Mahdi Modiri
Volume 5, Issue 20 , February 1996, Pages 2-3
Abstract
In the map and image printing process, several factors contribute to the reduction of accuracy and esthetic appeal. In fine print works, half-tone points have a diameter of about 0.2 millimeters; these points, like many small objects, undergo deformation and gain complexity on the big-world, human and ...
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In the map and image printing process, several factors contribute to the reduction of accuracy and esthetic appeal. In fine print works, half-tone points have a diameter of about 0.2 millimeters; these points, like many small objects, undergo deformation and gain complexity on the big-world, human and physical scales. When pixels and half-tone points are transmitted from address network to print page, mathematical shapes are affected by physical machines. Lithography, printing process and mechanical complications are also added. These disturbances affect the final image, and the degree of this effect depends on the nature of the half-tone structure, the nature of the image and the physical process.
In order to avoid any increase of half-tone disadvantages, awareness of the factors affecting the image is necessary. Here the various sections of the common method are reviewed briefly.
Rahim Sarvar
Volume 5, Issue 20 , February 1996, Pages 4-15
Abstract
Today regional imbalances within the national space have made it necessary to investigate urban network and hierarchy system in order to address the factors affecting the location of cities, the pattern of distribution of urban population and, finally, the balance and imbalance in the urban hierarchy ...
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Today regional imbalances within the national space have made it necessary to investigate urban network and hierarchy system in order to address the factors affecting the location of cities, the pattern of distribution of urban population and, finally, the balance and imbalance in the urban hierarchy system of each region, and suggest solutions based on the knowledge of the status quo. The purpose of this paper is to investigate the spatial distribution of population and the balance of the urban hierarchy system in the southern coast of Iran. In this paper, first the position and natural characteristics of the region are introduced, and then the location of cities, urban population developments, spatial distribution and pattern of urban population dispersion are studied, and finally the urban hierarchy system is considered.
Abbasali Salehabadi (Translator)
Volume 5, Issue 20 , February 1996, Pages 16-19
Abstract
Absolute positioning is the use of a unique GPS receiver. In the instantaneous measurement and processing of GPS data, accuracy of positioning of points is limited by errors such as those of satellite orbit, the deliberate S.A noise, effects of propagation of carrier waves in the receiver's environment ...
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Absolute positioning is the use of a unique GPS receiver. In the instantaneous measurement and processing of GPS data, accuracy of positioning of points is limited by errors such as those of satellite orbit, the deliberate S.A noise, effects of propagation of carrier waves in the receiver's environment and errors due to the reflection of waves from convex and polished surfaces. Usually in such situations the accuracy of absolute positioning in the direction of horizontal components is about 100 meters (at the confidence level of 95% errors) and in the altitude component about 156 meters. Major errors are mostly due to satellite orbits or deliberate S.A. noise. S.A. is a method by which the satellite control stations intentionally transmit an orbital error of about 100 meters to satellites, which limits the desirable accuracy of access for GPS users when determining absolute and instantaneous position using the technology mentioned above.
To solve this problem, we need to have accurate orbital parameters as well as corrections for the satellite clock (time). Only a certain number of government agencies have access to such parameters, so we can have access to satellite clock’s corrections (for implementation of accurate interpolation calculations) for just a short time. Due to rapid changes in satellite clock’s error owing to the implementation of S.A., we always need to know the corrections related to constant positioning. The Geodetic Mapping Unit of the Canadian National Resources Agency is one of the first governmental organizations that produces such information according to a general principle.
In order to gain a good level of accuracy by utilizing constant positioning information, in November 1993 the first experimental trip of a marine vessel without a coastal navigator was conducted with the aim of examining GPS positioning. The results of this experiment are summarized below.
Mahdi Modiri
Volume 5, Issue 20 , February 1996, Pages 20-25
Abstract
Remote sensing is a science that provides valuable information on objects and land features by measuring distances from afar and without physical contact.
In remote sensing, information can be obtained by measuring and recording the reflections of electromagnetic waves of atmosphere and ground level, ...
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Remote sensing is a science that provides valuable information on objects and land features by measuring distances from afar and without physical contact.
In remote sensing, information can be obtained by measuring and recording the reflections of electromagnetic waves of atmosphere and ground level, which are received by sensors installed on satellites, and after their analysis, the necessary information is extracted.
There are three major factors of reflection, absorption and passage in the collision of electromagnetic waves with any phenomenon, each of which depends on the wavelength of radiated energy and physical and chemical properties of the phenomenon, and the energy reflection from any phenomenon on the Earth is a function of wavelength, molecular and intracellular properties of the phenomenon and other physical characteristics of the objects under measurement. The satellite data originally contains various geometric and radiometric errors that are affected by satellite, sensor and atmospheric conditions, as well as errors in recording, transmission of information and other related issues.
Satellite data become valuable and useful after making geometric and radiometric corrections. By performing geometric corrections, satellite information is readily to for analysis and utilization.
