Abbas Ali Saleh Abadi (Translator)
Volume 15, Issue 58 , August 2006, , Pages 28-30
Abstract
The technology of hydrographic Side Scan Sonar has been developed by Professor Harold Edgerton and his colleagues in the year 1960. A Side Scan Sonar is a device that has the ability to search the space around it. The Sonar can be compared with a radar, but in a sonar the reflection of sound waves is ...
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The technology of hydrographic Side Scan Sonar has been developed by Professor Harold Edgerton and his colleagues in the year 1960. A Side Scan Sonar is a device that has the ability to search the space around it. The Sonar can be compared with a radar, but in a sonar the reflection of sound waves is used, unlike radar which uses electromagnetic pulses. Sound pulses usually range between 100 and 500 kHz. The frequencies higher than this magnitude have lower ranges, although they increase the accuracy and resolution.
Abbas Ali Saleh Abadi (Translator)
Volume 12, Issue 46 , August 2003, , Pages 18-23
Abstract
Geodesy of gravity is a branch of geodesy that is mostly related to geophysics and geology. Identification of geodesy of gravity from geometric geodesy is based on relevant measurements and theoretical discussions on gravity field properties. These qualities were the same as those which led to discovery ...
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Geodesy of gravity is a branch of geodesy that is mostly related to geophysics and geology. Identification of geodesy of gravity from geometric geodesy is based on relevant measurements and theoretical discussions on gravity field properties. These qualities were the same as those which led to discovery of the shape of the Earth, when this information made it possible to understand the dimensions and shape of the Earth by measuring the length of the arc of the Meridian. By collecting enough data from the Earth's gravity field, it is possible to determine the geoid separation from the comparison elliptic (Earth's mathematical form) and to determine the density of the Earth. It is also possible to identify changes in the field of gravity in different parts of the Earth. In the year 1738, Pierre Bouguer attempted to measure the relative perpendicular deviation angle by the Earth's radius mapping operation during explorations in Peru in South America.
Abbas Ali Saleh Abadi (Translator)
Volume 12, Issue 48 , February 2003, , Pages 25-27
Abstract
The tide is a completely complex phenomenon that was fully described in the middle of the nineteenth century. The majority of confirmed popular opinions concern this issue.For example, we often assume that the Earth's rotation around itself displaces a great deal of water and creates a tidal wave, or ...
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The tide is a completely complex phenomenon that was fully described in the middle of the nineteenth century. The majority of confirmed popular opinions concern this issue.For example, we often assume that the Earth's rotation around itself displaces a great deal of water and creates a tidal wave, or a decrease in the distance between the Sun and the Earth produces moderate tides. In fact, tide is the result of a system of waves that rapidly spread in the oceans, and produce regular fluctuations of water levels. The order and magnitude of the fluctuation of this phenomenon depend on both astronomical (relative position of the Moon and the Sun) and geographic (coordinates of the studied area) factors.
Abbas Ali Saleh Abadi
Volume 10, Issue 39 , November 2001, , Pages 39-43
Abstract
While everyone can witness and perceive that surface of the earth has an irregular and complicated shape, and it's a clear and definite fact, there are nevertheless many problems in modulating this irregular surface, as well as doing any kind of calculations in connection with it.For our practical applications, ...
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While everyone can witness and perceive that surface of the earth has an irregular and complicated shape, and it's a clear and definite fact, there are nevertheless many problems in modulating this irregular surface, as well as doing any kind of calculations in connection with it.For our practical applications, we need a regular and uniform shape that would be very close to the topographic surface of the earth. Remember that even the topography of the Himalayas Mountains, which are 8 kilometers high, appears as a thin layer in comparison to the 6400-kilometer radius of the earth; in other words, if it is shown in the global topography, it will have a radius of 2 meters, which means that its height cannot exceed 21.2 mm.
Abbas Ali Saleh Abadi (Translator)
Volume 10, Issue 38 , August 2001, , Pages 11-18
Abstract
Although multi-beam echo-sounders have been utilized to transmit and use several types of audio pulses simultaneously in hydrography (to determine the depth and topography of the sea floor) for a long time and are presented at the market for hydrographic equipment, but the extensive use of this type ...
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Although multi-beam echo-sounders have been utilized to transmit and use several types of audio pulses simultaneously in hydrography (to determine the depth and topography of the sea floor) for a long time and are presented at the market for hydrographic equipment, but the extensive use of this type of echo-sounders in marine affairs and military and civilian hydrographic surveying are also very useful.Establishing port facilities and conducting surveying for such civilian applications using old methods (single-beam echo-sounders) requires utilization of a specific and orderly method of hydrography on a series of parallel and pre-designed lines, which is very difficult and time consuming to implement.
