GPS and Inertial Navigation
June 26, 2009 by airianto
Filed under GNSS, GPS, Geomatics Science
GPS/INS direct georeferencing
GPS aided inertial navigation systems have been available for commercial mapping applications for approximately a decade, pioneered by Canadian-based Applanix Corporation with their POS (Position and Orientation System) technology. The impact on the aerial survey and remote sensing industry has brought about a re-assessment of traditional photogrammetric methodology and the potential elimination of two fundamental mapping components, the ground control survey and corresponding aerotriangulation process.
GPS
GPS Satellite
The Global Positioning System (GPS) is a space-based radio-navigation system consisting of a constellation of satellites and a network of ground stations used for monitoring and control. A minimum of 24 GPS satellites orbit the Earth at an altitude of approximately 11,000 miles providing users with accurate information on position, velocity, and time anywhere in the world and in all weather conditions.
GPS is operated and maintained by the Department of Defense (DoD). The National Space-Based Positioning, Navigation, and Timing (PNT) Executive Committee manages GPS, while the U.S. Coast Guard acts as the civil interface to the public for GPS matters. The Federal Aviation Administration is investigating and applying the use of GPS as it pertains to aviation.
Compass Navigation Satellite
March 16, 2009 by airianto
Filed under COMPASS, GNSS, Geomatics Science
Compass Satellite
The Compass system (also known as Beidou-2, BD2) is a project by China to develop an independent global satellite navigation system. Compass is not an extension to the previously deployed Beidou-1, but a new GNSS system similar in principle to GPS and Galileo.
The new system will be a constellation of 35 satellites, which include 5 geostationary orbit (GEO) satellites and 30 medium Earth orbit (MEO) satellites, that will offer complete coverage of the globe. The ranging signals are based on the CDMA principle and have complex structure typical to Galileo or modernized GPS. Similarly to the other GNSS, there will be two levels of positioning service: open and restricted (military). The public service shall be available globally to general users. When all the currently planned GNSS systems are deployed, the users will benefit from the use of a total constellation of 75+ satellites, which will significantly improve all the aspects of positioning, especially availability of the signals in so-called “urban canyons”. The general designer of Compass navigation system is Sun Jiadong, who is also the general designer of its predecessor, Beidou navigation system.
Low Latitude Troposphere: A Preliminary Study Using GPS CORS Data in South East Asia
January 1, 2009 by airianto
Filed under GPS, Geomatics Science
Hot and wet conditions in the equatorial or low latitude region degrade satellite positioning accuracy noticeably. The degradation is related to the strong tropospheric effect, especially the wet component which is approximately proportional to the content of water vapor in the troposphere and thus makes satellite positioning more challenging in this region.
Despite the efforts to achieve better understanding of the signal delay in the low latitude troposphere, much more still remains to be improved.
Constellation of Galileo Satellites
April 16, 2008 by airianto
Filed under GNSS, Galileo, Geomatics Science
Galileo Constellation
When Galileo, Europe’s own global satellite navigation system, is fully operational, there will be 30 satellites in Medium Earth Orbit (MEO) at an altitude of 23 222 kilometres. Ten satellites will occupy each of three orbital planes inclined at an angle of 56° to the equator. The satellites will be spread evenly around each plane and will take about 14 hours to orbit the Earth. One satellite in each plane will be a spare; on stand-by should any operational satellite fail.
