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Articles in the Geodesy Category

Geodesy

Mar 2013 | No Comment

Geospatial Information Authority of Japan (GSI) is the governing institute on geodetic survey and mapping. It manages about 130,000 geodetic reference points in Japan and their survey results are consistent with the International Terrestrial Reference Frame. The recent development of GNSS technology led to more than 1,200 GNSS-based control stations with operation system called GEONET as new geodetic reference points.

Geodesy

Jan 2013 | No Comment

Polar motion refers to the earth rotation axis and surface intersection point’s slow moving on the earth surface [1], realtime acquisition of polar motion is of great signifi cance to high precision satellite navigation, satellite laser ranging and deep space exploration. At present, the international high accuracy polar motion value is obtained through VLBI and SLR technology observation data calculation…

Geodesy

Dec 2012 | No Comment

WGS84 is a widely used reference system for navigation purposes, especially using GNSS technologies (Hoffman-Wellenchoff et al. 1997). Furthermore, navigation tools like Google Earth, uses WGS84 coordinates for point acquisition.

Geodesy

Aug 2012 | No Comment

The geoid can be determined using different method such as gravimetric, astro-geodetic, GPS/ Levelling and “satlevel”. ‘Satlevel’ is a new method of geoid determination, in which the ellipsoidal height is used with orthometric height to model the geoid. Geoid modelling is a process of developing mathematical algorithms to represent the geoid. This is the reference surface for orthometric height. Geoid is one of the geodetic surfaces.

Geodesy

Jun 2012 | No Comment

We have read this article with interest and appreciate the opportunity offered to us by the Coordinates’ Editor to debate the point of view presented there regarding the evolution of Geodesy in different parts of the world. We hope the arguments presented in the following paragraphs provide valuable information regarding the current situation of Geodesy in the Latin America and Caribbean regions.

Geodesy

Apr 2012 | One Comment

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.

Geodesy

Mar 2012 | No Comment

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.

Geodesy

Feb 2012 | No Comment

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.

Geodesy

Nov 2011 | One Comment

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.

Geodesy

Nov 2011 | No Comment

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