Mahmoud Khosravi
Volume 9, Issue 34 , August 2000, , Pages 56-64
Abstract
Tourism industry is considered as one of the most important activities in the contemporary world. Every year there are 1.7 billion tourist travels which cost about $600 billion. The incomes of some countries such as Tunisia and Bahama are provided by tourism industry. Unfortunately, Iran’s share ...
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Tourism industry is considered as one of the most important activities in the contemporary world. Every year there are 1.7 billion tourist travels which cost about $600 billion. The incomes of some countries such as Tunisia and Bahama are provided by tourism industry. Unfortunately, Iran’s share of this industry is less than $200 million. On the whole, there is no doubt that climate is the main cause of the seasonal characteristic of tourism. In this paper, after examining major points and analysis of some models of tourist regions’ assessment, epistemological limitations of tourism studies are discussed. One of the most difficult stages is modeling the future climate. Assessment of the effect of climate on tourism is a sensitive and multi-faceted task. Considering the need for evidential research, we face many questions that need to be answered. Our main goal in this paper is to provide such answers. Today, there are evidences that in activities regarding the effect of climate, the mutual effects of environment and human are also considered. Therefore, the present article has also discussed the possibilities and limitations of research concerning climate effects on tourism. In this paper, first the importance of tourism-climate issues are discussed, and then a comprehensive examination of epistemological matters concerning climate effect research has been presented; finally, strategies for more advanced research about climate effects on tourism have been proposed.
Mohammad Hasan Ganjii
Volume 1, Issue 4 , May 1992, , Pages 56-60
Abstract
In the third issue of Sepehr, we presented a discussion about the shape of the Earth and its hypothetical divisions (orbits and meridians), and the importance of each one. Before we go into the discussion of the movements of the Earth, it will not be out of place if we first obtain brief information ...
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In the third issue of Sepehr, we presented a discussion about the shape of the Earth and its hypothetical divisions (orbits and meridians), and the importance of each one. Before we go into the discussion of the movements of the Earth, it will not be out of place if we first obtain brief information about the Earth in space, as understanding of many geographic concepts will relate to this information.
For centuries, man thought that Earth was the center of the universe, but today's man has gained amazing information about the universe. It is now assumed that our Earth is a small planet that moves along eight other planets around the Sun, and the Sun is a star that moves with thousands of other stars in a galaxy among millions of galaxies in an infinite universe.
Shokrallah Mohammadi
Volume 8, Issue 30 , August 1999, , Pages 57-58
Abstract
Today, with advances and development of computer technology, many firms and organizations which practice map preparation have turned to conversion of manual system (manual cartography) to computer system (digital cartography). Currently all stages of manual cartography are carried out using computers, ...
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Today, with advances and development of computer technology, many firms and organizations which practice map preparation have turned to conversion of manual system (manual cartography) to computer system (digital cartography). Currently all stages of manual cartography are carried out using computers, which leads to increase of the speed of cartographic operation, achievement of top quality at stages of work and reduction of map preparation costs.In this paper, the Raster and Vector information in creation of cartographic images as well as advantages and disadvantages of these images and their method of processing are examined.
Fereshteh Tavakkoli
Volume 12, Issue 45 , May 2003, , Pages 58-61
Abstract
The purpose of geological studies is to identify water-containing layers and basin reservoirs, as well as to determine the tectonic and geological structure of the area. In general, the Aligudarz plain and its southern highlands are located at the site of the major geological structural unit of Iran, ...
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The purpose of geological studies is to identify water-containing layers and basin reservoirs, as well as to determine the tectonic and geological structure of the area. In general, the Aligudarz plain and its southern highlands are located at the site of the major geological structural unit of Iran, so that it is bounded on the north to Sanandaj and Sirjan and on the southwest to Oshtorankooh, which is part of the High Zagros. Considering the geologically and structurally special location of the site, two examples are briefly described.