Abbas Khosravi
Volume 5, Issue 20 , February 1996, Pages 26-34
Abstract
The vast country of Iran offers great opportunities for conducting geomorphological studies due to its rare climatic variety and arid and semi-arid closed basins. Landforms and their beautiful landscapes call for unrelenting explorations of researchers to disclose unknown secrets. Over the past few decades, ...
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The vast country of Iran offers great opportunities for conducting geomorphological studies due to its rare climatic variety and arid and semi-arid closed basins. Landforms and their beautiful landscapes call for unrelenting explorations of researchers to disclose unknown secrets. Over the past few decades, valuable studies have been conducted by Iranian geomorphologists on characteristics of arid and semi-arid closed basins of the country. However, the quantity of these investigations and the low number of their related publications has caused many researchers in the field of geosciences to lack the due knowledge of geomorphological features of closed basins of arid areas. This paper is the result of an effort to introduce some of the geomorphological features of the Saghand Hole.
Masoud Mo'ayyeri
Volume 5, Issue 20 , February 1996, Pages 35-44
Abstract
There are more than thirteen thouasand volcanos on the surface of earth. Any volcanic crater or set of craters close together are called a volcanic system for past eruptions.
Volcanic manifestations can be identified as Magma, which has been formed during volcanic activities and then gradually cooled ...
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There are more than thirteen thouasand volcanos on the surface of earth. Any volcanic crater or set of craters close together are called a volcanic system for past eruptions.
Volcanic manifestations can be identified as Magma, which has been formed during volcanic activities and then gradually cooled down. In some cases, these activities have continued for centuries, like the Etna Volcano in Italy, and in other cases they lasted only for a few hours, like the Niracongo in Zaire in 1977.
Fatemeh Razi'ee (Translator)
Volume 5, Issue 20 , February 1996, Pages 45-50
Abstract
This paper discusses the main aspects of automatic transfer of points as a basis for determination of justification parameters of digital images. The selection of points, techniques of forming digital models, role of approximate values, structure of image and existing conditions have been discussed, ...
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This paper discusses the main aspects of automatic transfer of points as a basis for determination of justification parameters of digital images. The selection of points, techniques of forming digital models, role of approximate values, structure of image and existing conditions have been discussed, and then the three methods of transfer of points in aerial triangulation have been compared.
Rashid Ahmadi (Translator)
Volume 5, Issue 20 , February 1996, Pages 51-56
Abstract
Mass movements are all the movements that occur on mountain sides because of the gravity of earth. These movements are divided into different types such as falls, slides, creeps, solifluction, flows, etc.
In some areas these movements and their consequent erosion play greater role in sedimentation and ...
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Mass movements are all the movements that occur on mountain sides because of the gravity of earth. These movements are divided into different types such as falls, slides, creeps, solifluction, flows, etc.
In some areas these movements and their consequent erosion play greater role in sedimentation and changes in shape of slopes than other types of erosion. Although human casualties caused by such movements are not vast, but these movements inflict colossal damages on the country’s lands and infrastructures every year. For example, these movements bring about one billion dollars of damage to national lands and infrastructure in the United States every year. In our country, the share of mass movements in annual damages have been estimated as about five hundred billion rials (Ministry of Interior’s National Committee on Natural Disaster Reduction,1994).
On the other hand, identification and study of these movements requires equipment and implementation of certain methods. One of the best and simplest tools for such aims is aerial photography.
Ramin Kiamehr
Volume 5, Issue 20 , February 1996, Pages 57-61
Abstract
In recent decade, great progress has been made in diversification and completion of surveying software, and utilization of these software programs has become common as a major tool. The aim of this paper is to review the gamut of available software programs in the field of surveying that can be run on ...
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In recent decade, great progress has been made in diversification and completion of surveying software, and utilization of these software programs has become common as a major tool. The aim of this paper is to review the gamut of available software programs in the field of surveying that can be run on personal computers, determine major parameters such as necessary computer hardware and operating system, and compare the cost of the minimum and maximum of structure required for implementation of such software. In short, this paper can act as a suitable guide for surveying organizations in selection of new software programs.
Daniel Krinsli
Volume 5, Issue 20 , February 1996, Pages 62-64
Abstract
These playas cover from 25 to 528225 square kilometers (Dasht-e Kavir). Thirty-three playas have areas less than 300 square kilometers, and except Dasht-e Kavir, the largest playa is 4685 square kilometers wide.
Twenty playas were studied directly on the ground, twenty by low-height airplane flights ...
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These playas cover from 25 to 528225 square kilometers (Dasht-e Kavir). Thirty-three playas have areas less than 300 square kilometers, and except Dasht-e Kavir, the largest playa is 4685 square kilometers wide.
Twenty playas were studied directly on the ground, twenty by low-height airplane flights and twenty by aerial photographs. The goal of these studies was to prepare maps and identify hydrological and lithological conditions and their genesis.
Iran’s playas have been usually formed on low lands, and a number of them are located amongst mountains. Climate, vegetation, lithology, structure, terrain and water catchment and drainage systems are the main creators of the environment and shape of playas.
