
(i .e. the topological structure). The second question is how to apply the concept of "distance". Both questions can be answered by using modern meth-ods of geocoding.
The lines of the earlier mentioned topographical maps are, or can be thought of as being built up out of segments. The segments can be defined direc-tionally with left and right hand sides, referring to areal elements of the segment respectively. This is the basis of the two-sided line method defin-ning areal elements, such as polygons. It is now also possible to identify contiguous zones. In this way the first problem is solved. The di stance con-cept can, however, not yet be applied because the spatial structure itself, e.g. astreet, can not be identified explicitely. It follows th at the appli-cation of the two-sided line method is a necessary, but not sufficient, con-dition.
On a large cale map many lines are used to describe all attributes of a street. The street itself is not uniquely defined, which is necessary for ap-plication of the distance concept. The whole transport infrastructure, i.e. roads, waterways, railways, etc. ca.n be defined and digitized according to the two-s i ded 1 i ne or segment method through the road-centre 1 i nes, so that the infrastructure is reduced to a network of links or segments. It means that roads and the like are scematically represented by the road-centre lines. Intersections in the network are defined by points or nodes and their numbers, while the segments are defined by the connections between these nodes. Areas along the segments can be defined by a closed combination of segments. The network representation is a sufficient condition for apply-ing the di stance concept: the segment can be used for route-findapply-ing.
In conclusion it can be stated that application of the two-sided line method on a single-sided line representation of the infrastructure network is a
necessary and sufficient condition. The result is a simplified image of the spatial structure, which is called a (segmented) geographic base file (gbf). There are differences between digital files as a consequence of following the applied digitising method. The most significant difference between
digi-tal topographical files and geographic base files is the identification of intersections. There is no mutual interdependency of features within
topo-graphical files and so the system is intrinsically not able to recognize if
"A" and "B" street have a common and indentifiable node, representing the
intersection. For a gbf it is an essential feature to find such nodes, from
which topological relationships as well as impedance or distance matrices
can be derived.
The upgrading of large scale maps to a gbf has important consequences, as
mutual interdependent relationships between spatially separate objects, e.g.
addresses of houses and bus stops, can now be established. This is done by
linking these objects, as point locations, to the adjacent segments. It
really means that every data file, with an address or semi-address locatio-nal reference, can be linked to a segment file.
The linkage of a data element to a segment has two results. The first one
is th at these elements can be identified along a segment side. Without
coor-dinates of those elements, it is possible to locate them proportionally. But
with point-coordinates references a spatially more exact assignment is pos-sible. From an administrative point of view, it is now possible to locate data and information along segment sides, and because the gbf is
computeri-zed thematic mapping can be done automatically. In this way all kinds of classifications of shops, road accidents', etc. can be visualized on automa-tically prepared maps, which saves laborious efforts in producing so called
pin maps or dot maps by hand, The second result of the segment method is
that it is no longer necessary to process data elements individually, as
the segments associated with the objects concerned can be used instead, reducing work significantly. This argument holds for all kind of aggregation
procedures, such as the definition and determining of new zoning systems, and
for the assignment of data files involved.
When the two results are considered from a methodological point of view, a
relevant distinction is to be made between the information source, i.e. the
process the data elements involved. This implies that point locational refe-rences are suspended,as it were, from the segments. It is the simultaneous action of various data files, as an information source, and segments, as in-formation carriers which constitutes a really spatial-orientated inin-formation system (Van Est and De Vroege, 1982). The revolutionary idea of such a
sys-tem is the independency of the data files and their structure, because
seg-ments are now processing the data. As long as there is a common locational reference in the data file and the geographic base file, this file will func-tion as a survey file, whilst as a geographical key it takes care of
compa-rability and transferability of data (Van Est and De Vroege, 1981).
From an organisational point of view this kind of system promotes decentra-lisation on the one hand, because governmental offices and public agencies can keep and use their own decentralized data files, whilst on the other hand they can communicate with each other by making use of a centralized geographic base file.