Hasan Shamsi
Volume 1, Issue 1 , May 1990, , Pages 58-64
Abstract
During the Second World War, radar was used to detect objects or targets and to determine their distance and direction (or azimuth).
The radar performs its task by sending extremely short waves (called microwaves) to a target and their return from the target to the sender. The total traveling time ...
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During the Second World War, radar was used to detect objects or targets and to determine their distance and direction (or azimuth).
The radar performs its task by sending extremely short waves (called microwaves) to a target and their return from the target to the sender. The total traveling time of these waves, shown on their indicator, determines the distance between the sender and the target.
After World War II, especially in recent decades, designers and makers of surveying and geodetic instruments such as Wild, Kern, Zeiss, AGA, So-kisha, and American K.6 have recognized the use and application of electromagnetic waves in surveying and geodesy, and began to develop electronic and electro-optical space measurers as well as tellurometers. In the first paper from this series of articles, we introduce electromagnetic and radio waves.
Bahman Ramezani Gourabi
Volume 20, Issue 78 , August 2011, , Pages 59-65
Abstract
Marginal areas and islands of the Persian Gulf are located in a warm and humid climate with high absolute humidity; areas with an unfavorable climate among whose characteristics are minimum precipitation and water shortage, abundant water vapor, low relative humidity, high radiation levels , Dust, … ...
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Marginal areas and islands of the Persian Gulf are located in a warm and humid climate with high absolute humidity; areas with an unfavorable climate among whose characteristics are minimum precipitation and water shortage, abundant water vapor, low relative humidity, high radiation levels , Dust, … , which, considering urban development plans and the creation of new towns and industrial areas associated with increase in population, are of great importance in terms of energy costs in an unfavorable climate. In the past, indigenous people provided more or less tolerable conditions due to the presence of Hara forest vegetation and the use of indigenous techniques against undesirable climate. However, due to new structural changes, this approach is accompanied by the Increasing cost of energy over the year. The purpose of this paper is to identify the potential of creating desirable climatic conditions in Hara forests in the Persian Gulf, with an emphasis on reducing energy costs. The method of research is descriptive-analytical, using existing statistics of meteorology and application of bioclimatic human models. This article tries to introduce the development and understanding of these forests as one of the ways to create the optimal local and regional climate in the Persian Gulf region for the desirable human development, so that vegetation is preserved in the UAE in the southern region of Persian Gulf with great costs, while in the northern regions of the Persian Gulf (Iranian section), this potential can be developed at the lowest cost in the margins and islands, in which terms it is incomparable with the south.
Mohammad Reza Zand Moghaddam
Volume 13, Issue 52 , February 2004, , Pages 59-60
Abstract
“Geography is the science of places”, “Geography is the science of connections”, “Geography is the science of human ecology”, “Geography is the science of dispersion”, and “Geography is the science of mutual relations”... are all the beautiful ...
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“Geography is the science of places”, “Geography is the science of connections”, “Geography is the science of human ecology”, “Geography is the science of dispersion”, and “Geography is the science of mutual relations”... are all the beautiful definitions of geography that have been expressed by the great scientists of this science, such as Vidal de La Blache, Griffith Taylor, etc. Each of the above definitions, while in the simplest form of expression, has certain complexities, which, after stating causes of various factors, has established the foundations of geography, and has been interpreted by geographic associations all over the world, and has been the founder of many thoughts and ideas that made a significant contribution to the advancement of geography in the world, so that in addition to the advancement of this beautiful human knowledge, it caused certain followers each explain the old ways and try to contribute to the progress of thoughts through critique and evaluation. However, from another perspective, the abovementioned scholars were not only the founders of a new tradition, but also helped their followers in their respective countries and in other countries to benefit from it and promote their thoughts, especially in their country, and this fact has been developing the science of geography in these countries and providing the ground for scientific advancement and other aspects of domination over the world both scientifically and colonially. In this paper, we try to recognize our share in geography and to know what geographic dominant ideas exist in our country? Or, with what point of view, a better and more appropriate thought can be chosen for the geography of Iran. With a brief look at geography in Iran, we will find that this science, along with the progress of other sciences in the world of Islam, was properly cultivated during this period, and the scholars of the Balkh and Iraqi schools, each with their own interpretations, made significant contributions to the flourishing of this era, even by writing the geography through pilgrimage literature.
