Ignacio Cañas Guerrero

3-D expression of relief in Landsat Thematic Mapper and SPOT P images

Perceptual problems of viewing topography on geoimages are caused by illumination from the southeast during data collection. This problem affects the majority of satellite images. The aim of this work is to obtain a stereoscopic effect of shaded relief in such images. Techniques available in commercial digital processing programs are used in the absence of a digital elevation model. The images used are taken by the Landsat TM and SPOT P satellites; the software used was the EASI-PACE and ACE programs (Canadian PCI Geomatics Group). The pseudoscopic effect is solved by using the first principal component obtained in a principle components analysis of the three channels, resulting from the weighted merging of the Landsat and SPOT data. The map obtained provides the observer a view with shaded relief.

Detection of buildings through automatic extraction of shadows in Ikonos imagery

The extraction of man-made objects from remotely sensed imagery is a common application in remote sensing. Building detection is useful in territorial planning, mapping and Geographic Information Systems. Nevertheless these features are difficult to recognise in satellite data because of their variations in structure and size and especially because of the spatial resolution of the imagery. IRS panchromatic data, with 5,8 meters pixel size, was the higher spatial resolution sensor in civil applications until the Ikonos imageries distribution. Several approaches have been proposed for building detection in aerial images. Buildings cast a shadow in some direction and that is why many authors have employed shadows to detect constructions. Other authors use shadows to verify them, once they have been detected by some other techniques. This work focus on shadows detection probabilistic methods: it is found that digital supervised classification of the first principal component obtained from the application of a principal component analysis on the four channels of Ikonos allows identifying shadows and distinguishing them from other covers in the image. It is a fast and effective method and it can be implemented through tools available in commercial remote sensing software. This shadow detection system will provide cost-effectiveness in the inventorying of buildings, especially in areas of dispersed settlement, given that it significantly reduces fieldwork, and even can function as a support and test of the methods of automatic extraction of buildings from satellite images developed up to now.The extraction of man-made objects from remotely sensed imagery is a common application in remote sensing. Building detection is useful in territorial planning, mapping and Geographic Information Systems. Nevertheless these features are difficult to recognise in satellite data because of their variations in structure and size and especially because of the spatial resolution of the imagery. IRS panchromatic data, with 5,8 meters pixel size, was the higher spatial resolution sensor in civil applications until the Ikonos imageries distribution. Several approaches have been proposed for building detection in aerial images. Buildings cast a shadow in some direction and that is why many authors have employed shadows to detect constructions. Other authors use shadows to verify them, once they have been detected by some other techniques. This work focus on shadows detection probabilistic methods: it is found that digital supervised classification of the first principal component obtained from the application of a principal component analysis on the four channels of Ikonos allows identifying shadows and distinguishing them from other covers in the image. It is a fast and effective method and it can be implemented through tools available in commercial remote sensing software. This shadow detection system will provide cost –effectiveness in the inventorying of buildings, especially in areas of dispersed settlement, given that it significantly reduces fieldwork., and even can function as a support and test of the methods of automatic extraction of buildings from satellite images developed up to now.

Approach to Greenways and Natural Paths in Spain

Greenways and natural paths are a way of providing enjoyment, promoting the cultural and landscape knowledge of an area, providing exercise, and encouraging respect for the environment. The aim of this paper is to analyze some physical characteristics of greenways and natural paths in Spain. The papers introduction clarifies some concepts and provides historic references. To achieve the objective of this pilot study, successive meetings with representatives of the Spanish Ministry of the Environment and the Spanish Railway Foundation were held to learn about previous projects. After some of these projects were reviewed, various characteristics of the paths, including users of the paths, typology of the platform, and reforestation, were analyzed. Results of the analysis are presented in tables, which show that greenways tend to be more uniform than natural paths, which have more variable features. After the analysis, the most common characteristics of Spanish natural paths and greenways are presented.