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Spirent KB Article
Doc ID: FAQ13942
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Positioning Application: Can I get a Dilution Of Precision (DOP) value of less than 1?
PosApp (SimREPLAY, SimREPLAY+, SimGEN)
Usually the minimum value of DOP is 1 if you are looking at the best 4 satellites.
However this may not necessarily be the case if you are considering all satellites in view.
The nominal error in the calculated position is a function of the relative satellite geometry and the satellite pseudorange errors.
The DOP calculation assumes a one unit error (one metre) in the pseudorange.
So you wouldn't expect the net positional error to be less than this using just four satellites.
If you include a large number of satellites in the DOP calculation then the accuracy of the calculated position will improve correspondingly.
So it is possible the DOP may be reduced to less than 1 in this case.
Situations where this could be true would be:
High elevation vehicles.
Multiple constellations enabled.
Multiple SV's in view.
Shows an example of a GDOP value less than 1 in a scenario with Multiple constellations and High elevation vehicle.
for further details on DOP.
Figure 1 - Example GDOP value less than 1.
Product : SimPLEX,SimREPLAYplus,SimREPLAY,SimGEN,PosApp,DOP,Scenario,Receiver