Robots to improve satellite positioning accuracy in Australia

AUSGEO NEWS ISSUE 110 Jun 2013Australia, and south-east Australia (Gippsland and Otway Basins).Geological evidence suggests that the deformation is likely to besmall, perhaps as little as 0.1 mm/yr, and difficult to measure exceptover very long time spans. However, with improved GNSS antennamodels the possibility of measuring deformation before an earthquakeoccurs may become a reality in time spans of several years. With this,an improved understanding of earthquake hazard in Australia willbe achieved.Figure 4: Robots are used to calibrate GNSS antennas and improve howaccurately we can measure the dynamic Earth.Sensing the atmosphere to improve weatherforecastingThe Earth is surrounded by layers of gases held in place by the Earth’sgravity field. Signals, such as those transmitted by GNSS, propagatedfrom space, are delayed as they pass through the atmosphere. Inthe troposphere, the layer of atmosphere from the Earth’s surface toapproximately 20 kilometres altitude, the delay is proportional totemperature, pressure and humidity. The ionosphere, the layer ofatmosphere from 50–1000 kilometres altitude, causes signal delaysas a function of the frequency of the signal. The composition of boththe troposphere and ionosphere vary both in space and time, and thisvariability currently limits theaccuracy, speed and reliability ofGNSS positioning. But it’s notall bad news, and like a computeraxial tomography (CAT) scanin medical science, the newGNSS signals and satellitescan potentially be combined toprovide a more complete 3Dpicture of the atmospheric delayas a function of time. Modelsthat more completely removethe atmospheric delays will leadto improved accuracy, speed andreliability of positioning, and thisability to sense the atmosphereshould ultimately lead toimproved weather forecastingin Australia.Construction processSite selection and design for theantenna calibration facility beganin the second half of 2011 with anumber of site selection surveysto identify the best location forthe facility on the grounds ofGeoscience Australia. Ultimately,the location on the western sideof the Geoscience Australia’ssupport building was chosenas the preferred site because ofits close connection to a powersupply, good ground conditionsand an unobstructed view tothe north. This is importantfor GNSS users in the southernhemisphere because of GNSSsatellite constellations; themajority of satellites are to thenorth of our location.The construction of thefacility was underway in January2013 with Geoscience Australiamanaging the contractors. TheRobots to improve satellite positioning accuracy in Australia www.ga.gov.au/ausgeonews/ | 4