THE TOPOGRAPHIC DATA SYSTEM IN SLOVENIA
COLECTION AND ACQUISITION OF DATABASES
Tomaž Petek and Marin Smodiš
Surveying and Mapping Authority of the Republic of Slovenia
Zemljemerska ulica 12, SI-1000 Ljubljana, Slovenia
Tel: ++386 61 178 48 00, Fax: ++386 61 178 48 34
E-mail: tomaz.petek@gu.sigov.mail.si
Abstract
The paper will present the hystory and curent situation of national topographic databases in the Republic of Slovenia. There will be explaned methods and experience in colection and acquisition of databases and other products in digital form wich are producet by our authority. In the past year a considerable part of the data for Slovenia was acquired in digital form. Major attention is directed towards the creation of topographical database with a precision and detail scale of 1:25000. Some of the elements of this area have already been compiled for the entire teritory of Slovenia. I am attend to presentation the database structure, the methods of acquisition and quality of data. In the second part I recommend to describe examples of using this database and its updating.
Keywords: topographic and cartographic system, digital topographic data
INTRODUCTION
The national cartographic system covers the territory of the Republic of Slovenia and parts of its neighbouring countries, wherever that is necessary for filling the system maps. The topographic and cartographic system of Slovenia is the official national recording system for all Slovenian analogue and digital topographic and cartographic data and material. It includes maps and digital bases of spatial data of scale and precision levels between 1:5 000 and 1:2 000 000, and data from other bases connected with topography. The supervisor of the topographic and cartographic system is the Surveying and Mapping Authority of the Republic of Slovenia (SMA) of the Ministry of the Environment and Physical Planning, which provides continuous financing and supervision from the national budget. The Slovenian topographic and cartographic system is, in content, similar to other European systems.
Slovenia possesses large quantities of cartographic material in various scales in analogue form, which are, in terms of their storage medium, of limited use. In order to avoid automated digitization of this material, the SMA has begun restructuring the digitization of geodetic records with a series of development and applied projects. Using modern technologies and methods it is striving to adjust to the needs of users and to its own capacities, with a trend towards establishing comprehensive topographic databases within a reasonable time period and with realistic financial assets. The analogue material is being converted into digital form, with standardized quality control. The emerging topographic and cartographic system will record databases of the principal data of national importance by a method which will allow its distribution in the form of standardized products in graphic, numeric and classic cartographic form. Limited by available financial and staff capacities the SMA is building gradually, with regard to the immediate needs of users.
HISTORY
In the past, the topographic and cartographic system for Slovenia was analogue, and since 1993 has been systematically converted to a modern digital topographic and cartographic system. The process was initiated immediately after Slovenian independence. Prior to that part of the cartographic system was in the hands of the former Yugoslav military, thus leaving much of the cartographic material in Belgrade. Since we have not managed to recover all the material necessary for upgrading the system, after the break-up of Yugoslavia, we are now working on it wherever empty areas occur. Between 1992 and 1994, the SMA began conducting a series of development research projects with the primary aim of renewing and modernizing the national topographic and cartographic system.
Thus the project of creating the first Slovenian national topographic map on a scale of 1:25 000 began. Its conception stretches back to 1947, when the bases for the map were established. Slovenia managed to obtain the publisher’s originals of these maps from the years 1985-1986 from the Military Geographical Institute of Belgrade before the declaration of independence.
The project of creating scanned map originals of the reproduction originals of all larger scale and small scale maps for Slovenia was initiated in 1993 as part of the digitization of geodetic records.
Digitization of the individual contents of various topographic maps was carried out. The first databases were converted from national maps by various contractors appointed by the SMA. Standards were set, based on current knowledge, which mainly include the content and structure of the bases, exchange formats, the manner of compilation and quality.
The SMA’s aim was to employ modern technology and methods in an effort to adjust to the needs of users.
CARTOGRAPHIC MATERIAL
Currently Slovenia has larger scale maps on a scale of 1:5 000 and 1:10 000. A national topographic map on a scale of 1:25 000, a topographic map on a scale of 1:50 000 and small scale maps on the scales of 1:250 000, 1:400 000. 1:750 000, 1:1 000 000 and 1:1 500 000.
