Coordinates : A resource on positioning, navigation and beyond » Geodesy http://mycoordinates.org Mon, 21 May 2012 10:00:18 +0000 en hourly 1 http://wordpress.org/?v=3.1.1 The Missing Observation: Orthometric Height http://mycoordinates.org/the-missing-observation-orthometric-height/ http://mycoordinates.org/the-missing-observation-orthometric-height/#comments Wed, 18 Apr 2012 09:12:26 +0000 admin http://mycoordinates.org/?p=13781 The determination of the coordinates of a point on the earth surface with high accuracy is a real contemporary challenge. Although we are today (2011) equipped with arsenal of unprecedented electronic surveying devices (GPS) receiving positional signals from dozens of satellites orbiting the earth in addition to online public and private geodetic networks broadcasting measurement enhancement, we still didn’t reach the required positional accuracy over our earth globe.]]> http://mycoordinates.org/the-missing-observation-orthometric-height/feed/ 0 The realization of [the] geocentric datum for Brunei Darussalam 2009 http://mycoordinates.org/the-realization-of-the-geocentric-datum-for-brunei-darussalam-2009/ http://mycoordinates.org/the-realization-of-the-geocentric-datum-for-brunei-darussalam-2009/#comments Mon, 12 Mar 2012 16:03:40 +0000 admin http://mycoordinates.org/?p=13325 Replacing the horizontal datum of a country is a complicated and difficult project. The decision to embark on such a “revolutionary” move should only be taken after in-depth studies to identify compelling reasons for such replacement. Here, we comment on the article by Tahir et al. published in the September 2011 issue of Coordinates. ]]> http://mycoordinates.org/the-realization-of-the-geocentric-datum-for-brunei-darussalam-2009/feed/ 0 Choosing the best path: Global to national coordinate transformations http://mycoordinates.org/choosing-the-best-path-global-to-national-coordinate-transformations/ http://mycoordinates.org/choosing-the-best-path-global-to-national-coordinate-transformations/#comments Fri, 17 Feb 2012 11:50:10 +0000 admin http://mycoordinates.org/?p=12965 Obviously, before any datasets can be compared or combined, they must be brought together onto the same datum (Janssen, 2009). The practice of transforming from one datum to another is not diffi cult and the necessary parameters are available in many different software packages. However, with the increased number of datums comes an increased number of ways to transform between datums.]]> http://mycoordinates.org/choosing-the-best-path-global-to-national-coordinate-transformations/feed/ 0 Absolute sea level rise estimation using tide records and GPS observations http://mycoordinates.org/absolute-sea-level-rise-estimation-using-tide-records-and-gps-observations/ http://mycoordinates.org/absolute-sea-level-rise-estimation-using-tide-records-and-gps-observations/#comments Tue, 22 Nov 2011 20:59:23 +0000 admin http://mycoordinates.org/?p=12381 Recent geodetic and oceanographic MSL studies have shown that neither the sea levels nor the land are permanent with respect to time variations. The data analysis of tide gauges produces ‘relative’ sea level changes. However, using tide gauge data alone, it is impossible to distinguish between any true sea level variation and any changes in ground level at a tide gauge site. GPS monitoring can be used to decouple vertical land movements from change in relative MSL, so that tide gauge can provide estimates of changes in absolute MSL. In order to monitor “absolute” changes in sea level, the rates of any vertical land movements at a tide gauge must be determined and subtracted from the resulting rate of tide records [e.g. IPCC, 2001 and Bingley et al, 2000]. Consequently, a sea level monitoring system has been installed at Alexandria tide gauge site containing a GPS receiver as a geodetic monitoring technique to perform this task.]]> http://mycoordinates.org/absolute-sea-level-rise-estimation-using-tide-records-and-gps-observations/feed/ 1 Geodesy: Out with the Old, In with the New http://mycoordinates.org/geodesy-out-with-the-old-in-with-the-new/ http://mycoordinates.org/geodesy-out-with-the-old-in-with-the-new/#comments Tue, 22 Nov 2011 19:03:39 +0000 admin http://mycoordinates.org/?p=12349 Since taking over the position of president of the International Association of Geodesy (IAG – http:// www.iag-aig.org) on the 6th July 2011, I have had on occasion mused on what geodesy “is” and how to explain this arcane field to those who are not acquainted with it. For example, how do I tell the Dean of the Faculty of Engineering, at the University of New South Wales, Sydney (Australia), that I, the head of a department within his faculty which has its primary objective the education of undergraduate students in “surveying” (or more