Ongoing Refinement
The previous chapters of this book have built up models for the limited available measurement data and for aircraft motion, and then used these models to produce a pdf of the final aircraft latitude and longitude. In principle, one could use this pdf to d
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Ongoing Refinement
The previous chapters of this book have built up models for the limited available measurement data and for aircraft motion, and then used these models to produce a pdf of the final aircraft latitude and longitude. In principle, one could use this pdf to direct a search and then the very act of searching would provide further measurement data. This chapter describes how the Bayesian method can be used to adapt the position pdf to account for data collected after the accident flight. Two data sources are discussed: the sonar imagery data collected in the search and the discovery of the flaperon on Reunion Island.
11.1 Updating the Distribution Using Search Results The measurements collected as part of the search can be treated in the same mathematical framework as the communications data. This was used, for example, in the search for AF447 [40]. In this case the aircraft is no longer moving so the prediction stage becomes degenerate and the predicted pdf is the same as the previous posterior pdf. The result of the search can be summarised by the probability that the cumulative search effort would have detected the aircraft at any particular location, PD (x). The posterior pdf given the search effort (denoted S) then becomes: p(xfinal |S, Z K ) ∝ [1 − PD (xfinal )] p (xfinal |Z K ) ,
(11.1)
where the constant of proportionality is determined to ensure that the posterior integrates to unity. If a particular area A is searched with a constant probability of detection PD , the probability of finding the aircraft is P(find during search of A) = PD
A
p (xfinal |Z K ) dxfinal .
© Commonwealth of Australia 2016 S. Davey et al., Bayesian Methods in the Search for MH370, SpringerBriefs in Electrical and Computer Engineering, DOI 10.1007/978-981-10-0379-0_11
(11.2)
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11 Ongoing Refinement
In the analysis used for prioritising the search for flight AF447, the probability of detection for areas searched using side-scan sonar was modelled as 0.9 [40]. This type of analysis could be used, for example, to prioritise whether to revisit a more likely area or to search a less likely area that has not yet been searched. Based on the quality assurance process which has been implemented in the MH370 search, which includes revisiting items that have been assessed as potential debris, it is considered highly unlikely that the search would fail to detect the aircraft if the correct location is searched. Due to sensor drop-out and terrain masking, there will inevitably be small pockets which are not covered in a first pass of the search, and (11.1) can be used to determine the priority of returning to ensure that these are examined.
11.2 Reunion Island Debris The apparent lack of debris from the aircraft was a mystery which was resolved in part when a flaperon was discovered washed up on Reunion Island on 29 July 2015, 508 days after the accident, and later confirmed to be from MH370. Two questions arise from this find: 1. What information does the discovery of the flaperon on Reunion Island provide ab
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