was better than the GPS linked system. However, we have to prepare special measurement systems equipped with optical cable connection. This also decrease applicability of OTPA. In this study, we then considered a post processing procedure to obtain accurate contribution of each reference point to the response point using several measurement systems without any special additional link system.
Contribution calculation by OTPA using several measurement systems 2.1. OTPA calculation flowIn the original OTPA, the contribution of each reference point to the response point is obtained by multiplying each reference signal with the transfer function. The transfer function in this method is calculated using principal component regression method. The calculation procedure is shown in Fig. 1 (Noumura, 2006).