The purpose of this discussion is to provide suitable solutions for dealing with hydrographic issues in order to collect precise depth data with better quality and more density. Due to its compact size, echo-sounder can be easily fitted on small marine vessels, and can be used to fulfil the IHOS-44 standard using the great amount of depth-measurement data it collects. On the other hand, modern hydrographic equipment, in turn, necessitates proper and serious hydrographic methods and quality control of marine maps. The proposed methods renowned today are more closely linked to a series of modern hydrographic software that are easily adapted to modern equipment. The stage of processing, which is guaranteed in these equipment by certain software, is dependent on the ability and speed of the computer used for processing throughout its practice: from the stage of collecting raw depth data to application of tidal values, necessary corrections for the device and related errors, and also the stage of mapping and related calculations.
Abbasali Salehabadi (Translator)
Volume 6, Issue 23 , November 1997, , Pages 62-64
Abstract
Before emergence of GPS, the science of navigation couldn’t offer high accuracy in positioning during the day. But, at least it is comforting to remember that the Sun, stars and other celestial bodies are not controlled by super powers. Here, the author describes a system which always receives ...
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Before emergence of GPS, the science of navigation couldn’t offer high accuracy in positioning during the day. But, at least it is comforting to remember that the Sun, stars and other celestial bodies are not controlled by super powers. Here, the author describes a system which always receives its directions from Pentagon and military forces of the United States, and it is possible thanks to the great number of celestial bodies.
Abbasali Salehabadi
Volume 6, Issue 21 , May 1997, , Pages 45-50
Abstract
New methods of tunnel construction and its applications, especially in management and control, usually call for sufficient attention to tunnel’s directing process. New surveying equipment and technologies such as GPS and its long-standing rival, Gyro-theodolite, are able to fulfil this need. On ...
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New methods of tunnel construction and its applications, especially in management and control, usually call for sufficient attention to tunnel’s directing process. New surveying equipment and technologies such as GPS and its long-standing rival, Gyro-theodolite, are able to fulfil this need. On the whole, increase in precision of measurements indicates the necessity of special attention to difficulties of underground surveying.
Abbasali Salehabadi (Translator)
Volume 5, Issue 19 , November 1996, , Pages 30-35
Abstract
By introducing GPS into the global arena and increase in its applications, the basic concepts of geodetic science and surveying have changed. GPS is capable of a relatively fast and accurate determination of position in any weather conditions. Working with it is economical and cost-effective. On the ...
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By introducing GPS into the global arena and increase in its applications, the basic concepts of geodetic science and surveying have changed. GPS is capable of a relatively fast and accurate determination of position in any weather conditions. Working with it is economical and cost-effective. On the other hand, the difference in coordinates taken from GPS is often more important than the equivalent coordinates extracted from drawn or digital maps. The map data contains the long-standing problems arising from determination of planimetric base-level, the image system, surveying operations and their common errors. But these are now better characterized by the coordinates derived from GPS. The GPS is relatively inexpensive, efficient and flexible and determines the three-dimensional position of points with high precision. This technique can be used effectively in navigation, surveying and geodesy. However, there are still some very important issues in combining GPS coordinates with positional information from other methods that are troublesome for us. These issues will become more apparent when the above-mentioned position information is extracted from a digital map database. In general, such information is derived from digitization of linear maps. Therefore, of such positions with the position of the GPS involves in a series of the resulting positions are affected by a variety of errors in the process. Any combination specified computational steps. These computational steps’ purpose is to determine the proper estimation and verification of data between two sets of position presented.
Abbasali Salehabadi (Translator)
Volume 5, Issue 18 , August 1996, , Pages 41-42
Abstract
There is no need to take important and risky measures to obtain highly accurate geographic data using the GPS. Entry into this new technology requires careful observation during the examinations of the costs, and correction of errors. The main motive behind the development of the GPS (Global Positioning ...
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There is no need to take important and risky measures to obtain highly accurate geographic data using the GPS. Entry into this new technology requires careful observation during the examinations of the costs, and correction of errors. The main motive behind the development of the GPS (Global Positioning System) is the need for highly precise navigational tools, which in fact determine the location, speed and time with very high precision. The U.S. Ministry of Defense plays a major role in the development of the GPS system. The main motive behind the development of this system is the urgent need for equipment that can easily assist the deployment of military and war machine and determine the position of individuals, planes and long-range missiles during training and military operations. This system has caused a transformation in the science of positioning. The GPS technology easily determines extremely tiny points at very high precision regardless of weather conditions, during the day or the night. It is also used to collect and access a wide range of geographic data.
