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Copyright © 2011 SciRes. JGIS

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Figure 3. The approximation error values of GPS GDOP

determined based on RWNN for 900 data with (4, 3, 1)

structure.

Table 3. Comparison CPU time of classical method and NN

approach for GPS GDOP approximation.

Model Name CPU Time [msec.]

Matrix inversion method 1.080

NN approach 0.029

efficiency in comparing with RNN and WNN; this is

because of the RMS approximation error shortage over

them.

Table 3 presents the comparison CPU time of classi-

cal method and NN approach for GPS GDOP approxi-

mation. The simulation results demonstrate that NN ap-

proach is accurate and faster than classical method.

7. Conclusions

In this paper, the rapid and precise calculation of GPS

GDOP using RWNN has been studied for the selection

of an appropriate subset of navigator satellites. The

method of NNs is a realistic computing approach used

for the calculation of GPS GDOP without any need to

inverse matrix, which imposes a huge computing load on

the processor of the navigator. The performance of the

proposed NN has been studied on the test data of the

paper. The results show that the proposed method is fully

capable to select an optimal subset of GPS satellites with

the best geometric configuration. The results of simula-

tion show that the efficiency of RWNN is better than

RNN and WNN.

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