GPS World, August 2015

Algorithms Methods DESIGN TEST Brazilian oil and gas industry Detailed results of both trials are in the projects final report which can be accessed through the GSA To provide a glimpse of the performance of the CALIBRA algorithms during the offshore trial in FIGURE 1 we selected a period when strong scintillation conditions were encountered In the top plot two height component time series for kinematic PPP processing are shown respectively for the case where no mitigation is applied black time series and the case where the CALIBRA algorithm is applied red time series The bottom plot shows the level of amplitude scintillation S4 index affecting the GPS satellites over a 10o elevation angle The improvement obtained with the CALIBRA solution can be seen in particular during the PPP convergence period 18 00 to 18 30 UT and during the period of strong scintillation 22 30 to 23 30 UT As there was no accurate ground truth available the RMS values with respect to the mean height taken from the quiet period between 19 00 and 22 00 UTC along with the percentage of improvement when applying the CALIBRA mitigation approach are summarized in TABLE 1 Despite all the successful work carried out by CALIBRA the team notes that research must be continued to accomplish further improvement in models and algorithms to finally develop processes for real time operation The challenge would be to counter these ionospheric threats in the scope of an operational service aimed to provide robust highaccuracy positioning to support user applications Furthermore there were strong indications that the addition of Galileo will assist in mitigating the problems addressed in the project when more signals are available in space MARCIO AQUINO is a Principal Research Fellow at the Nottingham Geospatial Institute of Nottingham University and leader of CALIBRA FIGURE 2 TEC map over São Paulo state as forecast by the CALIBRA model on Sept 26 2012 at 2 00 UT The range of the TEC in the image is from 0 to 90 TEC units blue to red The red line is the geomagnetic equator RMS a b Overall Conventional 17158m 14138m 08294m CALIBRA 05613m 05570m 04311m Improvement 67 61 48 TABLE 1 RMS values with respect to mean height 19 00 22 00 UTC www ifen com IRNSS 1 L5 S band with NavX NCS Professional GPS GNSS Simulator In co operation with For additional information contact us www gpsworld com August 2015 GPS World 33