نشریه اطلاعات جغرافیایی (سپهر)
پیاپی 51 (پاییز 1383)

Geographic information can be digitized in vector format and processed and transformed by satellite data (visual information) in a raster environment. Such systems are beneficial, but it should be noted that multiple transformations of vector and raster data will be carried out losing accuracy and at the expense of data degradation. A combination enables the processing of two vector and raster structures, hierarchical representation, and object-oriented search for remote sensing data to a fairly full extent. Satellite image analysis has the ability to combine and integrate one or more remote sensing models. Models are divided into empirical as against algebraic models, and invertible versus non-invertible models. Empirical models have reliance on linkage, sensor measurements and surface properties, while algebraic models rely on the heat and radiation transfer hypothesis. Models with inverse capability are those in which unknown properties of the landscape can be deduced from the measurements of remote sensing.

The road network and access routes are among the most important elements of military geography. Classification of road network, type of access and appropriate transportation conditions for transfer of human forces and freight on the one hand, and reliable access to road lines and passageways of bridges, tunnels and road structures on the other, are of great importance. The status of roads, railways, ports, airports and inland waterways which facilitate military operations and allow for support of forces, have a special place in military geography.

New cities are newly-built settlements that lack the previous initial core, built on a pre-designed plan and structure, with thousands of years of history in the world. Indeed, it can be argued that the discussion of new cities is as old as urban history, but the idea of creating new cities in its classical and extensive form should be sought in the early twentieth century. The Theory of New Cities is inspired by various theories, and Ebenezer Howard has been recognized as its main theorist. The industrial revolution and its consequences led to the expansion of urbanization and acceleration of urbanization, especially in mother cities, which have faced serious problems through industrial developments and expansion of capitalism in large cities. In developing countries, with increasing population growth, especially urban population, numerous problems have appeared. Disproportionate distribution of population across the countries and mass concentration of population in large cities has led to problems such as housing shortage, marginal settlement, high population density, traffic congestion, air pollution, destruction of agricultural lands around large cities, etc., which call for special measures. One of the measures was to create new cities to reduce major problems and organize the space in those areas. In fact, the goals and strategies of the new cities are often based on demographic decentralization. The urbanization process in our country has also been influenced by the developments and dominance of capitalism and has been steadily increasing over the past decades. The urban area of ​​Isfahan is not isolated from the situation of the urbanization system of the country and has high urbanization coefficients which has led to numerous consequences and problems in the region. In order to reduce these problems, absorption of population overflows of this city and settling the employees of the industrial sector in the region have been reviewed and creation of new cities has been confirmed. Shahr Jadid Baharestan (the New City of Baharestan) is considered as the main basis for this paper, which has been examined and evaluated through different frameworks.

Climate change in Iran and the world is considered by most scientists to be due to the emergence of “greenhouse” state that will have adverse effects on the Planet from different viewpoints. Due to human interference in climate change, undeniable climate change has been asserted in various world reports and the latest statements by the International Community, but scientific doubts also exist on reasoning behind climate change reported by “CHANGEINTERGOVERNMENTALPANELONCLIMATE”. As BRYSON (1977) states, surge from one pattern to another might change the climate of some of the mid-range-latitude areas drastically, and it is very likely to create a “drought-or-flood” pattern. The increase in temperature in some of Iran's meteorological stations indicates a tendency towards arid climate, and probably the period of climate change has begun in the country of Iran. The country, according to the research, has a pattern of a number of years of droughts alternated by a number of rainy years. Environmental problems such as global warming, frequent occurrence of droughts, expansion of deserts and the increasing trend of desertification, increasing number of forbidden areas for the extraction of water and occurrence of destructive floods have caused ecological instability in the country and have increased the vulnerability of the country's natural resources.

The deposits existing in the ice is formed by materials part of which is deposited by water (in terms of particle size) and irregularly structured in melting ice. Sedimentation can occur on, opposite to, or under the destination area of ​​the ice river, and is possible to be irregular and individual. Ice is likely to melt from the contact with sediment collected beneath it, or from the position beside it, which leads to falling, subsidence or slipping. Principles of formation of land by this process are the rows of sand and small hills of rock and soil belonging to the Ice Age.