Thus, digitizing a large scale map according to the upgraded segment method provides a base for a spatial-orientated information system. There are several reasons for choosing the network as base of an information system: 1. the spatial structure represented on a map has to be similar with reality,
both topographically and topologically;
2. a network structure is able to form all kinds of different zoning sys-tems (e.g. ) centroids, polygcns, grids, etc .. All arbitrary or admini-strative zoning systems can be derived and data elements can be assigned to the zones concerned by making use of the network;
3. a network structure is a necessary tool in dealing with research and plan-ning problems, such as:
a. structure planning (e.g. accessibility and catchment analysis); b. spatial and physical planning;
c. transportation planning.
4. a network structure is able to deal effectively with very complexe spa-tial structures;
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The geographic base file serves as an overview and key file in a spatial-orientated information system. Because of different locational references it is possible to exchange and to link various data elements. The linking can be done through four different locational references:
- addresses,
- nodes or segments,
- coordinates,
- areas or zones.
Figure 1. The relationships of data files and gbf within a
spatial-orienta-ted information system: "the spider-leg".
population housing industry em 10 ment street attributes capacity data traffic data topography centroids boundaries networks census tracks school districts catchment areas zonal subdivision
By these characteristic of a gbf the information system is like a "spider
with different legs". Several data files can be linked to these legs, as
is shown in figure 1. Thus, the information system is able to perform a
number of applications of these data files. Examples are:
a. registration of address and semi address orientated data element and
their representation on thematic maps;
b. processing, aggregation and assignment of administrative and
statisti-cal data for arbitrary zonal subdivisions and their representation on
thematic maps;
c. defining and setting out new zonal subdivisions according to various
criteria of homogeneity, accessibility, distance, etc.;
d. determination of catchment areas for schools, shops, bus stops, etc.;
e. calculation of optimal locations of public facilities such as fire bri-gade stations and sporting halls.
3. The structure of a data file and geographic base file
3.1. Introduction
In the previous section it has been shown that a spatial-orientated
infor-mation system is essentially based on: 1. a geographic base file (gbf), and
2. various data files.
Linking one or more data files to the gbf makes it possible to derive infor-mation from those files. Also since the feasibility study in Rotterdam it is possible to present the resulting information on thematic maps automatically. Conditions with respect to locational references have to be satisfied to en-able the linkage of both types of files. In this section these conditions will be discussed. Firstly, the requirements for ordinary data files will be dealt with. Then the conditions for the gbf will be considered.
3.2. Structure ---of data file
In general a data file consists of a collection of attributes of a number of subjects. An example is a housing file with a number of a attributes for each house. These administrative files can be set up either by hand or they can be computerized. With the increasing need for proper planning and policy information many of such administrative files has been computerized already.
This computerization of data sources is a first and necessary condition for the application of an information system.
A second condition relates to the access cf a data file as far as the spatial dimension is concerned. A locational reference is necessary if data elements have a spatial meaning in th at they are attached to the earth's surface, for instance a residential unit. From the Rotterdam feasibility study it appears th at the following locational references occur of ten:
- streetname and building number;
- streetcode and building number;
- streetname or code and semi-address number;
- streetside; - street;
- areal codes, likes quarters and districts;
- point-coordinates; - grid-numbers.
Whatever the structure and format of a data file, as long as at least one
of these locational references is to be found in the data file as well as in the gbf, a link between the two files can be made. Therefore, it can be stated that it is a necessary and sufficient condition for a computerized data file to be used for spatial processing if at least one of the mentioned
locational references is used.
At this stage some notes about the foregoing condition should be made. A
first note might be about the spatial scale level, to which data can be
re-ferred. For instance, a residential unit can be locational referenced by
its address or by its district. A data file which is referenced by addres-ses can always be aggregated to district or any other zoning system. The
other way round, that is to say to disaggregate districts into addresses, is not possible without consultation of the original address-information.
