نشریه اطلاعات جغرافیایی (سپهر)
پیاپی 60 (زمستان 1385)

Many of sciences undergo constant transformation through connection with modern technology and make progress, and are provided with equipment of great value through ease in the methods and fast fulfilment of necessities. The science of cartography, under the influence of modern technology (positioning and imagery satellites, databases and digital systems, etc.), has undergone a radical and extensive development. The reliance on "modeling" is a world of constructive relationships between geomatic technologies and sciences in applications. Creating spatial and geographical database presents a smart product for different sciences that provides the ability to determine, identify, organize, combine, display and manage information. In geographic information system environment, the arrangement, combination and visualization of different ways of implementation of a geographic position can be carried out using the power of automatic computer sampling in a proper way. The visualization of data in a geographic system environment places the user in logical decision-making conditions. Because in this environment, it is possible to store separate pieces of geographic space in the form of point, line, surface, and text records that make up the final composition of all elements and geographic phenomena, and, if needed, to display them in one place in the form of a single image, and most importantly, if necessary, to connect their contents to each other. Components of images taken from the real world are carefully recorded in the memory of computer with a special character encoding. This type of data helps users place images and objects together in a regular, meaningful and organized way in a geographic space. Creating spatial database is a platform for creation of intelligent information that helps users in understanding, analysis, and proper decision-making. On the basis of a spatial database, geographic data can be increased and geographic information systems formed, and the more various qualitative and quantitative characteristics associated with spatial features, the higher the level of intelligence of database. Several organizations are seeking to publish their spatial and geographical information using the Web GIS so that different users, such as decision makers and planners, can access this information regardless of time and place constraints. Web GIS is a spatial and geographic information system distributed in a computer network used to integrate and disseminate graphic information on the WWW and on the Internet.

The Persian Gulf has a prominent geographic position. Natural conditions such as little depth, water salinity and high evaporation on the one hand, and limited communication with open lands of the world on the other, have created a special ecosystem within the Persian Gulf and its coasts. The Persian Gulf has long been regarded as one of the most important strategic regions of the world. The Persian Gulf region is a geopolitical unit located in the wider geostrategic basins of the Indian Ocean. The geographic region of the Persian Gulf acts as one of the most active economic centers in the world. It’s major exports are oil and gas and it’s imports mainly consist of industrial and food products. Natural potential and vast oil and gas resources have contributed to the establishment of a single-product economic system in coastal countries.

The Orient is the birthplace of civilization, and Sistan is one of the centers of culture and civilization in Southwest Asia. Sistan is also the birthplace of the national, cultural and social epics of ancient Iranian history. Sistan Plain, located in the eastern part of Iran, is the center of one of the ancient civilizations due to its special geographical position in the mouth of the Hirmand River and its branches, and the exploitation of its water resources and fertile alluvium in the light of agricultural activities and cultural functions. According to archaeologists' findings, in a few millennia B.C., one of the oldest urbanization and civilization models was formed in the burnt city of Sistan, more ancient than the Sumerian civilization. The Sistan province, thanks to its geographic location, has since the dawn of history enjoyed such an economic enrichment that has won for it the title of "Asia's Granary." In this paper, which is prepared by methods of secondary and analytical research, the researcher has tried to determine the antiquity, status, the real face of historical geography, economic, cultural and social role of Sistan among the civilizations of Southeast Asia through collecting and analyzing historical and geographical documents. مراجع

New cities have a history of several thousand years as newly built settlements without initial nuclei, which are based on previously thought plan and structure (Narimani, 1998, p. 12). In Iran, due to changes caused by influence of capitalism, urban network and system have gone out of equilibrium, and phenomena such as concentration of regional metropolises, population accumulation, massive migration and accelerated urbanization have come into existence that have in turn led to many problems. In this regard, the policy of constructing new cities was raised in late 1985 as a practical and scientific solution for reduction of these problems and as a new experience and fundamental movement in the country's urban system.