Like other natural phenomena of the universe, the inclination angle of the axis of the Earth is significantly variable. These changes can be divided into two groups. First, regular cyclic changes of the inclination angle of the Earth, which is part of the Milankovitch changes, and whose magnitude of positive and negative values in every 41,000 years ​​are plus and minus 3.5. The second, long-term geological changes of the Earth's inclination angle, which seems to be one-sided and gradually decreasing since the beginning of the Phanerozoic Era (450 million years ago). Factors such as friction caused by tidal waves and separation of the Earth’s Flesh and Crust have contributed to this phenomenon. Long-term changes in the inclination angle of the Earth and its decrease have caused the formation of seasons as well as climatic division of geographic latitudes.

For geographic applications such as surface flow models, 3D visualization, simulation and analysis of visibility potential gaining information about land features (land’s lay) is a necessity. Basically, the Digital Terrain Model (DTM) includes sampling few points of the real world. Interpolation is still a difficult task in order to reconstruct a continuous surface of sample points. In this paper, the author attempts to discuss current issues of DTM production and interpolation technology including continuous advancement in information technology and increasing need of users to digital land models.

North American meteorological advisors implemented the summer plan of cloud insemination in the countries of Guatemala and Honduras. The two countries, as their neighbors in Central America, provide the bulk of their electrical energy from hydroelectric power facilities. The Chixoy dams in Guatemala and El Cajon in Honduras provide more than 50 percent of the electric power consumed in these two countries. Usually the Chixoy dams are filled with water in the summer, but this dam was not filled in 1991 due to a strong case of the El Nino, the fact which led to disruptions in production of hydroelectric power. For this reason, the fertility plan was implemented in the months of October and November, which correspond to the end of rainy season. Opportunities for insemination were limited. A more comprehensive plan was conducted in late May until July and late September until late October, 1992. The goal of this plan was to increase rainfall on the Chixoy River Basin. The preliminary assessment indicated that the possible fertilizing effects during June 1992 was an average of 17% increase in rainfall in several precipitation control stations facing the wind. According to preliminary calculations, the runoff cost potential of this fertility plan was about a few American dollars per Acer Foot. A similar plan was implemented from late August until late November 1993 on the El Cajon River Basin, Honduras. The preliminary analysis of possible effects of this fertility plan is currently in progress.

The use of marine data and information and depth measurement are among the technical requirements of major and minor decision making by the government and private sectors of the country. To use this information, which is increasing day by day in great quantities, and to use different information layers, we need a coherent database, knowledge of data and proper and powerful functions. In this paper, it has been tried to identify and categorize hydrographic data according to the stages of construction of a GIS. Next, the required models for representation of dynamic data have been examined and a general view of the manner of using HIS has been presented.

This paper is about sustainable development and its constituent elements in urban planning, and in order to introduce this issue, which has an important place in urban studies and literature. From the review of environmental studies on city and urbanization issues, it has been deduced that citizens should be the main focus of all urban plans, and inattention or neglect of the environment leads to deep crises in human being’s living environment, including urban environment. Establishing areas for participatory planning development (citizen participation in urban plans), ensuring the participation of all groups with interest in the city’s affairs, coordination among minor and major plans, promoting and expanding sustainable urban development methods and utilizing auxiliary tools for urban management form the main theme of sustainable urban development.

Astronomers constantly look for a way to improve techniques and methods of observing the universe. One of the common ways is to use larger and higher-quality telescopes to take pictures from the sky with greater clarity and detail. However, their antennas are physically limited in size and shape, since they must be extended extremely accurately, and for optical telescopes, their optical component must be highly inflexible and accurately shaped. On the whole, astronomers have infrequently criticized the accuracy and advantage of these telescopes. At the moment, the world's largest telescopes are radio antennas that provide the most detailed images of the universe by combining signals from radio telescopes. This method is called the Very Long Baseline Interferometry (VLBI), and can provide images of space objects that are of a thousand times greater in resolution than those of the Hubble Space Telescope.