Abbasali Salehabadi (Translator)
Volume 5, Issue 17 , May 1996, , Pages 6-10
Abstract
Automatic or semi-automatic short-range digital photogrammetric systems are among the most accurate and efficient instruments for most measurements in industrial production. This paper examines and illustrates the experiences and results of strategic studies on a short-range digital photogrammetric project ...
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Automatic or semi-automatic short-range digital photogrammetric systems are among the most accurate and efficient instruments for most measurements in industrial production. This paper examines and illustrates the experiences and results of strategic studies on a short-range digital photogrammetric project concerning the process of production. These results are related to the application of this technique in the production and quality control carried out in a North American shipyard.
The present article is the result of one of the five strategic research studies conducted by the ETH Institute of Geodesy and Photogrammetry of Zurich, at a shipyard workshop called (BIW) in Mainc, USA.
The purpose of these studies is, in fact, an accurate assessment of the implementation of modern digital photogrammetric systems in the measurement of events occurring during the production stages and their quality control in a shipyard workshop.
The project presented here is the dimensional control of various parts of the body of a ship before it is installed and finalized. In the BIW workshop, the various parts of a body with a nominal dimension of 12 x 25 x 25 meters and weighing several hundred tons are placed on each other and then they are individually prepared and then assembled, and eventually set in a part of the full body of the ship, which is placed in the shipyard.
This method of installing and fitting parts in the construction of ships usually results in an increase in financial costs due to freedom of action.
Abbasali Salehabadi (Translator)
Volume 5, Issue 17 , May 1996, , Pages 17-22
Abstract
Russia's satellite navigation system, known as Glonass, will be completed in late 1995. This system consists of 24 satellites, which move in three elliptical orbits, at a distance of 19,100 kilometers from the Earth’s surface. These satellites introduce the Glonass system, which is subject to comparisons ...
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Russia's satellite navigation system, known as Glonass, will be completed in late 1995. This system consists of 24 satellites, which move in three elliptical orbits, at a distance of 19,100 kilometers from the Earth’s surface. These satellites introduce the Glonass system, which is subject to comparisons with its American counterpart. The question here is that what advantages there are in using either of these systems with a receiver. Currently, both of the navigation systems that are in operation are being investigated. The American system called GPS and Glonass each include 24 satellites. Although there are many similarities between the two systems, their characteristics are completely different, so that they are not effective in running the system.
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.
Abbasali Salehabadi (Translation)
Volume 4, Issue 15 , November 1995, , Pages 7-9
Abstract
On May 10, 1994, the occurrence of a partial or ring eclipse of the sun in North America for more than six minutes fascinated millions of people in these areas. Unlike a general eclipse, a ring eclipse occurs when the moon is at the place on its orbit around the Earth farthest from that planet. In this ...
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On May 10, 1994, the occurrence of a partial or ring eclipse of the sun in North America for more than six minutes fascinated millions of people in these areas. Unlike a general eclipse, a ring eclipse occurs when the moon is at the place on its orbit around the Earth farthest from that planet. In this situation, the diameter of the moon appears slightly smaller than the Sun’s diameter. Thus, the fully-dark image of the moon is visible in the very thin halo of the Sun from above a place in the shadow of the Moon. Observers look at this rare event through special solar filters to see how the Moon's image is embedded in the shining view of the Sun. The occurrence of this phenomenon can be thought of as creating a white hot cavity in the heart of the blue sky. The dark space behind the hot solar ring makes the imagination more powerful. This phenomenon is among the second ring eclipse that has been visible in North America over the last two half-years. But unlike the January 1992 event, which was only visible from southern California, the arctic route on May 10th was eastward along the northwest of Mexico, and so covered most of the United States and the easternmost part of Canada, and was visible in these areas. This event ended at the sunset in the Morocco region.
Abbasali Salehabadi (Translation)
Volume 4, Issue 14 , August 1995, , Pages 53-64
Abstract
In this paper, the observational data provided by two types of GPS operations conducted in July 1991 in the areas of Pohjanmaa and Savo-Kainuu in the country of Finland have been investigated. In this test, the Bernese software system was used to process the data. Although some of the GPS data mentioned ...
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In this paper, the observational data provided by two types of GPS operations conducted in July 1991 in the areas of Pohjanmaa and Savo-Kainuu in the country of Finland have been investigated. In this test, the Bernese software system was used to process the data. Although some of the GPS data mentioned above have been affected by rapid changes in the ionospheric refraction, when particular care is taken with regard to data processing, the concurrent solutions of GPS observational sessions seem to be still useful. On the other hand, the orbital path of each satellite is divided into two circuits, one four-day circuit and the other a three-day circuit. All the satellite orbital paths are corrected and improved in the final mathematical solution by estimating all possible parameters. The magnitude of changes at particular intervals for occupied open- lengths can be achieved by comparing the lengths obtained by the GPS-method with open-lengths derived from classical first-order triangulation.