One of the biggest problems concerning natural resources is the issue of soil erosion. With loss of soil, the most important source of human production is eliminated, a disaster which is impossible to compensate for. In order to accurately identify the factors of soil degradation, exact basic information is needed. Today the existence of instrumentation systems and different models have enabled human being to store and, if necessary, recover basic information. In this paper, using the P.S.I.A.C model and capabilities of the GIS system, the lands belonging to Taham Chay basin are evaluated for erosion and sedimentation. For this purpose, the combination of PSIAC and GIS models can estimate the erosion severity and the amount of sediment produced in basins. Considering that topographic maps, slopes, directions and geology are all instrumental in determination of homogeneous units, these data were entered into the system's environment (GIS) as information layers, and after processing and organizing them, the classification and scoring of each of the effective factors in the intensity of erosion and sedimentation were carried out according to the P.S.I.A.C model. Finally, by summing up the scores of each of these layers, the final score is extracted, and based on this the intensity of erosion and sedimentation of the studied area is determined. According to the results of this research and previous experiments, this method can be used in areas where the erosion and sedimentation intensities are “low” to “very low”. Furthermore, in comparison to the amount of sediment obtained through the method in question with the actual amount measured in the hydrometric station set in the outlet of the basin, it was observed that the estimated result is in acceptable consistency with the measured values.

Diffusion means dissemination, expansion, dispersion and mixture. Hagerstrand considers the six factors of domain or environment, time, subject, origin, destination, and the path of the origin of phenomena and innovations as the main factors in Percolation Theory’s analysis of the process of geographic space. The study of geographical distribution of the Prophetic traditions can help us understand the conditions of origin and the quality of distribution of these traditions in time. The widespread dissemination of the Islamic Message, the Prophet's traditions and the life-style of the Prophet of Islam in the Arabian Peninsula and then in other parts of the world in the early centuries of Islamic civilization are considered by Muslim and non-Muslim geographers as a unique cultural phenomenon.

The inquiring mind of human being has always been looking for new and unique phenomena, and humans have undergone a great deal of suffering pursuing the recognition of unknown lands, and in fact they can be considered as the first tourists. Tourism is not a phenomenon peculiar to this day. It is a phenomenon that has long been considered by human societies, and has continued to advance in time according to different economic, social, historical and other needs. Tourism in today's world is pursued with various goals and objectives such as exchange of information and culture, increasing knowledge and awareness of past societies and spending leisure time, and it is becoming more and more valuable in economic, social and international structures. Domestic and foreign travels and, in parallel, formation of related activities in tourism competitions, will have many economic, political, social and cultural consequences for nations. According to information published by the World Tourism Organization W.T.O, today the tourism industry has become one of the most important economic sectors and, as a capable rival, is on the way to overcome industries such as oil, petrochemical and even automobile industry. In addition to economic aspects of tourism industry such as earning foreign exchange and ... the cultural, social and political aspects of tourism can be pointed out, which lead to closeness of nations and establishment of lasting peace in the world.

Prior to 1941, the Axis Powers were at height of their power. Almost all of Europe was occupied by Germany. The fate of Moscow and Stalingrad changed as a result of a small threat. Rommel (the German commander during the Second World War) was freely advancing in North Africa. The Japanese, with quick and simultaneous invasions in eight regions, achieved an astonishing position and, with this success, a new power emerged in Asia. The Japanese invasion of Pearl Harbor forced the Americans to fight against the Axis states. The American forces first entered the battle at the end of 1942 in North Africa. In the Battle of KASSRIN-PASS, the German Air Force, which was weaker than the US forces in terms of number of forces and equipment, carried out such heavy attack against them that led to their defeat. By analyzing this failure, the Americans came to the conclusion that their main mistake was lack of unity in command and control, as well as their lack of attention to multiple air forces controlled by numerous commanders, including many ground-force commanders. Command and control play very important roles in almost all societies. The advantages and disadvantages of their absence are well known. Command is assigned by commanders and applies to specific resources that usually include human resources. A person who is senior to a commander in terms of hierarchy, can monitor and control the resources that are under that commander’s authority. Therefore, control can be exercised by various organizations within an organizational hierarchical structure, depending on the task assigned to each of them, but command is only imposed by the official commander.

