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Fuzzy Point Averaging of the GPS Position Components
 Figure 1. Dilution of Precision: (a) Poor DOP, (b) Good DOP Another term is TDOP, or Time Dilution of Precision. TDOP refers to satellite clock offset. The relationship between PDOP, TDOP, and GDOP can be expressed as [1,2]: GDOP= Ö(PDOP2+TDOP2) (1) Also, the relationship between HDOP, VDOP, and PDOP can be expressed as [1,2]: PDOP= Ö(HDOP2+VDOP2) (2) IV. Fuzzy Processings A. Fuzzy System1 with PDOP The block diagram of proposed fuzzy system is shown in figure 2. The PDOP and the Sum of Signal to Noise Ratio (SNRs) are used as input fuzzy variables to this fuzzy system. Fuzzy system output is defined as Reliable Factor (R.F.). PDOP and SNRs are divided into three and four segments for partition the rule space, respectively. R.F. is fuzzied with a singleton membership function. The membership functions are defined as figure 3, where S, M, B, MS and MB express Small, Medium, Big, Medium Small and Medium Big, respectively. Twelve rules in the rule base are defined as table 1.  Figure 2. The block diagram of proposed fuzzy system1  Figure 3. Membership functions: (a) PDOP, (b) SNRs and (c) R.F. Table 1. Twelve rules in the rule base of fuzzy system1 
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