GPS World, October 2009

Algorithms Methods INNOVATION ANDRIA BILICH is a geodesist with the National Geodetic Surveys Geosciences Research Division in Boulder Colorado Her research interests include GPS multipath characterization antenna calibration and precision improvements to high rate positioning for geoscience applications She received her B S in geophysics in 1999 from the University of Texas and a Ph D in aerospace engineering in 2006 from the University of Colorado Dr Bilich was the recipient of the 2007 Parkinson Award from The Institute of Navigation for her dissertation titled Improving the Precision and Accuracy of Geodetic GPS Applications to Multipath and Seismology KRISTINE M LARSON received a B A in engineering sciences from Harvard University in 1985 and a Ph D in geophysics from the Scripps Institution of Oceanography University of California at San Diego in 1990 Since 1990 she has been a faculty member in the Department of Aerospace Engineering Sciences at the University of Colorado at Boulder The primary focus of her work is developing and improving GPS applications for measuring plate tectonics episodic slip volcanic deformation ice sheet motion timing seismic waves soil moisture and snow depth Manufacturers The Salar de Uyuni and Mauna Kea data sets were obtained from Ashtech now Magellan Professional www promagellangps com Z 12 receivers using Allen Osborne Associates acquired by ITT Communications Systems www cs itt com AOAD M_ T element antennas while the soil moisture experiment data set was from a Trimble www trimble com NetRS receiver fed by a model TRM2965900 choke ring antenna with SCIT radome FURTHER READING Multipath Basics and Mitigation Techniques Introduction to Multipath Why is Multipath Such a Problem for GNSS by A Bilich in GPS Worlds online Tech Talk http techtalk sidt gpsworld com p 14 posted January 19 2008 GPS Receiver Architectures and Measurements by M S Braasch and A J van Dierendonck in Proceedings of the IEEE Vol 87 No 1 January 1999 pp 48 64 Conquering Multipath The GPS Accuracy Battle by L R Weill in GPS World Vol 8 No 4 April 1997 pp 59 66 Multipath Effects by M S Braasch in Global Positioning System Theory and Applications edited by B W Parkinson J J Spilker Jr P Axelrad and P Enge Vol 1 Chp 14 American Institute of Aeronautics and Astronautics Washington D C 1996 Multipath Ray Tracing Development and Testing of a New Ray Tracing Approach to GNSS Carrier Phase Multipath Modelling by L Lau and P A Cross in Journal of Geodesy Vol 81 No 11 pp 713 732 2007 doi 101007 s00190 007 0139 z Assessing and Modeling Multipath Using Signal to Noise Ratios Mapping the GPS Multipath Environment Using the Signal to Noise Ratio SNR by A Bilich and K M Larson in Radio Science Vol 42 RS6003 2007 doi 101029 2007RS003652 Scientific Utility of the Signal to Noise Ratio SNR Reported by Geodetic GPS Receivers by A Bilich P Axelrad and K M Larson in Proceedings of ION GNSS 2007 the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation Fort Worth Texas September 26 28 2007 pp 1999 2010 Modeling GPS Phase Multipath with SNR Case Study from Salar de Uyuni Bolivia by A Bilich K M Larson and P Axelrad in Journal of Geophysical Research Vol 113 B04401 2008 doi 101029 2007JB005194 Using GPS to Estimate Soil Moisture Using GPS Receivers to Measure Soil Moisture Fluctuations Initial Results by K M Larson E E Small E Gutmann A Bilich P Axelrad and J Braun in GPS Solutions Vol 12 No 3 pp 173 177 2008 doi 101007 s10291 007 0076 6 Use of GPS Receivers as a Soil Moisture Network for Water Cycle Studies by K M Larson E E Small E D Gutmann A L Bilich J J Braun and V U Zavorotny in Geophysical Research Letters Vol 35 L24405 2008 doi 101029 2008GL036013 Measuring Reflected GPS Signals from Space Reflecting on GPS Sensing Land and Ice from Low Earth Orbit by S T Gleason in GPS World Vol 18 No 10 October 2007 pp 44 49 A Passive Reflectometry and Interferometry System PARIS Application to Ocean Altimetry by M Martin Neira in ESA Journal Vol 17 No 4 1993 pp 331 355 Th anks to Septentrio GPS technology we can run 24 7 operation with 0 misplaced containers Stephan Gosiau Technical Director PSA HNN A giant container terminal in the port of Antwerp Its hard to imagine a more complex day to day reality than that Around the clock massive freights are shipped unshipped and moved around the terminal What could well be a logistical nightmare now runs smoothly with the aid of Septentrios ultra precise positioning techniques Why Because we are reliable experts Because we are ahead www gpsworld com October 2009 GPS World 39