Basic topographic maps 1:5 000 and 1:10 000
DIGITAL DATABASES
Scanned map originals
Scanned map originals have been made from all the reproduction originals of the basic topographic maps, scales 1:5 000, 1:10 000, topographic maps, scales 1:25 000 and 1:50 000 and small scale maps of Slovenia, scales 1:250 000, 1:400 000 and 1:750 000, for the entire territory of Slovenia. On all the scanned map originals only the contents within the frame of the page were scanned, making further use easier, especially in combining pages for system maps. The data is scanned with a resolution of 300 dpi, the contents of individual layers depends on existing reproduction originals of the maps. Each scanned original is spatially referenced and recorded in its database with name, date of conversion, scanning operator and data owner. All the pages of the publisher’s originals, which result from updated classic topographic maps are immediately scanned, thus ensuring maintenance of the database of scanned map originals.
Digital topographic database
The project of the methodological and technological solution for establishing and maintenance of a digital topographic database (TOPO5) provided the instructions for its establishing and maintenance. The base comprised a test area. The sources for ackuisition will be aerial photography in scale 1:17 000 and some other sources, for example digital ortophoto plans and scanned publisher’s originals of the basic topographic maps on the scales of 1:5 000 and 1:10 000.
A part from their use in geodesy (providing a topographic and topologically simple base in vector form and at the same time a cartographic base for drawing maps) this data is intended primarily for use in planning on a local level (roads, use and potential uses of an area, hydrography, forestry, etc.). So far only a test area has been included, but future plans have been made to establish a comprehensive system and to manage and maintain such a database.
Records of geographical names
Parallel to the renewal of the maps of various scales (1:5 000, 1:10 000, 1:25 000) the SMA is creating a Record of Geographical Names (RGN). On the basis of the project for preparing the technological basis for establishing RGN, the instructions for establishing, supervision and maintenance were also defined. The primary purpose of geographical names is orientation in an area. Apart from its usefulness in everyday life, this aim is even more strongly expressed in the use of geographical names on maps, publications, atlases and in the use of digitized data in various GIS, postal services, etc. Positioning geographical names depends on relative positions with regard to other contents, and therefore cannot be positioned exactly. Control of the positioners on publisher’s originals of geographical names assure the graphic accuracy of the copy to within ± 0.2 mm * scale.
Digital ortophoto plans and maps
Digital partial stereorestitutions of maps are digitized aerial photographs transformed into the national coordinate system with the inclusion of a digital relief model. They are drawn in the scale 1:5 000. The sources for creating the partial stereorestitutions are aerial photographs in various scales of recording: for basic topographic maps on the scale of 1:5 000 the recording scale is 1:17 500, for basic topographic plans on a scale of 1:10 000 the recording scale is 1:30 000, The guidelines for standards and practical drawing of partial stereorestitutions of maps were determined within the project. By copying onto paper or film it is possible to get a picture - partial stereorestitution at any chosen scale. The resolution of the data for the partial stereorestitution of a map on a scale of 1:5 000 (DOF5) is 0,5m and the positional precision is 1,5m. The data are in raster form and are intended as a background for various computer applications as well as for compiling various contents.
Digital terain model
The model of the Earth’s surface on the territory of Slovenia, defined by a square grid of points distanced 100m apart is called the Digital Model Relief (DMR). For each point the altitude above sea level is determined, which enables us to generate the DMR. The sources for data entries were basic topographic maps on the scales of 1:5 000 and 1: 10 000. DMR data facilitates various analyses, photography, etc. DMR has been made for the territory within Slovenia, while for the territory covered by the small scale map on the scale 1:250 000 it is still being drawn using corresponding data from neighbouring countries. Another project is underway, for improving the quality and density of the digital model relief. In last few years is produced new Digital terain model, geathered in production of digital ortophoto plans. Model is degfined by a square grid of points distanced 25 meters. This model is available for about 30% of territory of Slovenia
Register of spatial units
The Register of Spatial Units (RSU) is a database which includes digitized borders of spatial units with their centroids and descriptive data about interdependencies and hierarchy. In the RSU we keep data on the basic and additional spatial units. Basic spatial units are those which homogeneously cover the entire territory of the country. These units are the spatial section, statistical section, settlement, municipality, cadastral municipality, SMA office, administrative unit and country, house number and street name. Additional spatial units can cover the territory of the whole country or individual comprehensive regions. These are: street, regional SMA office, local community, rural community, city district, electoral area and a number of others. RSU is organized as a central base, which is kept and maintained at one location, but access to the data is possible from all regional SMA offices.