It means th at if a proper aggregation procedure has been used, a consistent
data capturing along the "micro-macro data line" is possible. This
versa-tility condition is called the "common spatial-orientated language (COSOL) concept (Van Est and Smit, 1980). It follows that a data file must always
be presented through to the lowest level.
A second note might be made with respect to cadastral parcels, because they
do not yet have an explicit address-entry. Data files with standardized
writing of ordinary addresses can be linked to a gbf without problems. To locate a parcel spatially extra locational information is needed. By means of application of a conversion.table which relates
parcelnumber-address - point coordinates - segment (a so cal led PAPS-system), cadastral
data can be linked to a gbf. The PAPS-system enables the exchange of
information between three groups of land information systems:
parcel-orientated and address-parcel-orientated and map-parcel-orientated systems (Polman,
1981). At this moment the land registry office, "Cadastre", in the
Netherlands is looking for a method and procedure to establish the
relationship between parcels, addresses and coordinate references. In this
context it might be considered that it is important to study how to link
parcels without any address, as well as parcels not situated along a
seg-ment, to a gbf. A third note might refer to data files which do not have
like car parks and road accidents. A semi-address reference is required which can be ad hoc made in differnt ways and which can be added to the gbf if necessary. In that case all ordinary possibilities for address orientated applications can be used. A fourth note is related to point coordinate referencing. In various cities point coordinates are used to locate premises. This type of locational referencing is very hel p-ful in locating objects along segment sides properly and also for loca-ting objects within areas. It must be stated, however, that coordinate references play a minor role in an information item itself, because of the administrative processing operations on data; coordinate references are especially important and even necessary for producing thematic maps. A last note refers to the General Base Register (GBR) of addresses in the Netherlands, which is ueveloped and set up by the National Agency for Physical Planning (RPD). In the GBR postcodes, neighbourhoods (i.e. CBS-zoning divisions) and grids (i .e. 500 meter squares) have been assigned to all known addresses of the housing stock; the work concerning business addresses is in preparation. At this moment the RPD is interested in the possibilities of an exchange between post-codes and segments or street-sides. It is a question if post-codes can be used as a segment system? Research on this topic is in progress.
In the previous section locational references were mentioned, which were necessary either for location of objects in data-files or for applications. These data files can only be dealt with in a spatial-orientated information system if the gbf also contains the mentioned locatianal references. The questions now are how the gbf is structured and if these references are part of a gbf.
The geographic base file is the base of the system and represents the loca -tional structure in both an absolute and a relative sense. This is the reason for setting conditions on necessary components of such a file. In general , a gbf describes the named street pattern, the transport infra-structure by means of nodes and segments. The number of segments needed for railways and waterways is less th en one percent of the total number of segments.
For each part of astreet between two intersections one segment is used to describe the streetpattern and the areas along side that street. It is
defined by:
a. the geocode part, with nodes "from" and "to", possibly extended with intermediate points for curve fitting of streets, and with
arealor block designation for the identification of both, left
and right, sides of a segment;
b. the metric part, with which nodes are represented by their coordi -nate references;
c. the nominal part, naming that part of astreet by its name and code,
and with addition of the range of housenumbers for both sides of that part;
d. the attribute part, with the encoding of administrative areal
subdi-visions and segment-class for classification purposes. The segment definition leads to the following components: 1. node numbers,
2. block numbers
3. coordinates,
4. streetnames, 5. segment number,
6. range of address numbers,
7. areal codes, 8. segment class.
With these components (see figure 2) a geographic base is defined. Deleting one or more of these components can lead t~:
- hampering applications of the information system;
- degeneration of the gbf;
extra software facilities trying to overcome the missing components; - restricted insight in the results of the system.
For a gbf it is also necessary that the whole network be recorded, which means that access roads and dual carriage ways should recorded separately.
Deleting parts of the network will bring about difficulties, e.g.: - addresses can not be linked to segments anymore;
- spatial objects (e.g. car parks and lamp-posts) and occurrences (e.g. accidents) can not be localized anymore;
- land use can be indicated ambiguously;
- functional registrations, for instance related to public transport can
not be made.
