Complex method for developing the digital geomorphologic map of Romania at 1:200.000 scale.

Badea, Alexandru ; Moise, Cristian ; Dana, Iulia Florentina 等

1. INTRODUCTION

The first complete geomorphologic maps were achieved at the beginning of the 20th century and they included particular representations of the studied areas. In 1965, at the congress International Geographical Union (IGU) from Rio de Janeiro, there were presented two new ideas in approaching the geomorphologic maps: the introduction of certain specific elaboration methods in geomorphology and the adoption of a standard plotting system.

When Remote Sensing and Geographical information Systems developed, geomorphologic plotting was decisively influenced, as the interpretation and representation of the relief elements was eased by comparing the field data with the satellite ones or by the development of diverse algorithms of the map algebra type or of automatic calculus and integration of the morphometry, geodeclivity, insolation, or slopes' exposure data.

In spite of the fact that geomorphologic maps continued to evolve during the last century, there was not reached a universally accepted mapping system and there still are differences with regard to the form, content, and cartographic symbols (legend). Presently, a very powerful organism involved in unifying the geomorphologic approaches is the International Association of the Geomorphologists (IAG/AIG), where, under the coordination of EC, activates a work group that is working at a project the main objectives of which are the following:

* development and deepening of the theoretical base knowledge in the field of applied geomorphologic mapping

* development of standards, mapping procedures, and types of legend for different applications and scales

* dissemination of the importance and efficiency of using geomorphologic mapping as a base instrument for those who study the environmental problems the purpose of which is to establish links among different scientific and professional communities

In Romania, a major achievement of geomorphologic mapping was the elaboration of the general geomorphologic map of Romania at a mean scale of 1:200,000 by the Geography Institute of the Romanian Academy (Figure 1).

[FIGURE 1 OMITTED]

The drawing of the map at a scale of 1:200,000 started in 1977 and ended in 1990. The legend was elaborated according to the recommendations and the principles adopted by the Research and geomorphologic mapping commission of U.I.G. The unique and universally valid legend cannot be applied at all the scales, which determined the replacement of generalized aspects, used in small-scale representations, with more and more detailed features of the forms, specific to large-scale representations. This is why legends were differentiated on categories of scales. Thus, the attention focused on establishing the principles for the elaboration of legends (Posea, Popescu and Badea, Niculescu--1972) and for their application at different scales. The considerations presented in this paper are based on the above-mentioned general geomorphologic map of Romania at a scale of 1:200.000.

2. METHODOLOGY

The elaboration of a general geomorphologic map supposes the territory's investigation and knowledge display a uniform and detailed character in agreement with the map scale; moreover, it is necessary to make a geomorphologic analysis of the map, so that the fundamental morphometric elements (relief intensity and mean slopes) could be emphasized and adequately rendered. Relief intensity is a defining element in determining the classes of the relief forms, the main morphologic types--plains, hills, plateaus, and mountains, which represent, in fact, the association (assembly) of certain forms in their specific stages of evolution (Badea et al., 1983). Consequently, each trapeze has to be accompanied by a map rendering the classes of the relief forms or the relief units generically defined and hierarchically displayed by classes (as relief intensity and altitude), over which the lithological structure can be overlapped (Nastase, 1995).

The drawing of the general geomorphologic map was based on a set of original principles:

* the groups or types of characteristic elements have to be rendered by symbols, hachure, or colors, according to the importance of the phenomenon.

* the legend has to correspond to a certain scale or, more precisely, to a certain group of scales: small (1:1,500,000 up to 1:1,000,000 or even 1:500,000), mean (1:400,000 up to 1:100,000) and large (more than 1:100,000 up to 1:20,000) and to the features of the Romanian territory, which underlines the idea that the legend must not be universal.

* the possibility of including certain elements resulted from the elaboration of some special geomorphologic maps in the legend of the general geomorphologic map. The legend has to display an open character.

The elaboration of the legend respected the recommendations made by the IGU and the suggestions given for the legend of the Europe geomorphologic map at a scale of 1: 2.500.000 (1968,1971) and of the geomorphologic map at a mean scale (1973), obviously, by adapting it in order to better render the relief forms of Romania.

