Update

GPS-H v3.1 and CGG2010 are now available

Software GPS-H v3.1 and geoid model CGG2010 with its accuracy estimates are now available for download from the CSRS on-line database. GPS-H v3.1 comes with a quick user guide and a help file.

GPS-H v3.1 and CGG2010 are coming soon

NRCan will publish a new version of GPS-H by the end of March 2011.  Version 3.1 represents a complete overall of the user-friendly interface.  It includes a powerful spreadsheet to manipulate data.  It allows more flexibility in terms of input and output formats.  Users can create and saves their own formats.  In addition, version 3.1 allows now input in Cartesian (x, y, and z) and Mercator (easting, northing, height) coordinates.  The Mercator coordinates can be in standard UTM, provincial MTM or in a projection defined by the user.  Geographical coordinates are accepted in decimal degrees (D.D), degrees and decimal minutes (DM.M) and degrees, minutes and decimal seconds (DMS.S).  Finally, version 3.1 can also be run in a batch mode for very large files.  Preview of the new GPS-H is available under the page Tools.

Furthermore, NRCan will publish a new geoid model for Canada: CGG2010.  The model is expected to be available by the end of March 2011.  It will supersede the previous version CGG2005.   CGG2010 will be available in NAD83(CSRS) and ITRF2005 reference frames.  The geoid heights will represent the separation between the GRS80 ellipsoid and the equipotential surface Wo = 62636855.69 m²s^-2.  It is the same reference surface as USGG09 (US NGS) and EGM08 (US NGA) and represents the global mean sea level.  CGG2010 constitutes an improvement over CGG2005 by refining the Stokes integration and by including more accurate data sets.  CGG2010 should be quite representative of the future vertical reference frame for Canada.

NRCan received GOCE data

NRCan received a first dataset from the GOCE mission. The data cover the first cycle (61-day repeat orbit) for the months of November and December 2009. NRCan is presently processing and analyzing the data. Already, we developed a few experimental geoid models which include GOCE data. Preliminary results are being presented at the second symposium of the International Gravity Field Service (IGFS) in Fairbanks, Alaska (20-22 September, 2010).

GOCE mission in operation

The GOCE mission is now in exploitation phase at an altitude slightly below 255 km.  The current orbit is lower than originally planned because there is very little solar activity.  This is good news, as the gravity measurements will be even more accurate. ESA expect to present the first GOCE gravity field in June 2010.  More information about the GOCE mission is available at http://www.esa.int/Our_Activities/Observing_the_Earth/GOCE.

GOCE mission launched

The GOCE mission, launched on March 17, 2009, will determine the static global geoid with an accuracy that could achieve one centimetre at a spatial resolution of 100 km during its planned 24-month lifetime.  GOCE’s highly sensitive gradiometer instrument has been switched on and is producing data.  All systems on the satellite have now been activated.  GOCE was injected into orbit at an altitude of 283 km. Since then, it has been freefalling at a rate of 150 to 200 m a day and will continue to do so until it enters ‘drag-free mode’ at an altitude of 273 km. At this altitude, the satellite will actively compensate for the effect of air drag and its payload will undergo a further six weeks of commissioning and calibration.

New definition of the vertical reference surface

Initially, the selected equipotential surface (WR) was to coincide with the mean water level at the tide gauge in Rimouski, Québec. It would have been the same reference system as NAVD88 and IGLD85. However, US National Geodetic Survey (NGS) intends using the equipotential surface (W0) representing best, in a least-squares sense, the global mean sea level. NRCan is now considering the same definition to assure compatibility along the border. Figure 1 (Rimouski) [JPEG, 655.1 kb, 2700 X 1750, notice] and Figure 2 (MSL) [JPEG, 667.4 kb, 2697 X 1750, notice] depict these two equipotential surfaces with respect to CGVD28.