J
\
1
i
J
l
Fig. 2 Representation of a segment with geographic characteristics on the two-sided line method.
From node To node
~
137-I
Co-ordinates from node Co-ordinates to node Road name
Type of road Left hand b loek
I
55
218
32
L
Mainstreet
-128
1r-
19-
7
-2-5-23---'11
I
137 128x
137 ' Y137 X128 ' Y128 Mainstreet Residental street 32Addresses on the left side Right hand block
218-282
25
Addresses on right side Left hand zone
Right hand zone Code for streetwidth Segment number 197-231 55 55 4 4711030
It follows that each part and side of astreet has to be identified by the segment file. Only in that case a one-to-one correspondence with the spatial structure can be obtained.
When the locational references of various data sourees are compared with the components of the gbf, it appears (see table 1) that all locational
references are in the gbf, but for one exception; data elements with no address entry. As has been mentioned in the previous section, in that case a semi-address entry has to be constructed and addedd to the gbf. If thi s entrv i snot very often used, it can be better kept on a sepera te fil e. From table 1 it also appears that coordinates and segment class are not mentioned. It is evident that the latter is not mentioned, because such classification is only used for a better representation of the road
Table 1 Representation of relationships between locational references and components of a gbf
I~:"
address semi street seg- inter blockgbf referen address side ment section
s~
components nodes x x blocks x x I street x x x x x name segment (x) (x) x x x number house x (x) x x numbers areal x codes x x area x xstructure on thematic maps and for path finding (shortest routes) in a network. Coordinates have a more indirect function. They are added for absolute loca-tional refercing on thematic maps and for some geometrical operations. Until now the necessary components of a gbf have been considered. It is, how-ever, possible that other spatial location or areal references are desired. For instance cycle-tracks can be sufficiently important to serve as basic data. In this case a special cycle network can be constructed and added, if necessary, as a separate file to the gbf. Generally it can be stated that basic geographical files, incidentally used, should be kept seperate from the gbf - just like the semi-address files - and that such files can be added to the gbf, when they are needed for special purposes.
4. Methods of constructing a geographic base file
4.1. Introduction
There are several ways of constructing a geographic base file. In this sec-tion three particular methods will be discussed. The first method is tradi-tional; it starts from scratch. The second one takes into account the
exis-tence of a computerized street index, containing ranges of house numbers
between intersections, further on to be named as a gazetteer. Such gazet-teers have now been built up for almost five hunderd minicipalities, out of a total of eight hunderd municipalities in the Netherlands. It means that a great deal of a gbf already exist.
A third method refers to the existence of segment files of the Department of Registration on Road Accidents (VaR) in the Netherlands. Since 1975 this de-partment of the Ministery of Transport takes care of the central processing of these data. They are now digitizing the whole road network of the Nether-lands according to the segment method. With a few adaptations, such as block numbers, these segment files can be converted into geographic base files for a multi-purpose functioning. When the segment files of the VaR are used by local authorities they can obtain a gbf very simply.
In the feasibility study for Rotterdam the mentioned methods have been con
-sidered in detail. Here only an abridged version will be presented.
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A geographic base file contains a number of segments, which are the basic units of a gbf and due to that fact, they are also the information carriers of a gbf. The four main parts, describing a segment, have to coded and pro-cessed.
According to the traditional method, the following stages can be distin-guished:
a. Construction of the network
On a transparant paper, laid over a streetnamed map, all nodes (i .e. in
-tersections) and their connections are indicated. Node numbers and block
numbers, and if desired also route numbers and special attributes of the network, are designated.
b. Digitizing the network
The network information of the overlay is digitized and stored into a computer. For small areas the digitizing can be done by hand or otherwise
with the help of a digitizer. c. Geometric testing
An image of the digitizing network is plotted and checked. The DIME (Dual
Independent Mapping Encoding) software can be used to check if both,
nodes and segments, built up to a complete network file. This step is
indispensible because it is the only way to check the topological
struc-ture of a gbf automatically. d. Nominalizing the network
The created segment file is now related to reference data by adding streetnames, codes, ranges of housenumbers and administrative areal codes. e. Administrative checking
A check is made to see if reference data are complete. A administrative test has been developed to see if streetnames and ranges of housenumbers are correct.
f. Documentation of the gbf
When the gbf has been checked and corrected, the gbf has to be described
properly and documented for future updates and applications.
