RTK fix+float real-time accuracy values

Hi there,

is there a real-time information about RTK accuracy available for an RTK solution based on RTKLIB? I mean something like the plain “old” GPS has where it says it is accurate to maybe 50 or 5 meters depending on signal quality. Is there something similar for RTK? I am testing u-blox NEO M8T with RTKLIB (want to evaluate M8T before buying Reach) and I can see especially the accuracy of FLOAT solution varies wildly - sometime almost as accurate as a FIXed solution, sometimes much less accuate (closer to SINGLE) - in stationary testing I saw float travelling over several meters…

Does a FIXed solution always mean accuracy say in single cm digits (below 10cm level)? I am OK with a degraded accuracy but I need to know how bad it is. My application is on rover so I will deal with partially occluded sky and will probably get FLOAT solution at least partially during my application.

Thanks for your help!


We are going to show precision estimation in one of ReachView next versions. Fixed solution is below 10cm unless due to obstruction you get a false fix, for example due to multipath. Usually in that case it will be detected and receiver will return to float mode to search for correct fix.

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Regarding accuracy - I was advised here to look at N, E, U values in the solution section of the RTKNAVI monitor - I will try.

So there can be a false fix, right? Ehm, this complicates the situation even further… I most likely observed it when a fix in static measurement appeared in multiple locations serveral 10cms apart (probably multiples of wavelength?) from each other during one session. Can a false fix be detected somehow other than by checking whether it “holds” for some time (before the receiver returns to float as you say) - do you have an experience with how fast the receiver can detect it? It would be better for me to be able to detect is from the data itself somehow and not need to rely on the receiver (=RTKLIB) returning to float…

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@kozuch There is a measure of how sure RTKLIB is about a fix, it is called AR ratio. You can view in in real time in RTKNAVI or analyze in logs in RTKPLOT. There is a certain value of AR ratio after RTKLIB will consider solution fixed. You can change it depending on your environment.