Abbas Ali Saleh Abadi; Hamid Sadeghi; Hamed Sadeghi
Volume 19, Issue 76 , February 2011, , Pages 45-47
Abstract
One of the important issues in the field of surveying or military affairs is to determine the coordinates of the points on the earth, from which the distances, angles and other parameters of a point compared with the target or any other point can be measured, for which there are many methods including ...
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One of the important issues in the field of surveying or military affairs is to determine the coordinates of the points on the earth, from which the distances, angles and other parameters of a point compared with the target or any other point can be measured, for which there are many methods including photogrammetry and land surveying, especially effective for short distances. But, due to lack of direct vision, these methods are not efficient enough for very long distances, such as thousands of kilometers between the continents. In this case, space and astronomical objects should be used because of the insignificance of the intercontinental distance compared to it, as well as the simultaneous view of the two stations and the space mass in a constant time. The present study describes the method of determining the location using the received waves from anonymous space objects.
Abbas Ali Saleh Abadi
Volume 11, Issue 41 , May 2002, , Pages 41-45
Abstract
Each numerical or geometric quantity, or sets of numerical quantities, which are used as reference or basis for other quantities, are called base levels or datums.In geomorphology, two different baseline levels are considered, one of which is flat, which forms the basis of the accurate calculation in ...
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Each numerical or geometric quantity, or sets of numerical quantities, which are used as reference or basis for other quantities, are called base levels or datums.In geomorphology, two different baseline levels are considered, one of which is flat, which forms the basis of the accurate calculation in horizontal surveying in which the curvature of the earth's surface is considered. The other is the elevation base level according to which the height of points are measured and calculated. In other words, in geodetic surveying the coordinates of different points are obtained from a series of initial points with known coordinates by base line parameters. Due to the development of different methods in surveying, several datums or baselines have been defined and produced.
Today, several datum have been defined and produced for development of geodetic surveying and satellite geodetic methods, and there is no need to have more than one datum in this method. But this does not mean a complete replacement of all datums by a single one, since in practice there are initial surveying parameters and quantities that each depend on the different datums. On the other hand, the overall change of datums will require a century to transform all the information in the maps of a country into a new base level. For example, the issue of determining the sovereignty over the border lines of the US state has been on since centuries ago, and even by drawing up a map of disputed borders, military and civilian users still prefer the old systems of surveying measurement over new ones due to special reasons. Consequently, making general changes in determining the base level not only does not eliminate the problem, but may add another variable to initial problems.
Abbas Ali Saleh Abadi
Volume 10, Issue 37 , May 2001, , Pages 53-58
Abstract
Since ancient times, human being has endeavored to increase its knowledge of the planet on which it lives, though most of its natural phenomena contain complicated mysteries.When humans started farming on land, they began to learn about how the length of day and night are reduced or increased, and also ...
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Since ancient times, human being has endeavored to increase its knowledge of the planet on which it lives, though most of its natural phenomena contain complicated mysteries.When humans started farming on land, they began to learn about how the length of day and night are reduced or increased, and also about the general changes far from the earth's surface which causes the existence of years.
Abbas Ali Saleh Abadi
Volume 10, Issue 40 , February 2001, , Pages 16-20
Abstract
Each numerical or geometric quantity, or sets of numerical quantities, which are used as reference or basis for other quantities, are called base levels or datums. In geomorphology, two different baseline levels are considered, one of which is flat, which forms the basis of the accurate calculation in ...
Read More
Each numerical or geometric quantity, or sets of numerical quantities, which are used as reference or basis for other quantities, are called base levels or datums. In geomorphology, two different baseline levels are considered, one of which is flat, which forms the basis of the accurate calculation in horizontal surveying in which the curvature of the earth's surface is considered. The other is the elevation base level according to which the height of points are measured and calculated. In other words, in geodetic surveying the coordinates of different points are obtained from a series of initial points with known coordinates by base line parameters. Due to the development of different methods in surveying, several datums or baselines have been defined and produced.
Today, several datum have been defined and produced for development of geodetic surveying and satellite geodetic methods, and there is no need to have more than one datum in this method. But this does not mean a complete replacement of all datums by a single one, since in practice there are initial surveying parameters and quantities that each depend on the different datums. On the other hand, the overall change of datums will require a century to transform all the information in the maps of a country into a new base level. For example, the issue of determining the sovereignty over the border lines of the US state has been on since centuries ago, and even by drawing up a map of disputed borders, military and civilian users still prefer the old systems of surveying measurement over new ones due to special reasons. Consequently, making general changes in determining the base level not only does not eliminate the problem, but may add another variable to initial problems.
Abbas Ali Salehabadi
Volume 8, Issue 32 , February 1999, , Pages 51-56
Abstract
When in 1986, GPS satellites were launched into space, nobody could have predicted that this system should overtake traditional and classic methods in surveying activities (such as triangulation and traverse). Since then, almost two generations of GPS receivers have been produced. With advancements in ...