Above a sketch of processing the various stages for creating a geographic
base file has been presented. From the feasibility study in Rotterdam it
was learned that the cost involved in creating a gbf for Rotterdam, based on
experiencing in three test areas in Rotterdam, is about 0.2 guilders per
inhabitant or ten guilders per segment.
In Rotterdam, as well as in many other municipalities, the existence of the gazetteer enables a gof to constructed in another way, because in 80% of the
cases the nominal parts of the segments were ready. The remaining 20%
re-fers to double sides of dual carriage ways and access roads which do not
have address numbers. So in principle the nominal part of the segements con-cerned has already been determined, which means a saving in time and costs
in creating a gbf.
The gazetteer and the traditionally pre~ared geocode part are linked bv
ad-ding node numbers to the gazetteer records. This method can be aoplied in two different ways, either by hand, as automatically by using address
coor-dinates. The hand method is straight forward and may reduce cost b.y about 3G%.
In Rotterdam, a large scale topographical map has been digitized in the ARTOL
result of this project all premises have point-coordinates. These coordi-nates can now be used to link the nominal part (i .e. addresses) to the
geo-code part of a segment. This procedure can be computerized. If Rotterdam
pays half the program development cost of that procedure, the cost of
crea-ting a gbf may be reduced with 43%.
The last alternative method for constructing a gbf is to make use of the VOR segment file. When this file is available for Rotterdam free of charge, a great deal of the gbf will be ready. What remains to be done is:
- a test with which the segment file and the gazetteer are co~pared to ensure that all streets and segments are present;
- a conversion table for streetcodes, because the VOR uses his own
street-codes, which are not compatible with those of the gazetteer. A similar
in-compatibility occurs in the case of streetnames;
- an adaptation and updating v/here necessary.
The convertion table is simply to make, as is the test. Compared with the traditional method (starting from scratch, the availability of the VOR seg-ment file will save more than 50% of the original cost.
4.5. çQ~~!~~!Q~~
Considering the cost of each method a first conclusion is th at the availa-bility of the VOR-segmentfile, which is free of charge, provides the cheap-est and simplest method of creating a gbf. A saving of more than 50% can be achieved, compared with the traditional method.
A further observation is that the gazetteer is alocal street index, in ~ene
ral use and therefore it is worthwhile to generalise the conclusion to all those municipalities having a gazetteer.
A third conclusion is that the VOR segment files are using streetnames and
streetcodes, which are different from localones. Therefore to enlarge the num-ber of applications it is recommended to extend the segment file with local
street references. Apart form the application issue, the enlargement is important in order to facilitate future updating of the segment files. A last conclusion is that if the VOR segment files could be extended with some extra attributes, such as blocknumbers of the gazetteer, it can make this file function as the geograp~ic base file of a spatial-orientated in-formation system.
5. SALADIN, a spatial-orientated information system, developed for use in the Netherlands
The basic idea of a spatial-orientated information system is that of appl y-ing the segment method on a scematic spatial structure. This method was developed by the U.S. Bureau of the Census (1970) in the late sixties and is now known as the DIME-concept. The first application was the U.S. cen-sus in 1970; by now it is also applied at metropolitan levels in the Uni-ted States of America, the Scandinavien countries, England, Germany, Cana-da, etc ..