In short, in comparison, the accuracy of preparing maps by digital camera images is up to 2 times greater than the accuracy of maps based on photos produced by film on equal scale, and at the same time producing digital-image-based maps is significantly less time-consuming and costly

Box-Jenkins prediction model is one of the most famous time series models and is important in predicting different geographic phenomena. In Box-Jenkins methodology, time series models are in fact autoregressive integrated moving average models that are known as ARIMA models in statistics. Various models such as simple and multivariate regression, autoregressive, moving average, seasonal models and even unknown models can be derived from ARIMA models. In this research, while expressing the precipitation forecasting method using the Box-Jenkins time series model practically and by fitting this model on the monthly precipitation data of Ghaemshahr synoptic station, which contains statistics of 50 years, the best model for forecasting precipitation in this station was selected, which was from the type of SARIMA (1.0.1) (0.1. 1) model.

The Central Place Theory of Walter Christaller, a well-known German geographer, was first proposed in his 1933 book "Central Places in South Germany". The term central point or place is used to refer to a location that supplies goods and services to its surrounding areas, and is thus central to several areas and the source of their needs. In fact, this theory is designed to respond to the spatial distribution of cities and the systems of hierarchy among them, and the centrality of a site increases and decreases with corresponding increase and decrease in the level of service received by that location. In this paper, first the hypotheses and principles of the theory of Christaller are presented based on whose assumptions it can be said that in this theory all phenomena are placed in their ideal state, something that can be rarely found in reality. After assumptions, the urban hierarchy has been examined; according to his observations on central locations in southern Germany, Christaller found that there is a hierarchical system in the economic and administrative system of these central locations. His belief in the existence of a hierarchy among the central locations of the southern regions of Germany led him to classify them according to their population and degree of centrality. According to the Central Place Theory, the spatial distribution of central places takes shape in a regular geometric space that is displayed in the form of conventional and overlapping polygons (hexagons). After urban hierarchy, the concept of threshold and the concept of the sphere of influence of goods and services in the Central Location Theory, the factors affecting the return of consumers to the central location, the assessment of economic activities in a hierarchical system and the application of central places in regional planning are examined, and after reviewing these cases, Christaller’s theory has been evaluated, and finally a conclusion has been made.

Accidents occurring on highways in dense fog condition are often multi-vehicle collisions involving a dozen or sometimes hundreds of vehicles, resulting in casualties and financial losses. The same reason has attracted the attention of the mass media that demand the authorities explain about these conditions, as well as about the measures taken to reduce the effects of fogs. In this study, we have investigated the crashes in dense fog condition over a ten-year period. We have also examined deterrent measures in the Canadian structure of intelligent transportation systems.

The spatial databases created on the basis of a systemic structure have prepared the conditions that provide users with the possibility of communication and exploitation among remote sites through the World Wide Web. Websites provide access to a variety of information about land features in graphic and text documents. Global geographical databases are usually established and developed for various purposes. Perhaps software and information content will be continuously upgraded by using and expanding the database. Research on different aspects of the goals of global geographical databases requires other distinct studies. A brief overview of each of the bases is the topic of this paper.

By using coordinates of satellites and determining the receiver's distance from the satellite, the position of the GPS receiver is calculated and the distance is determined by measuring the time of the radio signal’s travel from satellite to receiver. But how are satellite coordinates determined and how is the time is measured? This is the topic of determining the satellite position and we know what it is and does, but we do not know how it works. In general, the determination of satellite position is a matter of triangulation. The receiver coordinates can be calculated by knowing the position of three satellites and measuring the distance between these satellites and the receiver. The distance between receiver and satellite is obtained by multiplying the radio signal’s travel time by the speed of waves (speed of light). But how we monitor the satellite's position permanently? The orbits of satellites can not be fully and accurately determined, and change by the effects of the forces imposed by celestial bodies. Since radio signals move at the speed of 300,000 km / s, inaccuracy in time measuring of the magnitude of one nanosecond leads to an error of 30 cm in distance measurement, while by using geometric receivers, precision of the order of magnitude of one centimeter can be achieved.