نشریه اطلاعات جغرافیایی (سپهر)
پیاپی 42 (تابستان 1381)

The Internet is a very important tool that has had a major role in receiving and disseminating information over the past few years. The Global Communication Network delivers and disseminates most of the recent news concerning geographic data. In this process, maps play a pivotal role and has a multi-purpose function. Maps can play their historical role in providing information for geographic plans and their necessary conditions. The main focus of the expansion of utilization is through the World Wide Web Group (WWW), and some problems regarding the supply of cartographic information have emerged as a result of this development. The most important issues are: - A wide variety of uncertain user environments - Uncertain Web Links (Connections)

The surface and in-depth marine topography of each ocean include continental shelf, continental slope, and deep islands and areas. Amphibious forces deal with marginal areas, especially coasts, approaches to the coasts and straits, while mariners are associated with mountain ranges, deep pits and vast plains hidden in the seabed.

Determining the difference between the elevations of points by geometric leveling method using leveling cameras is one of the most commonly used methods for implementation of developmental projects in the country. Implementation of projects such as preparation of longitudinal profiles of rivers, roads, power transmission lines, etc. requires leveling. In addition, this method is used in the implementation of nation-wide leveling networks and creation of base points (ground control) for converting aerial and satellite images into maps. Despite the extreme accuracy of the traditional leveling method, implementation of this method is time-consuming and costly, and so far no alternative has been considered by surveyors as feasible. The purpose of this study was to determine the relative accuracy of the GPS-based leveling method using the available Iranian Gravitational Geoid file in different parts of the country. The results of the research confirm the possibility of using this method to achieve the accuracy of normal leveling (of third degree) in most regions of the country.
 

The discussion about the desirable size of a city has long been considered by scholars and authorities of urban issues and has been analyzed in various aspects. In the 1960s and 1970s, this discussion found a special place in the literature on urban development and the attitudes toward this matter experienced significant changes. This issue has been of great importance as one of the major aspects of urban planning through several decades of urban planning in Iran. However, in recent years, due to the impact of the size of cities on certain governmental policies, people and city administrators have paid greater attention to this issue, which requires particular critique and analysis. In this brief article, it is tried to provide grounds for the development of thoughts and deepening of attitudes in this area by mentioning the views of relevant scholars.
 
 

Aerial photos contain details of land features. A photo interpreter systematically reviews photos and regularly utilizes other auxiliary materials, such as maps and field observation reports. According to this study, interpretation is carried out according to physical nature of features and phenomena on the photos. Interpretation may be implemented at different levels of complexity: from simple recognition of phenomena on the earth to extraction of detailed information, considering the complexity of the interactions between surface and subterranean features.

In this paper, the GLONASS system and its certain aspects that affect the positioning of the carrier phase are examined and the current state of the GLONASS system has been considered. The results show that positioning can be achieved using the GLONASS carrier phase, and the combined use of both GLONASS and GPS systems has valuable advantages in comparison with the use of the GPS system alone.

Flood means a sudden overflow of water due to hydro-climatic and hydrological conditions, severe rains, and damages to dams in different areas of the earth. Evidence suggests that life and financial losses caused by flood are more than other natural disasters. Today the estimation of maximum flood and its prediction before occurrence are among the important issues discussed in hydrology; nevertheless, with increasing population growth and development of industry and the subsequent occupation of the lands adjacent to rivers, the losses caused by flood have not only not diminished, but are constantly increasing. What is certain is that flood is caused by rain, but studies show that there is no linear and direct relationship between these two factors. Climate, natural and geographical conditions of a region are among the main factors that contribute to the disruption of this relationship.

Although our universe and all objects in it are three-dimensional (3D), nonetheless commercial GIS usually reduces spatial data (spatial data) to two-dimensional (2D) due to different data considerations. If the entire range of the known applications of 2D GIS is to become available in a 3D GIS, certain appropriate topological and geometric information structures become necessary. The author of this article reviews the current problems of access to 3D GIS and provides answers that result from his research efforts.

The magnificent Saturn, the sixth planet in terms of distance from the Sun, is the furthest known area of the ancient times, moving at a low speed around the Zodiac. Ancient Greeks have introduced this planet as Kronos, the father of Zeus, because in these stories Saturn is named after the god of planting and seeding. The ancient Greeks associated the Saturn with the ancient god of time, later the father of time. The Saturn revolves around the Sun at a distance of 9.5 AU, with an orbital period of 29.5 years. The name of the planet has been adapted from the word Saturnine, meaning heavy and made of lead, to describe its great cold and large atmosphere, which is probably due to its smooth motion throughout the orbit.

Firoozabad is one of the cities of Fars province in southern Iran where environmental management has received less attention. In this paper, using the method of studying land systems, the factors affecting the current appearance of these systems are identified and the role of humans in degradation of the environment, intensification of erosion and change in the appearance of Firouzabad environment have been determined. At the end, suggestions have been made to improve the environmental management methods in the studied area.

The city of Babolsar is a new city still influenced by traditions of a rural culture; it has nevertheless grown considerably over the past hundred years and cannot be considered as a rural fortress anymore. It has mainly grown in a wild manner in low areas surrounding it. In general, three major factors including the sea, river and road network have had direct impact on the physical and spatial development of Babolsar. The great number of young population and the excessive migration of villagers to Babolsar are among major problems of the city. This will certainly delay the process of development, and it is not unexpected that the city reach a critical level of population. It is necessary to deal with this important issue based on accurate planning, including birth control and demographic policies, development of rural facilities and capabilities, and strengthening of small urban centers around Bablosar.

Most employers, whether they belong to public or private sections, have more or less a clear picture of what they want to implement. They often cannot properly convey their wishes to the people who are to carry them out. At this stage, the need for consultant engineering services who have capable experts in employment becomes clear. The above-mentioned relationship between employer and consultant has almost the same nature in Europe and other countries, with the difference that in non-European countries the consultant and the employer are usually of different nationalities and it is their historical past that links them together.

Nowadays new (alternative) energies are paid significant attention by most countries of the world in the pursuit of goals such as environmental protection, sustainability of energy resources and continuous use of permanent energies. Due to the huge technical differences among the countries of the world, much of the production and use of this kind of energy is also available to advanced countries. Nevertheless, the Third World countries also try to gain the right status in production of alternative energies by relying more or less on energy sources such as wind, solar, geothermal, nuclear, and electrical energies.

Ecotourism is a type of tourism that emphasizes natural attractions (Edington Ecotourism, 1995), and which needs, above all else, to establish a relationship between human and nature, especially in certain areas of the planet where nature shows a harsher face. Therefore, in this article, the necessity and manner of this relationship and the effective role of man in this regard have been considered, and by studying the climate as one of the most important factors in the environment, the climatic characteristics of the Polar Regions have been examined in terms of specific conditions caused by them in tourism industry. Finally, we have studied ice hotels as the best example of using one of the world's most violent natural environments as tourist attractions. This example can be a model for territories that have a violent and different character of nature.