Digital Terrain Model for Territory of Bulgaria
Marian Nikolov, M.Sc.
Research Associate
Military Topographic Service
BG 1000, Sofia, Bulgaria
Tel: + 359/ 2 /81 28 23 68
email: mts@acad.bg
Assoc. Prof. Dr. Raina Pavlova,
Technical University of Sofia
BG 1756, Sofia, Bulgaria
Tel:+359/ 2/ 636 34 53
email: rsp@vmei.acad.bg
Abstract
The process of primary collecting and acquiring of digital data and their organisation in a database is described in the paper. These data contain relief, hydrography . road networks and counter of the settlements got from topographic map in a scale 1:50000 .
A data model of a GIS dataset with the attributes is presented .
1. Introduction
The current development of the IT gives wide range of possibilities for designing of Information Systems containing various data of the environment . Together with the classics geodetic and cartography mapping in many areas of economy , government administration, defense and military there is a lack of terrain data related to various descriptive and statistical information. From the beginning of 80s a lot of works is done in this direction in our country. The government institutions responsible for the collecting and maintaining of geographical data are the Military Topographic Service (MTS) of the Ministry of Defense and Main Department of Cadastre and Geodesy of the Ministry of Regional Development and Public Works.
The most significant activities of collecting of digital terrain information for the whole country are the development of digital elevation model by the MTS and organising and maintaining of the digital data which diverse from the Land parceling reform carried out by the Ministry of Agriculture and Agrarian Reform. In the same time a lot of private companies and other organisations are working on creating of digital geographical and statistical databases concerning different goals and reflecting different parts of territory of Bulgaria.
In this paper the authors present a digital terrain model of the whole territory of Bulgaria developing by the MTS . The structure of the model is regard with the requirements of the basic GIS which will be developed in the future. In the model the data of relief, road network , hydrography and settlements in the scale 1:50000 are used.
2. Basic GIS
One of the main tasks of MTS is to support the army as well as other different organasations and establishments with a terrain information. For these purposes some products as topographic maps in scale 1:25000 - 1:100000, different kind of special maps and photographic documents , astronomic - geodetic data etc. are produced . It is obvious that there is a need of an integrated GIS which could support all these activities.
According to its aims and purposes a certain GIS could contain different data by their type, volume and accuracy. Such a GIS could be oriented to a specific application area. To satisfy the needs of activities carried out by the MTS a new basic GIS reflecting all the elements of a topographic map with their features is under development. In order to meet the big range of customers’ demands some additional elements and attributes will be selected and input in the dataset during the process of collecting of terrain data. These additional data will be implemented together with the basic GIS in an united integrated system. From the integrated system various applied GIS intended for deciding specific tasks could be generated .
The main product , the core , of the basic GIS is the digital terrain model. The model is created by the MTS while in the designing of the basic GIS different experts, specialists from MTS and other organizations and private companies will take part. The project of the digital terrain model is financed by the MTS but some attempts of finding out of an additional financial support are caring out.
3. Model
The aim of the model is the development of application software assuring the editing of attributes and geometric data for each layer, automation of the process of source data correction and map printing. Some possibility of data inquiring, analysis and 3D visualizations are envisaged. As a result of the model a derivative digital terrain model containing geographic data structured and topologically related in layers in vector and raster format is obtained. The created model will be used in future development of GIS.
The main sources for obtaining of digital geographic data are separated originals of topographic maps in scale 1:50000. The elevation data were collected by digitising of every contour and putting their heights as attributes. Only more important objects of the road network, hydrography and border of settlements are digitised. The digital data are organized in files by map sheets in scale 1:50000 in different formats of relief and road network, hydrography and border of settlements.
GIS ARC/INFO software is used for the development of the terrain model. An applied software is created for data processing. The source data are executed till organizing them in layers with attributes and topological structure. Relief data are organized in map sheets in scale 1:50000 regarding to the international tailing. On the base of source vector data a regular matrix with cells of size of 10 meters is generated. The rest features of the terrain - road network, hydrography and settlements for the whole country are stored in layers. In addition digital data for vegetation will be gained from a topographical map in scale 1:100000.
The features of a topographic map maintained in the digital terrain model are shown in table 1.
Feature of map |
Name of layer |
Type of layer |
Road network |
road |
line, route systems |
Rail network |
rail |
line, route systems |
Rivers - lines |
river |
line, route systems |
Rivers - polygons |
riverp |
Polygon |
Reservoirs, lakes |
lake |
Polygon |
Border of settlements |
town |
Polygon |
Contour data |
cont |
Line |
Regular matrix of relief |
grid |
Grid |
Vegetation |
veget |
Polygon |
Regular matrix of vegetation |
vegetg |
Grid |
Table 1
The digital model is maintained in layers of ARC/INFO format. For each layer a correct topological structure is maintained depending on its type. The attributes shown in table 2 are linked to the corresponding attribute tables.
Cover |
Attribute |
road |
type, type of surface, width, code |
rail |
type, number of railways |
river |
type, name |
riverp |
type, name |
lake |
type, name |
town |
type, name |
cont |
Elevation |
grid |
Elevation |
veget |
type, average height |
vegetg |
average height |
Table 2
4. Applied software
For generating of the digital terrain model and its maintaining an applied software is developed by the staff of MTS. The applied software is created in ARC/INFO environment with the following functions:
A general schema of applied software in ARC/INFO environment is shown on figure 1.
Figure 1
Currently the data are maintaining only in ARC/INFO format but a Vector Product Format for data exchange is foreseen in the future.
The created digital terrain model allows its use for different network analyses. For this purpose route systems of road network and hydrography are created.
The created digital terrain model will be used for design and development of base GIS for Bulgaria.
References