Remote sensing for resources development and environmental management: Remote sensing for resources development and environmental management

Damen, M. C. J.

Bibliographic data

Multivolume work

Persistent identifier:: 856342815

Title:: Remote sensing for resources development and environmental management

Sub title:: proceedings of the 7th international Symposium, Enschede, 25 - 29 August 1986

Year of publication:: 1986

Place of publication:: Rotterdam; Boston

Publisher of the original:: A. A. Balkema

Identifier (digital):: 856342815

Language:: English

Additional Notes:: Volume 1-3 erschienen von 1986-1988

Editor:: Damen, M. C. J.

Document type:: Multivolume work

Volume

Persistent identifier:: 856343064

Title:: Remote sensing for resources development and environmental management

Sub title:: proceedings of the 7th international Symposium, Enschede, 25 - 29 August 1986

Scope:: XV, 547 Seiten

Year of publication:: 1986

Place of publication:: Rotterdam; Boston

Publisher of the original:: A. A. Balkema

Identifier (digital):: 856343064

Illustration:: Illustrationen, Diagramme

Signature of the source:: ZS 312(26,7,1)

Language:: English

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Editor:: Damen, M. C. J.

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2016

Document type:: Volume

Collection:: Earth sciences

Chapter

Title:: 1 Visible and infrared data. Chairman: F. Quiel, Liaison: N J. Mulder

Document type:: Multivolume work

Structure type:: Chapter

Chapter

Title:: New approach to semi-automatically generate digital elevation data by using a vidicon camera. C. C. Lin, A. J. Chen & D. C. Chern

Document type:: Multivolume work

Structure type:: Chapter

Symposium on Remote Sensing for Resources Development and Environmental Management / Enschede / August 1986 51 New approach to semi-automatically generate digital elevation data by using a vidicon camera C.C.Lin, A.J.Chen & D.C.Chem Center for Space and Remote Sensing Research, National Central University, Chung-li, Taiwan ABSTRACT: A systematic procedure is proposed for semi-automatic digitization of topographic maps by using an interactive image processing system, including a vidicor camera. The required input is line-drawn contour map. A contour-line image is then generated by the vidicon camera. To produce a clean contour-line image with one pixel in width, standard preprocessing techiniques are adopted, such as image enhancement, noise-removal, line thinning, and editing etc. The resels and their corresponding boundaries are labeled automatically. Isolated peaks, flat ridges or troughes, are, then, added afterwards. A look-up table is manually generated, associating the elevation data with those points, lines or closed boundaries. The elevation value at a given pixel within a resel is weighted by the two smallest "effective distances" from this point to all of its neighbors, such as isolated points, lines or boundaries. The effective distance, defined here, represents a shortest distance between a point and a curve with the connecting path lying within a resel, i.e., the intersection with the contour lines are not permitted. A,fast computing algorithm is developed to calculate the effective distances of all the pixels within a resel. The construction of a digital elevation model is easily achieved. The main advantages of our approach are two-folds. Firstly, the variation of the elevation values within a resel is well behaved, regardless the complexity of a resel, even for elongated kindly shape, etc. Secondly, the ridges and troughes are automatically generated and clearly repersented. A simulated results will be presented to illustrate the processes and demonstrate its advantages. 1. Introduction: Topographic data are nowadays most commonly obtained through the technique of comparing optically photographed stereo pairs of imagery. Large amount of manpower is needed for applying this method. However, owing to its great importance, contour maps are prepared with various degrees of accuracy for most parts of the world with this or other less efficient methods. Satellite images, so far, are not suitable for extracting precise topographic information(Mckeown, 1984). Yet for many geological, hydrological, forestry or enviromental applications, it is necessary to have the digital elevation model (DEM) (Ragan 1975, 1978). The DEM, thus, also constitutes an indispensable layer for constructing geographic information system(GIS) (Ragan et al., 1976; Colwell, 1983; Faintich, 1984). Interpolation methods have been used to generate DEM (Tempfli, 1977; Grimson, 1981; Sincar et al,1984). One of the approaches is that, based on the given elevation values of some points the elevation values of other points in a region are interpolated (Rioley, 1981). Softwares using this approach are available commercially (SACM, 1981). Recently, raster scanning system, such as vidicon camera, becomes more widely available. With the aid of such system, we can use the contour line map, in raster format, as the basis of the interpolation. In a recent article, Sircar and Ragan (1985) described such a interpolation process, with a method of steepest decending and 4 reference lines. And it is adaptable to the small users who need to obtain a reasonable accurate DEM in a short period of time. This process, though efficient, cannot spread the elevation information uniformly in certain types of terrains, e.g., in an elongated kidney-shaped trough, the. elevation information in one end of the trough may not be conveyed to the other end. Nevertheless, such types of terrains are frequently encountered in a mountainous area where DEM is particularly useful. An algorithm that is capable of spreading the elevation information uniformly in any type of terrain is presented in this paper. The algorithm is also suitable for small user to generate DEM quickly. In section 2.-, prepossessing of the contour line image is discussed. In section 37 , effective distance within a resel is defined. In Sesction 4., a fast algorithm is devised for finding the interpolated elevation values. In section 5., an application example is presented. Finally, concluding discussions are offered in section 6V. 2. Digitized Contour Line Image and Preprocessing The image produced by a vidicon camera from a contour line map, e.g., the line-drawn map shown in Fig.l, usually has some defects. Hence some preprocessings are always necessary. The purpose of Fig. 1. The line-drawn map copied from topomap.

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