Azimuth and Antenna Height Dependencies of Multipath on Global Positioning System (GPS)

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Year:
2015
Type of Publication:
Article
Keywords:
GPS, Antenna, Azimuth, Height, SNR, Multipath
Authors:
Mr. Eshetu Nega Erkihune; Dr. Addisu Hunegnaw
Journal:
IJAIM
Volume:
3
Number:
6
Pages:
281-289
Month:
May
Abstract:
Multipath remains one of the most dominant sources of errors in Global Navigation Satellite Systems (GNSS). It affects both carrier phase and pseudo-range observations. With the use of differential techniques it is possible to remove many of the common error sources, but the error effects of multipath have proven much more intricate and difficult to mitigate. Mainly the GPS Analysis at Massachusetts Institute Technology (GAMIT) software was used to evaluate the assessment of multipath in different azimuth and antenna height at each of the local station. In addition to this, a combination of different scripting programing language and Linux based visualization programs were used to extract multipath estimation on L1 and L2 Global Positioning System (GPS) carrier signals. A comparison of the station azimuth used in local station found at Institute of Geophysics Space Science and Astronomy (IGSA), for this study indicated that 90º and 0º were the most and least affected azimuths respectively. In addition the study highlighted the robustness of Trimble ZypherTM antenna types in combating multipath effects in our station site. Multipath is known to be site dependent. Our Global Positioning System (GPS) observations were made at a site having high vegetation and subsequently the vegetation was removed within 6 meters radius of the measurement point. Our study identified that vegetation is the dominant causes of multipath effects on the study area, in such a way that both the 1.74m and 1.03m heights are affected before the removal of the small bushy vegetation around the measurement point. However, it was worse for the 1.03 meters height than the 1.74m height. Later as the vegetation is removed, 6 meters around the measurement point, multipath effect became less evident. The test made using a different antenna type (LEICA AX1230+ GNSS ) for other two antenna heights 0.980m and 1.685m after the removal of the vegetation reaffirmed the original finding that as antenna height increases multipath effect decreases. This being the general finding, some data results after the removal of vegetation showed an increase in Multipath effect. Close observation showed that during these days the ground was wet and covered by water after heavy rainfall. This is an indication that surface water also because significant multipath effect on Global Positioning System (GPS) signals.
Full text: IJAIM_444_Final.pdf

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