Mohmmad Javad Dadrast
Volume 9, Issue 35 , November 2000, , Pages 59-64
Abstract
The need for robust and advanced support of information processing in planning (due to the volume of data and the growth of number of users) makes efficient and powerful systems of information processing inevitable. GIS, or Geographic Information System, with the special feature of combining spatial ...
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The need for robust and advanced support of information processing in planning (due to the volume of data and the growth of number of users) makes efficient and powerful systems of information processing inevitable. GIS, or Geographic Information System, with the special feature of combining spatial and non-spatial data, has gained a special status among managers and planners.
Ramin Kiamehr
Volume 15, Issue 58 , August 2006, , Pages 60-64
Abstract
Since 1986 several gravimetric geoid models were published in the Iran region. Based on primary investigation on these gravimetric geoid models, it is found that their relative and absolute accuracies versus GPS/levelling are more or less the same or in some cases worse than the current available global ...
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Since 1986 several gravimetric geoid models were published in the Iran region. Based on primary investigation on these gravimetric geoid models, it is found that their relative and absolute accuracies versus GPS/levelling are more or less the same or in some cases worse than the current available global geopotential models (Kiamehr 1997,2003 ,2001a , 2003b, 2004 and Kiamehr and Sjöberg 2004). Regardless the effect of choosing proper computational method in determination of any geoid models, the quantity and quality of the gravity anomaly database plays a major rule in the final result of them. The main aim of this research is the creation of a more complete and also refined new gravity database for Iran. For this purpose different dataset from different sources are gathered and combined in a single database. Then we start to refine it from possible outliers by using Least Squares Collocation (LSC) approach. A special method used for the interpolation scheme of free-air gravity anomalies in order to take into account the effect of topography. The final grid file was creates based on the Kriging method with 80" * 90" resolution. The overall accuracy for the current database is estimated to near 10 mGal.
Reza Arab Sahebi
Volume 14, Issue 55 , November 2005, , Pages 60-64
Abstract
Geodesy is a science that is related to determining the shape and geometry of the Earth and coordinates of points on the surface of, and above, the Earth, such as satellites and other moving objects above the Earth's surface. Therefore, in order to meet the geodesic goals in regards to positioning, we ...
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Geodesy is a science that is related to determining the shape and geometry of the Earth and coordinates of points on the surface of, and above, the Earth, such as satellites and other moving objects above the Earth's surface. Therefore, in order to meet the geodesic goals in regards to positioning, we first need to define the geodesic-related coordinate system. In order to be able to objectify a point in three-dimensional space and to express its relation to a reference system called the coordinate system, we need to specify three parameters: 1 - origin 2 - axis directions 3 - parameters defining the position of a point in the coordinates system. One of the systems used in geodesy is the geocentric coordinate system, the origin of which is a point near the center of the Earth and the Z axis of the system is along the Earth's axis of rotation. Since the Earth's rotation is around the pole and the location of the pole is variable, the Z axis will have a different position, therefore we find it difficult to find the parameters determining a certain position in this system (factor III of the definition of the coordinate system). In this paper, using observations regarding the x, y components of the pole from 1962 to 1997, it can be concluded that this non-periodic motion can be studied and even predicted by using mathematical methods through the fitting of continuous functions. The results show that the power of showing this important movement in various mathematical functions is different, so that in some mathematical functions, the polar motion has an incremental acceleration, while others show that this movement has a completely irregular acceleration.