Today, thousands of satellites revolve around the Earth with diverse aims, and each of these satellites is at a certain distance from the Earth depending on the purpose it pursues. Satellite plays an important role in scientific research and communication, and it might be said that these satellites have made the Global Village a reality, and thus play a crucial role in present-day civilization. Contrary to common ideas about ​​satellites, they are not immune from effects of environmental factors in their surroundings, and are indeed influenced by factors such as the Sun and solar activities and other atmospheric influences, including the coronal material of the sun, solar flares and .... In this paper, we intend to briefly describe some of the factors producing disorder in the work of satellites or affecting their life-span. Among the strengths of the paper is the up-to-date quality of most of content, including the fact that most of these materials have been discovered in recent decades, and we have obtained them from the latest Internet websites and articles.

According to existing statistics, the tourism industry, as the second source of foreign exchange earnings in 49 developing countries, has a major role in the economic development of these countries. Today the tourism industry is referred to as a powerful arm for increasing income and reducing poverty in developing countries. The importance of tourism industry is so significant that for the first time in the recent United Nations Charter, declared at a session held with participation of representatives from developing and developed countries, the chairmen of the United Nations, the World Trade Organization and the Secretary-General of UNCTAD, developed countries have been called upon to help the countries of the Third World participate in the growth and promotion of this industry in the world, and to take part in poverty alleviation in these countries through supplying necessary facilities and investments. Given that Iran is one of the top ten countries in terms of tourist attractions, and this industry can replace the oil-based one-product economy of Iran, solutions to the challenges of this industry in the country and its improvement should be in the agenda of related organizations. It is hoped that the issues discussed in this paper and the suggestions and conclusions obtained act as a strategy for development of tourism in the country.

In geographic studies, soil is not the focus of attention only as a natural resource, but more of a crucial asset which is exposed to a fatal threat called erosion, and thus needs to be examined, protected and maintained. From the point of view of geomorphology, the concept of erosion is on the one hand connected with the processes affecting the face of the earth and, and on the other, with factors that act against soil conservation. It is clear that the level and type of erosion of soil varies from place to place, and awareness of these quantities can be greatly useful in planning. The concept of erosion is a very broad and deep topic in geomorphology that can be considered from different perspectives. The geographic concept of erosion is not the same as its concept as considered in geology, physics or soil science. The term erosion is derived from the verb “to erode”, and is referred to as the set of processes in which the external surface of the earth's crust loses its stability and is displaced. This concept involves the processes of degradation, dissolution, carriage and sedimentation. According to studies conducted in Iran, an average of 1,500 tons of soil is washed out by water erosion per year. This means that every year, one millimeter of soil thickness in the country is lost (Karami, 1993, thesis) Considering the position and characteristics of Najaf Abad Plain watershed system, it seems that the energy generated by collision of rain drops to the surface of the earth and the resulting runoff is the most important erosive force in the watershed system, which, in interaction with erodible factors, determines the rate of soil erosion. Therefore, in this paper, in order to assess the erosion dangers and estimate its quantity and level, the application of the SLEMSA model has been emphasized, because in this model, utilization of curvature correlations and consideration of the interactions of the factors involved in erosion are given the priority.

Since drought is a very complicated phenomenon, it is very difficult to understand all aspects of this phenomenon and all the problems arising from it. On this basis, there is still no comprehensive definition or a single type of examination of drought unanimously accepted by experts in the field. In this study, drought trend of Yazd province was examined in terms of frequency of dry and rainy months using standard deviation index (compared to the monthly average rainfall) during a statistical period of 30 years in 26 stations, and it was shown that in the Abarkuh, , Dehshir, Khuyrak, Saghand and Mazra’e-no stations 54% of the time examined was without rain, and in the Abarkuh, , Dehshir, Khuyrak, Saghand and Yazd stations in almost 77% of the statistical period the precipitation was less than the normal monthly precipitation.