Use of digital terrain modeles for the infrastructure development in sri lanka.
However, since large area coverage is achieved relatively at a low cost, existing topographic maps provide a compromise method of obtaining DTMs for use at medium or small scales.
Table 1 presents the three main methods which can be used to acquire the elevation data and applications of terrain models created at different scales.
Table 1: Sources of DTM data and applications
Construction Of Digital Terrain Models
After capturing of raw data sets, to construct a comprehensive DTM, it is necessary to establish the topological relations between the elements, as well as an interpolation model to approximate the surface behaviour. In order to do that a very large number of programme packages have been devised and written for terrain modelling and it's applications.
The general classification of terrain modelling software packages in surveying and civil engineering is illustrated in figure 3.
Figure 3 Classification of terrain modelling software packages in surveying and civil engineering.
Applications
Terrain modelling is applied as a solution to a wide range of problems in the field of surveying and mapping, geology, civil and military engineering. Being Sri Lank is a developing country, much more emphasis has to be made to identify the low cost methods in infrastructure development in the country.
Terrain models which can be created by using photogrammetry and existing maps are less expensive Hence, those techniques are ideal tools to solve problems in infrastructure development.
Feasibility Studies
Feasibility study is one of the main prerequisites of any major development project. Failure of feasibility study may be the failure in the entire project giving economical & environmental hazard to the country. Traditionally a feasibility study is done by manual data capturing techniques or by simply utilizing the skill and experience of the qualified experts. The method is highly time consuming and expensive.
Having generated a ground model of the proposed area, feasibility studies and environmental impact analysis can be performed automatically once the position of the proposed site is defined. Figure 4 illustrates the use of the technique to simulate the effect of a proposed highway on an existing ground model.
Figure 4 Simulated highway model created using the MTM Terrain modelling package
Communications Planning
In recent years use of telecommunication, radio and television, cellular and mobile telephones have increased in Sri Lanka.
The use of Terrain model data, in conjunction with computer analysis is widely use in many countries in this field. The applications are involved in the planning of communications network, rapid optimization of radio links, siting of transmitters, identification of complementary areas of coverage and prediction of areas subject to co-channel interface.
As lower accuracy DTMs could be generated with the help of photogrammetric and cartographic data capturing methods are quite suitable for the above, the method can be used in Sri Lanka to enhance the communication developments.