Alireza Azmudeh Ardalaan (Translation)
Volume 1, Issue 2 , February 1990, , Pages 60-62
Abstract
As the accuracy of observed angles and lengths is one of the main factors in the final accuracy of a mapping task, the justification of network also plays a major role here. The justification of network according to the real north is a simple task and has many advantages. If this operation (network justification) ...
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As the accuracy of observed angles and lengths is one of the main factors in the final accuracy of a mapping task, the justification of network also plays a major role here. The justification of network according to the real north is a simple task and has many advantages. If this operation (network justification) is performed through astronomical observations, the mapper must be aware of all sources of error in the justification of network and understand that even if the lengths and angles are accurately measured, the existence of error in justification of network can reduce the final accuracy. In this paper, that source of error is discussed which has not yet received the attention it deserves, and a field approach has been proposed to eliminate this error.
Mohammad Ekhbari; Abolfazl Ranjbar; Seyyed Mohammad Bagher Fatemi
Volume 15, Issue 59 , November 2006, , Pages 61-64
Abstract
Data extraction from satellite images has significantly developed in recent decades, and various algorithms have been introduced to extract information from satellite imagery, each of which has advantages and disadvantages. In general, the methods of classification of satellite images fall into ...
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Data extraction from satellite images has significantly developed in recent decades, and various algorithms have been introduced to extract information from satellite imagery, each of which has advantages and disadvantages. In general, the methods of classification of satellite images fall into two types of supervised and unsupervised classifications. Furthermore, supervised classification methods are divided into two parametric and non-parametric methods. In this paper, the purpose is to introduce and study the algorithms of parametric supervised and unsupervised classifications of satellite images in terms of accuracy and method of extracting information. Finally, by comparing the algorithms of the existing methods, we conclude that the method of maximal similarity is more accurate than the minimum distance and parallelepiped methods, but it is still not possible to achieve the desirable precision in classification using this method. In fact, statistical methods such as maximal similarity can not be used if the goal is acquiring high precision, because the method of maximal similarity is a completely statistical method, and therefore, it can not provide the ability to accept and use external information in a non-statistical form such as geometry of imaging, geometry of features whose images are being taken, as well as effective factors such as the atmosphere in the classification process, and this is one of the weaknesses of maximal similarity classification in comparison to model-based methods. Therefore, methods such as model-based and science-based have been introduced to improve this method and eliminate its problems.
Zohreh Merianji; Reza Borhani
Volume 12, Issue 47 , November 2003, , Pages 61-64
Abstract
Climate change is a general term that describes climatic discontinuity and rupture. In order to study temperature changes in Hamadan, temperature fluctuations in a statistical period of fifty years (1952-2002) have been investigated. According to a survey conducted in 1973, a sudden drop in the minimum, ...
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Climate change is a general term that describes climatic discontinuity and rupture. In order to study temperature changes in Hamadan, temperature fluctuations in a statistical period of fifty years (1952-2002) have been investigated. According to a survey conducted in 1973, a sudden drop in the minimum, and a sudden rise in the maximum, temperature were observed. According to the Mann Kendall test, there are significant changes in the three parameters of minimum, maximum and average temperature, including the decreasing trend observed in 1962, and this negative trend continued until 1992, and this year thereafter, an increasing trend of temperature can be observed. It should be noted that the maximum spring temperature is an exception, since in the year 1992 it is the beginning of cooling season. On the minimum temperature chart, the falling trend starts from 1957 and continues until 1974. The result is that the year 1992 is the beginning of a period of increasing temperature and climate change in Hamedan, and the temperature rise is 0.55 degrees averagely, 0.79 ° C at minimum temperature and 0.3 ° C at maximum temperature.
Volume 16, Issue 61 , May 2007, , Pages 61-62
Abstract
Introducing the book " Thermal remote sensing and its application in geosciences".
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Introducing the book " Thermal remote sensing and its application in geosciences".
