نشریه اطلاعات جغرافیایی (سپهر)
پیاپی 54 (تابستان 1384)

In order to describe the generalization process for classes of selective phenomena, we describe the sequence and probable order and determine which operators and generalization algorithms will be used. The generalization operator specifies the type of "generalization" conversion that must be applied, then the generalization algorithm is used to implement a particular conversion. In the presentation of the characteristics report a series of covering maps of Switzerland is used.

The Operational System of Linear Scan (OLS) of the Defense Meteorology Satellite Program (DMSP) has a unique ability in discovering visible and near-infrared (VNIR) portion of the electromagnetic spectrum at night. With visible band data of OLS, it is possible to find clouds that are illuminated by the moonlight, as well as light of cities, towns, industrial spots, gas burners and temporary events such as fires and clouds that have become bright by lightning. This paper describes the methods that have been developed to discover and determine the location of VNIR release sources; of course, it is carried out to detect fixed spatial propagation centers by cities, towns and industrial areas using DMSP-OLS overnight data and analysis of multi-time image series.

Today quality of human life is unstable, therefore it is necessary to assess the quality of human environment and identify the causes of instability. This requires identifying the variables affecting the environment, achieving a method for having and assessing criteria for supervision and control of the responses that society takes to repair instabilities. Environmental, economic, social and cultural indicators have emerged as a key tool for definition and follow-up of operations and strategies that lead to a sustainable development and analysis of the benefits and costs of development. According to these indicators such as literacy, income, poverty eradication, health, enjoyment of healthy water and air, leisure, women's participation in social, economic, cultural and environmental activities, etc., it is possible to assess the stability and instability of society, and in order to achieve sustainability, all indicators of sustainability should be considered simultaneously. In the course of development, it is undesirable that some people grow economically and the rest remain in poverty. In addition, it is necessary that the development be in a manner that it realize social and political solidarity, coordination in practice, participation of all sectors and individuals (including women) and increase of technological productivity while avoiding ecosystem degradation.

With the increase in industrial activities and the following climate responses, the development of marine oil fields, wars and the change of regional policies, especially the Iraqi invasion of Kuwait and the American invasion of Iraq, significant amounts of chemical, hydrocarbon and radioactive substances have entered the seas and the hydrological cycle and have created irreparable damage to the life cycle. In this paper, we carry out a brief overview of each of the cases.
 

Since it is possible to achieve precision of two centimeters (or better) for orthometric altitudes (perpendicular to geoid) derived from GPS, this paper is intended to provide a brief and practical guide to the use of GPS devices, methods of reference determination, data collection and geoid models that provide surveyors with high-precision orthometric altitudes. Although this paper is basically written for American surveyors, all other surveyors can benefit from the experiences collected in this paper as well. Achieving two-centimeter precision for GPS-based orthometric altitudes can be achieved using iterative, radial and fast static GPS techniques along with a high resolution geoid model. These methods can be implemented in an area of ​​less than 30 km2, and since field GPS methods and observation time periods are not directly proportional to the length of the base line, these methods can not be immediately applied to large-scale projects (i.e., Lands with areas more than 30 km2). The author of this paper intends to present a brief and practical guide and is not to provide a substitute for the GPS manual, but to create an incentive for surveyors to study the device's manual with great attention.

Precipitation is a climatic element that changes year by year, and in fact precipitation is a random variable over time. If long-term precipitation data are available, the probability of occurrence of precipitation can be determined by statistical methods. In this study, the city of Semnan has been selected in order to determine the probability of annual, seasonal and monthly precipitation. Precipitation data in this city have been analyzed using computer software and statistical methods. Wet and dry periods, seasonal and monthly variations in precipitation and the probability of occurrence of seasonal and monthly precipitation have been determined.

Since Quaternary organizations form the basis of human society's life, the Quaternary study is the study of the enormous and potential natural reserves of each country, which should be the study-basis of sustainable development. High-resolution satellite digital images with different wavelengths, along with utilization of GIS systems and special data processing software, have provided commentators with the possibility to study various issues related to natural resources with very high accuracy and speed. Accordingly, in this paper, using ETM Landsat satellite images, a method for the preparation of Quaternary alluvial maps has been proposed. In order to carry out this research, after collecting required data and ETM Landsat satellite images, these data were processed and a Quaternary map was prepared in the GIS program environment. By summing up the results, we can say that from a combination of 6 bands (bands 1, 2, 3, 4, 5 and 7) out of the seven information bands of ETM in the range of visible to thermal near-infrared wavelengths, different color composites for the purpose of separation of lithological units were fabricated, the best of which being a combination of three bands of 5, 3 and 1. In this image, various lithological units are well separated, and by carrying out the necessary examinations, its accuracy was estimated to be about 90%, which indicates a very satisfactory coefficient of reliability. Using the results of these studies, we can identify and exploit the potentials of this system according to their visual characteristics.