The results from the Savo-Kainuu region are well matched with the results of combining triangulation networks and even with classical first-order triangulation network. Finally, the results obtained from the Pohjanmaa area are very weak and do not match the results of geodetic (classical) observations.
Abbasali Salehabadi (Translation)
Volume 4, Issue 13 , May 1995, , Pages 12-14
Abstract
The dual elevation system has been used in distribution of the North American Datum (NAD-83), with few people around the world aware of this, if they have previously heard about it at all. The application of this topic here is in fact as a kind of reminder, because there are many geodetic issues that ...
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The dual elevation system has been used in distribution of the North American Datum (NAD-83), with few people around the world aware of this, if they have previously heard about it at all. The application of this topic here is in fact as a kind of reminder, because there are many geodetic issues that are easier to access than this issue. This paper tries to state what this matter is, and why we do need to use it.
Note: "The Canadian part of the Datum (NAD-83), which in some cases has been considered as different from the rest of the Datum parts, is not part of this discussion."
Abbasali Salehabadi (Translation)
Volume 4, Issue 13 , May 1995, , Pages 15-20
Abstract
This paper describes the activities undertaken by HANSA LUFTBILD Corporation over the past two years to employ a GPS system for surveying activities in the fields of air navigation and triangulation. Along with familiarity with the various components of this system, our basic emphasis is on making the ...
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This paper describes the activities undertaken by HANSA LUFTBILD Corporation over the past two years to employ a GPS system for surveying activities in the fields of air navigation and triangulation. Along with familiarity with the various components of this system, our basic emphasis is on making the readers acquainted with the practical results of GPS-based air navigation. The other part of this paper reviews the use of kinematic GPS approach, considering advantages and disadvantages of employing this technique in aerial surveying.
Abbasali Salehabadi (Translator)
Volume 4, Issue 16 , February 1995, , Pages 33-42
Abstract
A radar altimeter installed on the front of a satellite sends electronic pulses to the Earth, and then receives reflections from the ground surface that pass around the satellite. The propagation speed of these waves in space is equal to the speed of light. The satellite radar measures the elapsed time ...
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A radar altimeter installed on the front of a satellite sends electronic pulses to the Earth, and then receives reflections from the ground surface that pass around the satellite. The propagation speed of these waves in space is equal to the speed of light. The satellite radar measures the elapsed time between sending a pulse and receiving its reflection. This time is equivalent to the time it takes for a pulse to cover the distance between the satellite and the earth twice. Therefore, satellite distance from the ground can be measured with great accuracy through measured time. Free electrons (free ions) in the ionospheric layer and suspended particles of water vapor contained in the troposphere layer of the earth reduce the velocity of propagation of waves when passing through these two layers.
Therefore, this slowdown must always be considered in order to prevent large errors in calculating the satellite's height from the ground. After correcting these errors and considering that the position of the radar altimeter system is independently known, the orbit of radar altimeter is determined. Consequently, satellite elevation measurements can be used to achieve accurate topography of the ground. On the other hand, on the oceans the separation of topographic surface from the equipotential surface of the Earth's gravity (geoid) is created by balancing forces generated by the Earth's rotation and ocean currents. Oceanic flows, which contribute greatly to the exchange of heat between the tropical and Polar Regions are ultimately accessible through satellite elevation measurements. Therefore, an altimeter is a unique tool for studying the role of the oceans in the Earth's climate system, as well as in understanding global climate change.
Abbasali Salehabadi (Translation)
Volume 3, Issue 12 , February 1994, , Pages 35-48
Abstract
Two separate types of flights were made in Finland to determine how the position of the aerial camera is determined by the GPS system. The first test flight was conducted for a small block under adverse weather conditions, with the results indicating a high potential for GPS in modifying the block through ...
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Two separate types of flights were made in Finland to determine how the position of the aerial camera is determined by the GPS system. The first test flight was conducted for a small block under adverse weather conditions, with the results indicating a high potential for GPS in modifying the block through the “Bundle Block Adjustment” analytical method. The second flight was a fully functional and justified flight that was performed on an average-level flight block, which, despite the usual issues confronted in this block, the results were very satisfying. Air triangulation carried out by satellite data was very good and satisfactory for preparing maps of 1: 5000 and smaller scale by GPS kinematic method in Finland. On the other hand, the number of control points that can be considered for it is considerably reduced, and this leads us to save money and time compared to the usual classical approach.