The DIME-concept is, in fact, a method and not an information system; DIME is meant for creating, testing and updating geographic base files. Because of its simplicity efficiency and suitability for applications, it appears to be a good base for an information system. In this respect the following segment-based information systems in various countries can be mentioned: - NIMS, Sweden (Selander, 1978),
- TRAMS, England (Perrett, 1976), - DATUM, Germany (Datum, 1977),
- GRDSR, Canada (Statistics Canada, 1974), - RGU, France (Flour, 1978)
- ODYSSEY, United Stated (Dutton, 1979), - GIMMS, Scotland (Waugh, 1974).
In the late seventies the Research Centre for Physical Planning (PSC)-TNO started to develop a spatial-orientated information system that could be suitable for application in the Netherlands. Because of International con-tacts, such as SORSA (Spatial Orientated Referencing Systems Association) and IANU (International Association of NIMS Users), it was not necessary for the PSC to reinvent the wheel. Therefore, in developing on information system for the Netherlands, use has been made of some of the mentioned soft-ware packDges. Special mention schould be made here of the NIMS-system, de-veloped as a planning instrument in the Scandinavian countries. Important modules of the NIMS-system are twelve programs for defining and setting out new zoning systems and for aggregating data accordingly, and programs for the spatial allocation of public facilities.
Relevant parts from various packages were selected, and where necessary, adjusted to the situation in the Netherlands. So far, special attention has been given to the registration and presentation of address and semi-address
orientated data elements or information. This line of development was chosen, rather than the application of programs for optimll locations
and other planning problems, because there was at first, an apparent need for the presentation of data and statistics on thematic maps. The hand-made pin or dot maps are time consuming, whilst computerized map-ping - according to the segment method - can be performed very cheaply and rapidly. For presentation of the information on cartog.raphic (i .e. automa-tically prepared thematic) maps, a special "double line" system has been developed, in which the streedwidth is used for a better presentation of the spatial structure of the area concerned. Using these programs, the Research Centre has developed a spatial-orientated information system for the Netherlands, named the SALADIN (~patial ~nalysis and ~utomatic
Data Processing Information) system.
The Research Centre started with the creation of a geographic base file for the city of Eindhoven, because data were available for demonstration. In the middle of 1981 a gbf for the inner-city area of Amsterdam was com-pleted. Within the framework of the feasibility studies for the cities of Amsterdam and Rotterdam various tests were made.
In order to show some possibilities of thematic mapping, a few examples will be presented. First of all, an example of a gbf with node numbers of the city of Eindhoven, is presented in figure.3. For thematic maps, many sy m-bols for classifying data for arbitrary zones or routes can be shown. For instance in figure 4 , an example of a bus route and its stops is shown. From the point of view of analysis, catchment areas for the bus stops shoul d then be determi ned i norder to s tudy access i bil ity. Next an e~~mp 1 e involving shopping is presented in figure 5, where a classification of shops into food and non-food categories is shown. With a suitable data file a more detailed classification can be used as input, for a shopping model to
esti-mate money flows of shopping purchases in order to analyse impacts of planning decisions. Another example is a presentation of business locations according to the CBS-classification, see figure 6. From the data the number of working people, both full-time and part-time, at each segment side can be derived and presented on a thematic map, as is shown in figure 7. A last example is a thematic map of housing density per person in a arbitrary zoning system. In figure 8 only a very rough classification is shown; it is a map made on a printer to show the contrast with a plotted map. With the GIMMS-program more detailed information per zone, i.e. parted apple-pies can be shown.
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As a conclusion, it can be stated that a spatial-orientated information
system is a very useful instrument for a multi-purpose presentation of information on thematic maps and processing data for various impact ana-lysis problems. Description, anaana-lysis and evaluation in planning processes require structural information (Nijkamp, 1982). A spatial-orientated
information system renders the required information in a short period of time and at reasonable cost for research, planning and policy-making.
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segment. N ofigure 8. Thematic map of housing density per person for an arbitrary
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? 4 3 5 1000001 18.1181181 1111111 1000001 IUltfHll 1.11111 1000001 I 11 1'1 IIIH! I 1.11111 laOonOl 1111111 11 . . 1116. Literature references
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