On March 13, 1781, an amateur musician and astronomer, William Herschel, discovered the planet of Uranus at night. First, he didn’t understand what he had discovered and confused it with a comet. Herschel accidentally succeeded in discovering a dim and unusual star when he was exploring the sky with his 15 cm reflecting telescope. When he raised the magnification degree of his telescope, this unusual object appeared larger. When Herschel could believe observing this object in the sky, the stars that were in the vicinity of this object were still undefined points of light in the sky. He was able to gain more clues and information during other nights when this planet slowly passed through the stars. The luminosity of this body, which was part of the solar system, was less than a star, and most of its features indicated that it was a comet. Herschel presented his discovery to the Royal Institution of Great Britain under the title "Describing a Comet".

The phenomenon of flood in its current state in our country is caused more by the effects of interrupting the balance of natural ecosystems in the country than by the occurrence of low-probability precipitation. In the form that we can observe today, the occurrence of ordinary rainfall in most watersheds of the country causes flood. According to available statistics, in parts of the world, especially in Asia and the Pacific, flood damage accounts for the highest proportion of damages caused by natural disasters. Despite the fact that no comparative statistics on flood and earthquake damage in our country have been published so far, Iran is nevertheless considered a flood-prone country, having arid and semi-arid climatic conditions. The province of Hamedan is among the flood-prone areas of Iran due to natural and human factors contributing to the occurrence of flood. The occurrence of historic floods such as floods in 1987 and 1992 in this province illustrates this fact. Flood factors fall into two categories: natural factors including climatic conditions (repeated rainfall, snow melting, high temperatures ...), land features (slope, soil texture, etc.) and poor vegetation, and human factors. In Hamadan province, the above factors have in mutual cooperation caused conditions favorable to flood which are mentioned in this study.

The tectonic activities that have led to the creation of closed lakes in Iran, the important fact that Iran is located at subtropical high pressure region, the country’s distance from the sea and its being enclosed by heights are the reasons that caused the abundance of deserts in Iran. The question here is that how can we use this geographical position in the development of tourism industry in Iran? Simultaneous planning for utilization of original geographical environment, Iran's deserts and its closed lakes, camel trips, visiting historic regions and tribes settled in these areas (such as the nomads), buying souvenirs and ... can all be remarkable in this regard.

Since the foundation of the Naghsh-e Jahan Square, the significance of this square has been increasing due to the existence of historical monuments and traditional markets around it, and there is rarely anyone who has no desire to see this square or not have enjoyed its visit already. It would then be nice and desirable to make an optimal economic utilization of this great potential of tourist attraction, so that in addition to the prosperity of the market for handicrafts and creating employments for young people in this market and so relieving them from unemployment sufferings, we can keep the art and reputation of the art of the artisans of Isfahan alive.
 

Geomorphology is one of the branches of geosciences which is related to forms of terrain (topographic reliefs) of the Earth's Crust. The contact area studied by geomorphology is affected on the one hand by internal forces such as tectonic forces and volcano, and on the other by exogenous forces, i.e. erosion, which originate in the hydrosphere of the atmosphere. Geomorphology forms one of the largest natural units which has a very close relationship with other natural units. Identifying the principles of these relationships in order to understand them and consider and utilize them in developmental plans is one of the goals of geomorphology. As the term “geomorphology” suggests, the study of landforms and their changes and changing factors are among the topics and objectives of this science. In the morphogenetic domain of Sahand, important changes in topographic shapes, which are among the prominent features of this region, can be caused either by sequential function of internal and external factors or simultaneous operation of these forces, hence in this study attention has been paid to each of the internal and external factors. Clear effects of these changes can now be observed in the present appearance of Sahand. The study of natural environments and environments occupied by human beings is carried out by many sciences in order to exploit them more and more correctly. In this study, a part of this objective has been fulfilled by relying on Sahand geomorphologic study to identify the factors affecting evolution and morphogenesis. The content of this research does not at all include all the issues of the Sahand Mountain Range, and it can not be said that this study ends here, but there are many discussions concerning the high mountainous regions and the low basin areas that remain and require further studies. Today, due to the increasing number of population, in order to use natural areas ever more, as well as create new living environments and recreational places for humans, mountainous regions (in spite of the many difficulties) should be paid attention so that they become able to respond to some of the economic and residential needs.