Majid Mokhtarani
Volume 12, Issue 48 , February 2003, , Pages 62-64
Abstract
The system in discussion is a new tool and capability on the SPOTS satellite sensor, which we were eagerly waiting for. SPOT IMAGE and its partners have gained very good resultsout of this key innovation for customers of Digital Elevation Models (DEM) and geometrically corrected images with appropriate ...
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The system in discussion is a new tool and capability on the SPOTS satellite sensor, which we were eagerly waiting for. SPOT IMAGE and its partners have gained very good resultsout of this key innovation for customers of Digital Elevation Models (DEM) and geometrically corrected images with appropriate precision. On the SPOTS satellite a system called High Resolution Stereoscopic (HRS) was designed over a period of five years for creation of a Digital Elevation Model (DEM) for a coverage of 30 to 50 million square meters (one-third of the earth’s drylands).HRS is able to provide almost simultaneous topographic (stereo) images from very large areas.Its coverage is 120x600 km at every passage of satellite. This sensor will provide 126,000 square kilometers of coverage stereo images in just one day.This remarkable ability to provide stereo images at the same time is a step forward, not only for production of a digital elevation model (DEM) in vast areas and topographic maps, but also for automatic production of vertical images with very high geometric precision.
Iraj Jabbari (Translator)
Volume 12, Issue 46 , August 2003, , Pages 62-64
Abstract
The geomorphology engineering is the application of the principles of geology to solve the river engineering problems. The process-based understanding of the problem makes it possible that an engineering solution be implemented in parallel with evolution of system rather than imposing it on the system.Increasing ...
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The geomorphology engineering is the application of the principles of geology to solve the river engineering problems. The process-based understanding of the problem makes it possible that an engineering solution be implemented in parallel with evolution of system rather than imposing it on the system.Increasing the chances of success, reducing costs and decreasing the probability of a problem being uselessly circulated within the system are among the benefits of this view.
Fatemeh Razi'ei (Translator)
Volume 8, Issue 31 , November 2009, , Pages 62-64
Abstract
Geo-informatics is defined as a multi-purpose science dealing with measurement, recording, analysis and presentation of geographical data. Such land information is collected by RS, GIS and GPS. Each one of these three technologies, or each two of them, when combined with the other, create the new 3S ...
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Geo-informatics is defined as a multi-purpose science dealing with measurement, recording, analysis and presentation of geographical data. Such land information is collected by RS, GIS and GPS. Each one of these three technologies, or each two of them, when combined with the other, create the new 3S technology.Remote sensing provides images of environment and natural resources in a multi-spectral manner and with different resolutions in different times. GPS and also INS (Inertial Navigation System) reinforce the applied sensors through ground control points and photogrammetry. GIS deals with data and information taken by the help of modern tools from ground spatial data banks and bases which make decision-making possible.
Hushang Pulaki
Volume 1, Issue 3 , August 1991, , Pages 62-64
Abstract
One of the most important tasks of topographic maps is to show the nature in lifelike manner. Today, this is done in a variety of ways, such as shading the contour line, which in some cases is very difficult. Of course, this method is quick, but to some extent it has the weakness that it does not display ...
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One of the most important tasks of topographic maps is to show the nature in lifelike manner. Today, this is done in a variety of ways, such as shading the contour line, which in some cases is very difficult. Of course, this method is quick, but to some extent it has the weakness that it does not display the raised quality of certain points with acceptable quality.
In order to obtain the natural state of the Earth, research has been carried out which prove the superiority of the 3D view available in topographic map.
One of the most familiar and prominent types of these maps is the typical topographic maps (raised surfaces). In this case, the map will be raised on a plastic foil and with the help of heat. This map will face changes (movements of points on it) due to later changes in the foil, in a way that that this change will become greater as the height of the feature increases.