broadly in “geomatics”), now occupy an important position in the geoscience field of “Geodesy and Geophysics”? (This is not an idle exercise, as the Dean will be asked to approve my increased travel commitments over the next four years]]> http://mycoordinates.org/geodesy-out-with-the-old-in-with-the-new/feed/ 0 The realization of geocentric datum for Brunei Darussalam 2009 http://mycoordinates.org/the-realization-of-geocentric-datum-for-brunei-darussalam-2009/ http://mycoordinates.org/the-realization-of-geocentric-datum-for-brunei-darussalam-2009/#comments Sun, 25 Sep 2011 09:31:25 +0000 admin http://mycoordinates.org/?p=12009 The Survey Department of Brunei Darussalam, with the collaboration of the Universiti Teknologi Malaysia (UTM), has carried out a study on the establishment of a new geodetic framework for the country. A new geocentric datum for Brunei Darussalam 2009 (GDBD2009) was established using GPS space geodetic technology based on the ITRF2005 reference frame. The GDBD2009 is related to ITRF2005 through the inclusion of the 8 GPS stations of the Brunei Darussalam Zero Order Network and have been processed together with more than fifty IGS stations around the world. The realization of GDBD2009 requires the determination of a new datum transformation and map projection scheme. A new set of transformation parameters to be use in converting from the existing local datum to the new GDBD2009 has been computed. The implication of this new datum on the existing cadastral and mapping practices, various GPS non-mapping applications, and the GIS/LIS related applications are taken into consideration.]]> http://mycoordinates.org/the-realization-of-geocentric-datum-for-brunei-darussalam-2009/feed/ 0 Implementation of a Semi-Dynamic Datum in New Zealand http://mycoordinates.org/implementation-of-a-semi-dynamic-datum-in-new-zealand-%e2%80%93-ten-years-on/ http://mycoordinates.org/implementation-of-a-semi-dynamic-datum-in-new-zealand-%e2%80%93-ten-years-on/#comments Tue, 21 Jun 2011 13:55:52 +0000 admin http://mycoordinates.org/?p=11438 The use of a semi dynamic datum has been well accepted and its implementation and use have been relatively straight forward from a technical and geodetic perspective.]]> http://mycoordinates.org/implementation-of-a-semi-dynamic-datum-in-new-zealand-%e2%80%93-ten-years-on/feed/ 0 The APREF Project: First Results and Analysis http://mycoordinates.org/the-apref-project-first-results-and-analysis/ http://mycoordinates.org/the-apref-project-first-results-and-analysis/#comments Sat, 21 May 2011 15:03:01 +0000 admin http://mycoordinates.org/?p=11255 Lennard Huisman, John Dawson and Peter J G Teunissen The Asia-Pacific regional geodetic reference frame, presently characterized as a patchwork of national and regional datums, is below the standard that is now available, and expected, in other regions of the world such as Europe (Bruyninx et al, 2001), South America (Luz et al 2002) and North America (Henton et al 2007). ]]> http://mycoordinates.org/the-apref-project-first-results-and-analysis/feed/ 0 Numerical simulations of the optimal geodetic conditions with radioastron http://mycoordinates.org/numerical-simulations-of-the-optimal-geodetic-conditions-with-radioastron/ http://mycoordinates.org/numerical-simulations-of-the-optimal-geodetic-conditions-with-radioastron/#comments Tue, 16 Nov 2010 15:40:11 +0000 admin http://mycoordinates.org/?p=9613 For all the three pillars of space geodesy (the geometry of the Earth surface and its displacements, the orientation of the Earth axis and its rotation speed, and the Earth’s gravity field and its time variations), well-defined, highly accurate and stable global Earth-fixed and celestial reference frames are of primary importance. Over the last decade considerable changes took]]> http://mycoordinates.org/numerical-simulations-of-the-optimal-geodetic-conditions-with-radioastron/feed/ 0 On the estimable parameters for selenodesy with space VLBI http://mycoordinates.org/on-the-estimable-parameters-for-selenodesy-with-space-vlbi-2/ http://mycoordinates.org/on-the-estimable-parameters-for-selenodesy-with-space-vlbi-2/#comments Fri, 16 Apr 2010 21:45:28 +0000 admin http://mycoordinates.org/?p=7263
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Space Very Long Baseline Interferometry (SVLBI) is an extension of the ground-based VLBI technology to space, which involves a simultaneous observation of the same radio source by two stations; one on the ground, the other being space-based. It could not only overcome the baseline length limitation problem specific to groundbased VLBI technology, with a great improvement on the observation resolution, but could also directly... ]]> http://mycoordinates.org/on-the-estimable-parameters-for-selenodesy-with-space-vlbi-2/feed/ 0