Robots to improve satellite positioning accuracy in Australia
Robots to improve satellite positioning accuracy in Australia
Robots to improve satellite positioning accuracy in Australia
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AUSGEO NEWS ISSUE 110 Jun 2013<strong>in</strong> communications, ground <strong>in</strong>frastructure and the expense of thereceivers have meant that this capability has not transferred <strong>to</strong> themass-consumer market. But this is set <strong>to</strong> change as the national GNSSnetwork is supplemented with more sites with better communicationl<strong>in</strong>ks, high quality user receivers become cheaper and analysistechniques become more sophisticated.Figure 1: An ideal antenna, no bias (modifed from Gerry Mader).Figure 2: A typical antenna, with bias (modifed from Gerry Mader).Modell<strong>in</strong>g antennabiasesIn the attempt <strong>to</strong> further <strong>improve</strong><strong>position<strong>in</strong>g</strong> <strong>accuracy</strong>, the geodeticcommunity have looked <strong>to</strong> eachand every error source and haveattempted <strong>to</strong> either elim<strong>in</strong>ate orbetter model that error. GNSSantenna biases are one such errorsource. All GNSS antennas havesmall <strong>in</strong>consistencies <strong>in</strong> theirelectronic components caused bythe manufactur<strong>in</strong>g process thatcurrently limit their <strong>accuracy</strong>(compare Figure 1 and Figure 2).This is where the robots come <strong>in</strong>:they provide a means <strong>to</strong> <strong>in</strong>vestigateand develop models of the antennabiases. Essentially, antenna biasesvary depend<strong>in</strong>g on the position ofeach <strong>satellite</strong> as they move acrossthe skyl<strong>in</strong>e (that is, the <strong>satellite</strong>’sazimuth and elevation). By rotat<strong>in</strong>gand tilt<strong>in</strong>g the GNSS antennawith a robot as it tracks the GNSS<strong>satellite</strong>s, a highly accurate model ofthe antenna bias can be determ<strong>in</strong>ed(Figure 3). By apply<strong>in</strong>g the modelsderived from the robotic system,these biases can be removed and thepositional <strong>accuracy</strong> <strong>improve</strong>d.The GNSS research communityhave up until recently used genericantenna models for antenna types.However, with the ever grow<strong>in</strong>g<strong>accuracy</strong> requirements of GNSSusers, <strong>in</strong>dividual antenna-specificmodell<strong>in</strong>g is necessary <strong>to</strong> further<strong>improve</strong> <strong>position<strong>in</strong>g</strong> <strong>accuracy</strong>.Antenna-specific models can onlybe derived us<strong>in</strong>g robotic calibrationsystems or prohibitively expensiveanechoic chambers, neither ofwhich was available <strong>to</strong> researchers<strong>in</strong> <strong>Australia</strong>, until now.<strong>Robots</strong> <strong>to</strong> <strong>improve</strong> <strong>satellite</strong> <strong>position<strong>in</strong>g</strong> <strong>accuracy</strong> <strong>in</strong> <strong>Australia</strong> www.ga.gov.au/ausgeonews/ | 2
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