Mojtaba Fathi; Alireza Ma'manpush
Volume 18, Issue 72 , February 2010, , Pages 71-74
Abstract
Achieving stable agricultural production with proper profitability and, at the same time, preserving the environment from destructive effects of chemical fertilizers is not possible without taking the changes in farm’s soil and plant growth into account. The division of the farm into management ...
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Achieving stable agricultural production with proper profitability and, at the same time, preserving the environment from destructive effects of chemical fertilizers is not possible without taking the changes in farm’s soil and plant growth into account. The division of the farm into management sections is carried out in a variety of ways. Concentrated sampling of plants and soil, preparation of contour line maps of its features, and the use of aerial (installed on airplanes) and satellite sensors are among these methods. In developing countries, access to high resolution satellite data is not feasible due to economic and security reasons. However, satellite data with smaller scale is partially able to make the division of the management sections in the farm according to the state of plant growth possible. In this study, the possibility of dividing in-farm management sections based on the NDVI index calculated from the reflection intensity at Landsat 7 satellite wavelengths has been investigated. The NDVI map provides the possibility of dividing farm sections, calculation of the cropping area of each product, and the division of sections with different growth. The coefficient of variation of the NDVI growth index in the 10 hectare farm scale was about 11.5% and was significant. The observable growth rate of the field and the growth rate estimated according to the NDVI index field show agreement.
Habibollah Fasihi
Volume 16, Issue 62 , August 2007, , Pages 71-73
Abstract
Earthquake is part of the Earth’s natural behavior, occurring more than 150,000 times a year, but only a small number of them are associated with life and financial dangers and losses. Humanity has long been struggling with this phenomenon and has been horrified by it. There have been many human ...
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Earthquake is part of the Earth’s natural behavior, occurring more than 150,000 times a year, but only a small number of them are associated with life and financial dangers and losses. Humanity has long been struggling with this phenomenon and has been horrified by it. There have been many human settlements destroyed by the earthquake and their inhabitants immediately buried and annihilated under the debris. Unlike other natural hazards, earthquakes take place on a vast territory and bring about widespread damage and destruction. The sudden occurrence of earthquake and its unpredictability and the inability of man to control this phenomenon are also among the causes of human panic even in our time. Today, humans have been able to partly protect themselves from earthquake hazards by the construction of earthquake-resistant buildings. Although earthquakes might occur on any point of the earth, but the research suggests that it is more likely in the vicinity of active faults and therefore the severity and damage of earthquake is also more serious in these areas, because the concentration of energy inside the earth causes the flaws to move and take on a new state resulting in an earthquake. Ray is one of the ancient cities of Iran which, due to its proximity to active faults, has great potential for earthquake occurrence and has therefore suffered many devastating earthquakes causing a lot of damage and casualties throughout the course of history. The present paper first reviews the history of Ray’s earthquakes and then examines the probabilities of earthquake occurrence according to the location of faults.
Ezzatollah Ghasemifar; Siamak Taghizadeh
Volume 22, SEPEHR , July 2013, , Pages 74-82
Abstract
Borderline areas are very important and influential in the development of country and underdevelopment in these areas will be directly transferred to the whole country. Sistan-va Balushectan is a borderline area in Iran which lack an appropriate developmental status. In sum, major challenges facing Sistan-va ...
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Borderline areas are very important and influential in the development of country and underdevelopment in these areas will be directly transferred to the whole country. Sistan-va Balushectan is a borderline area in Iran which lack an appropriate developmental status. In sum, major challenges facing Sistan-va Baluchestan includes:
Geographical broadness with limited population (178431 km2 with a population of 1722579-Statistical center of Iran: 2006), long and insecure borders, natural obstacles like deserts, lack of natural blessings, geographic isolation, geomorphological factors, climatic situation and lack of oil and gas resources, settlement of Baluch tribes in both sides of the border, vicinity to Pakistan and Afghanistan, instability and weakness in providing complete political, administrational and economic sustainability which have resulted in lack of control on borderlines, political flow of Afghan refugees, vicinity to the largest drug producer and smuggler entering Iran through Sistan va Baluchestan borders, economic, cultural and social inequalities in this area as compared to central areas, poverty and deprivation which have resulted in a tendency toward smuggling. These challenges have resulted in numerous and various problems and issues which can threaten local, regional and even national development. If the present situation continuous, more severe difficulties can arouse. Therefore, the present article seeks to understand geopolitical features as an effective factor in underdevelopment of Sistan-va Baluchestan to gain a research-based perspective and create the foundations of sustainable development in the area.