The legend of the general geomorphologic map (scale 1:200.000) contains five parts:

* the map of classes of landform

* the structural-lithological types and the cover deposits

* simple landforms and elements represented by symbols

* the genetic types of landforms (the most important section of the legend)

* declivity

This involves the classification of the map elements, and their separation to different types of vectors: polygon, line or point. Once these are set, they are integrated into a digital library of map symbols containing all necessary elements for the geomorphologic map.

The validation of the present geomorphologic maps is to be achieved by their correlation with the digital elevation models (DEM) at different resolutions and with high and very high-resolution satellite images.

From the geomorphologic point of view, a complete description of any relief forms can be achieved by using three elements: altitude, slope, and curvature (Posea et al., 1976). The slope is the most important element for describing the terrain surface. The determination of the slopes and of their exposure can be achieved by analyzing a digital terrain model.

There are used many types of digital terrain models, obtained from different data sources (topographical maps, satellite images undertaken by active and passive sensors, other data sources) (Figure 2).

For certain test zones, a digital terrain model will be generated by digitizing the contour lines from the topographical map at the scale of 1:25.000. The precision (accuracy) the relief forms are rendered within a topographical map is mainly determined by the density (equidistance) of the contour lines. The large--and mean-scale maps render, at high fidelity, the field elements, while the general topographical maps display an increased generalization level (Posea & Cioaca, 2003). Generally, the precision in altitude of a certain point determined by the interpolation of the contour lines is of 1/2-1/3 of the equidistance. In order to obtain certain results with a superior altimetric precision, a digital elevation model will be also generated on the basis of the topographical map at the scale of 1:5.000.

[FIGURE 2 OMITTED]

The processing of the satellite images overtaken by SPOT 5 HRS allowed obtaining a highly precision digital terrain model. This model contains up-dated information referring to the relief elements. As supplementary data, other digital terrain models are used: SRTM (generated through interferometry techniques) and DTED2 (informational content equivalent to the model generated by the digitization of the contour lines 1:50.000).

The precision of the digital terrain models are evaluated by means of statistical methods that include GPS measurements made in the field in the control points.

Starting from these numerical models, is to be achieved a comparative study, the purpose of which is the identification of the most adequate model for the up-dating and editing of the geomorphologic map at a scale of 1:200.000.

An extremely important scientific activity is represented by the development and testing of the correlated algorithms for validating the map symbols' position, dimension, orientation and shape.

3. CONCLUSIONS

The approaches of this project follow the line of implementing the European directives (Nature 2000) and the application and development of the INSPIRE (Infrastructure for Spatial Information in Europe) and GMES (Global Monitoring for Environment and Security) actions related to the environment protection and rehabilitation through the development and utilization of GIS/Remote Sensing techniques.

The output will be represented by the elaboration of the first geomorphological digital map of Romania at a scale of 1:200,000 and the elaboration of the first digital map symbols library specific to the Romanian territory.

The complexity of the project achievement solutions is represented by the study and testing of the methods of correlation between the different digital terrain models and the digital geomorphological layer, materialized through the development of software algorithms for the interactive validation of the map symbols characteristics.

We plan to use the results of this project in facilitating the drawing of the risk maps, of environment impact studies and optimizing the determination of the geomorphologic risk factors, all these being essential elements for most of the national, regional, and local economic targets.

4. REFERENCES

Badea, L.; Gastescu, P. & Velcea, V. (1983): Geografia fizica (Physical geography), Editura Academiei Republicii Socialiste Romania, Bucharest

Nastase, A. (1995): Cartografie (Cartography), Editura Fundatiei "Romania de maine", Bucharest

Posea, Gr. & Cioaca, A. (2003): Cartografierea geomorfologica (Geomorphologic mapping). Editura Fundatiei "Romania de maine", Bucharest

Posea, Gr.; Grigore, M.; Popescu, N. & Ielenicz, M. (1976): Geomorfologie (Geomorphology), Editura Didactica si Pedagogica, Bucuresti

***Atlas R.S.R. (1979), Editura Academiei R.S.R., Bucharest