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When in 1986, GPS satellites were launched into space, nobody could have predicted that this system should overtake traditional and classic methods in surveying activities (such as triangulation and traverse). Since then, almost two generations of GPS receivers have been produced. With advancements in human technology and knowledge regarding production of precise computers on smaller scales and with higher speeds of processing, new generations of GPS receivers have become smaller, lighter and of greater power and potential of implementation and storage of satellite measurements in comparison with old receivers. Considering these facts, the new generation of GPS receivers introduced into mark from the year 2000, offer vast hardware and software abilities with wonderful efficiency. These receivers, along with small size and lightness, have high power of initial processing in connection with preparation of positional information. These receivers are able to store information in the main memory up to 16 Mb. They can also receive all the information sent on L1 and L2 carrier frequencies. Therefore, it is possible through utilization of such receivers to achieve the same precision that old receivers obtained by observations as long as about thirty minutes. One of the innovations used in new generation of GPS receivers is a computer chip (IC) that has an astonishing power for removing effective systematic errors that affect GPS measurements, and therefore can provide new GPS receivers with the possibility of precise positioning. This computer chip, known as Paradigm Chip, acts like a small computer “brain” that controls all observational and calculative activities in the receiver.
Abbasali Salehabadi
Volume 7, Issue 26 , August 1998, , Pages 7-13
Abstract
Instantaneous application of distance corrections in the DGPS relative positioning method has led to increase of precision and validity of this method. While great errors such as atmospheric delays and unusual fluctuations in satellite clocks’ behavior and orbital information can affect relative ...
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Instantaneous application of distance corrections in the DGPS relative positioning method has led to increase of precision and validity of this method. While great errors such as atmospheric delays and unusual fluctuations in satellite clocks’ behavior and orbital information can affect relative and movable positioning by GPS, application of DGPS method and its instantaneous corrections brings about precisions of the order of one meter and less for dynamic aims. In this method, instantaneous relative positioning of still receiver with known coordinates is like a pseudo-satellite that can send waves and encoded messages similar to codes sent from satellites to moving receivers. The major advantage of this encoding is prevention of measuring a broad spectrum of waves in a distance from pseudo-satellite in frequency band of GPS wavelengths, namely around 1 to 2 GHz, which propagate in a direct line in atmosphere. Therefore, pseudo-satellite concepts can be used in applications such as aerial surveying and photogrammetry.
Abbasali Salehabadi
Volume 4, Issue 16 , February 1995, , Pages 43-45
Abstract
On March 25, 1989, the US Department of Defense confirmed great fear of the civil users of GPS while S.A is activated. What S.A does is damaging and degrading the precision of GPS signals in order to prevent GPS users from gaining access to this system’s high precision. Experts state that S.A has ...
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On March 25, 1989, the US Department of Defense confirmed great fear of the civil users of GPS while S.A is activated. What S.A does is damaging and degrading the precision of GPS signals in order to prevent GPS users from gaining access to this system’s high precision. Experts state that S.A has less impact on surveying applications than other GPS applications.
When S.A is on, It disrupts satellite data, which occurs through falsifying of satellite clocks and orbital information. Indeed, according to Dr. Javad Ashjaei, head of the “Ashtek and colleagues” Corporation., S.A. will add to the GPS signals’ noises. In fact, signals move forward, backward or around. S.A. falsifies signals to the extent that they report a problem in the orbit of satellites. "S.A only affects the Bloom II satellites, which is conditional on completing the set of GPS satellites."
Abbasali Salehabadi
Volume 3, Issue 11 , November 1994, , Pages 12-19
Abstract
Considering the advancements in GPS technology and applications of this important tool in the world, having a knowledge of the different ways of positioning by this system seems essential. The high precision of this system and its universality are reasons for utilization of this system in all surveying, ...
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Considering the advancements in GPS technology and applications of this important tool in the world, having a knowledge of the different ways of positioning by this system seems essential. The high precision of this system and its universality are reasons for utilization of this system in all surveying, geodetic, hydrographic, imagery (photo) and other works. As an introduction, we will first review the GPS and N.N.S.S positioning systems, and then discuss the mathematical equations and observations of the GPS system in full.
Generally, space-based positioning was begun by NASA since 1960's using the Doppler system. However, it’s time-consuming process and lack of precision caused the US Department of Defense (DOD) in 1974 to declare its need for a comprehensive and global positioning system for its military purposes. This led to the creation of GPS (Global Positioning System), and in 1983, the launch of the first GPS satellite was an effective step in the history of surveying. With the rise of the GPS system all previous systems, including ballistic cameras, Doppler (N.N.S.S.), the LONG-C, OMEGA and SECOR gradually disappeared.
Abbasali Salehabadi
Volume 1, Issue 4 , May 1992, , Pages 44-51
Abstract
There are no doubts in the importance and value of papers describing latest research with newest methods in the surveying world, but it seems to the author that it is also of great importance to present, via a number of articles, reports on innovative works with new tools or new methods conducted in ...
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There are no doubts in the importance and value of papers describing latest research with newest methods in the surveying world, but it seems to the author that it is also of great importance to present, via a number of articles, reports on innovative works with new tools or new methods conducted in the country by Iranian experts and published in the surveying scientific and technical publications of the of the country, though with the possibility that what is said in such articles be old or ordinary compared with international achievements in the field.
The review of prominent world surveying publications, especially multidisciplinary publications that represent the overall gamut of mapping techniques, suggests that part of the papers presented are dedicated to introduction of applied experiments. An expert or a group of mapping experts, after carrying out a routine case of surveying in a particular fashion that they believed had been effective in shortening the time needed to achieve the objectives of the plan or economizing it, exposed the results and experiences through an article to other researchers' view. Although the mathematical aspect of the article might be less significant than specialized geodetic or photogrammetric papers, it is nonetheless of significance as a presentation of a particular experience.