Alireza Abbasi Semnani; Hojjat Mahkouii
Volume 20, Issue 77 , May 2011, , Pages 74-79
Abstract
Most people have ambiguous perceptions of geography. Many people think of geography as a science that merely studies mountains, rivers and nature. But since geography was introduced as a science and academic discipline and has played an important role in the advancement and development of places, different ...
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Most people have ambiguous perceptions of geography. Many people think of geography as a science that merely studies mountains, rivers and nature. But since geography was introduced as a science and academic discipline and has played an important role in the advancement and development of places, different views on geography have emerged among people. This scientific discipline has two main dimensions, namely, nature and man. These two dimensions mutually affect each other. In the human dimension, both men and women have important and major roles in affecting and being affected by the nature. Considering this fact, the role of gender in geography is emphasized, which has made one of the branches of geography, geography of gender, to be paid significant attention to by scientific and academic circles.Therefore, considering the role that human beings play in the development and planning of a geographic location, this role has been viewed as a unilateral and one-dimensional role in most societies, and women have not been as influential as men in gaining important occupations and influencing the planning process for development. Although in some countries they have obtained a significant role thanks to liberal democracy, they are still lagging behind in most societies. The purpose of this research is to investigate the role of gender and its impact on the advancement and development of societies. This paper has been carried out by descriptive-analytical method and the findings of the research are obtained by reviewing library documents. The main question in this article is: Is equality of sexes considered in geographic development of places? And its main hypothesis: equality between the two sexes (men and women) has a diminishing value and credibility in the geography of places.
Fatemeh Dehghannejad
Volume 21, Issue 81 , April 2012, , Pages 76-79
Hamid Kamrani Dalir
Volume 15, Issue 60 , February 2006, , Pages 76-79
Abstract
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 ...
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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.
Mohammad Mahdi Hoseinzadeh; Saeed Rahimi Harabadi
Volume 22, Issue 87 , November 2013, , Pages 77-80
Abstract
Exploring the changing processes of land forms is considered to be one of the key topics in geomorphological studies. Nowadays, geomorphological studies analyzes and clarifies geomorphic forms and processes at ground level. This shows the dominance of a systematic view in this field. In systematic view, ...
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Exploring the changing processes of land forms is considered to be one of the key topics in geomorphological studies. Nowadays, geomorphological studies analyzes and clarifies geomorphic forms and processes at ground level. This shows the dominance of a systematic view in this field. In systematic view, geomorphic analyses are performed based on the relation between land form and process. Geomorphologic threshold is one of the key concepts in systematic theory and thus is of significant importance in geomorphology. It indicates borderline situations during the occurrence of changes and shows temporal changes. The present article is based on secondary research and exploits theoretical and applied concepts related to thresholds, seeking to reach a balanced systematic analysis. It tries to study geomorphologic thresholds and classifications using different Persian and English resources. Moreover, we propose a short overview of some geomorphological issues, such as gully erosion, alluvial fan and river systems. Results indicate that geomorphic thresholds separates different situations of a system and are thus distinguishable. In fact, occurrence of a threshold changes the dominant processes in a geomorphologic system. This concept shows the situation in which a process operates to establish a new balance in the system. Siyum classifies geomorphic thresholds into two categories: 1) Internal which is related to the inside of a geomorphic system and 2)external which is under the influence of external variables such as climatic and tectonic changes.