Generalized cartographic database
We wish to devote some special attention to the Generalized Topographic Base (GKB25), its use and future development. With a project started in 1994, the SMA managed to include the entire territory of Slovenia for four thematic groups of GKB25. We have chosen this title because the data was derived from scanned map originals of the systemic topographic maps, in which individual elements were more or less generalized. The data compiled in this base is intended to serve several purposes: drawing digital maps on the scale of about 1:50 000, with generalization also on smaller scales, analysis and investigations in a GIS environment, and in combined use. Because of its structure and content it can be included among elements of a topographic base of medium precision. So far elements of the following thematic groups have been digitized:
1) Roads
Roads include the axes of all road sections, shown on a topographic map on the scale of 1:25 000 (roads with all road structures, i.e. bridge, tunnel, etc.). For roads, identification axes have been digitized as one line, for motorways, the axes of both roadways have been included. Every line includes descriptive data on the type of road and road structure. Besides general descriptions, each section is linked to data from the Directorate of Public Roads, compiled on the basis of maps on the scale of 1:50 000. After all 201 pages were completed, control identifications were conducted, as well as vectorisation and visual control of overlapping, topological correctness and comprehensiveness.
2) Hydrography
The hydrographic content includes all the axes of waterways with descriptive data of the type, name, width and direction of each section of the waterway in the hydrographic network. Structures on the waterways constitute the point layer, while the descriptive part shows the type of structure on the water, such as dam, waterfall, source, and so on. Flat structures on the water include descriptive data about the type of water surface and constitute the polygon layer.
3) Contour Lines
Contour lines are included as shown in the source, and form the line layer of the relief. Main and basic as well as support lines show data about the altitude above sea level, included as descriptive data, corresponding with the coding defined in structural standards.
4) Railways
Elements of the thematic group railways are the axes of railway lines, station structures and other structures on the railway. Besides their spatial positions they also include data on the type of railway line, electrification and the type of railway structure on the railway, and the name of the station structure.
In addition to general descriptions (source of data, supervisor of the data - organisation, supervisor of the data - contact person, compilation - organisation, date of data compilation) each element also includes special descriptions determined with the help of a cartographic key.
Precision
Positional precision of all layers are the precisions of scanned publisher’s originals of topographic maps on a scale of 1:25 000. We estimate this to be between ±5 and 10 metres. Altitude precision is estimated between ±10 and 20 metres.
Drawing - scope
The entire compilation and joining of the sections was conducted by a mapping and surveying organization through a contract with MS. The work was assigned to contractors after a public bid published in the Official Gazette of the Republic of Slovenia. For the entire compilation and establishing, the SMA has so far allocated slightly less than DM 1 million.
Standards
During the project for establishing and compiling data for a base of medium precision, internal protocols and methodological standards were formed, which were confirmed by the SMA. The entire data compilation was conducted according to these standards.
MAINTENANCE AND UPGRADING
Most users exhibited a need for a several yearly cycle of maintaining data at the base. In most cases these are national institutions, which need digital data from the GKB25 database for planning on a national level, and find the given updating schedule sufficient. In the first phases, the maintenance project mainly involved entries of changes after updating classic topographic maps and their reproduction originals. During regular maintenance the operations of scanning and vectorisation of changes entered into the base were repeated. After the entry of the changes the topology was constructed and the base was again available to users. For 1997, the SMA is preparing a project for establishing a system of maintenance of GKB25 from original sources, such as aerial photography and data from other supervision bases.
USES OF GKB25
The base is intended for supervisors of databases for the purposes of geodesy (national topographic base, national topographic map) and to provide other users of databases an access to the geo-information infrastructure.
The topological structure of the generalized cartographic base is suitable for use in a GIS environment, or as entry data for cartographic bases of smaller scales. All the elements are compiled according to the rules for constructing GIS and can act as the basic framework for individual applications, and offer us a good starting point from which each user can define his spatial data. Here we encounter a discrepancy between the demands of users and the means and capacities available. The base presented here is a sound compromise, which can be effectively used in many areas. We are pointing out here the usefulness of GKB25 together with layers of scanned map originals, digitized partial stereorestitution, digital cadaster maps and the data from the register of spatial units kept and maintained by the SMA. With this we have satisfied the immediate needs for spatial data in digital form. Future development should be directed towards improving the quality of compiled data.
CONCLUSION
In as much as this paper has succeeded in presenting the basis of the topographic and cartographic system in the Republic of Slovenia and has illustrated the efforts and activities of the SMA in constructing a modern system of digital topographic bases and larger scale maps, its purpose has been achieved. By establishing a generalized cartographic base compiled from a source on the scale of 1:25 000 the SMA strived to provide the largest possible circle of users with an adequate solution, within a reasonable time period and with relatively limited financial assets, in a transition towards establishing a comprehensive topographic and cartographic system in Slovenia. The authors have tried to point out the existence of these data and their structure, from which it will be possible to form one’s own picture about the usefulness of such data for various needs at the national level as well as for the needs of local communities.
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