Hi everyone, I have noticed that the GeometryFreeCycleSlipDetector class from orekit does not really apply the geometryFreeCombination of phase signals as described here. Indeed, the transformation of phases from cycles to meters is never done sinceif (obsType1.getMeasurementType() == MeasurementType.CARRIER_PHASE && !Double.isNaN(combinedFrequency)) in the combine function of AbstractDualFrequencyCombination returns false, as the getCombinedFrequency from the GeometryFreeCombination returns a NaN.
I understand the difference in cycles may be similar for ground based applications, but it may cause trouble for space applications where distances vary much more rapidly.
Thanks in advance for you help !
I think using differences directly in cycles is intentional here.
The current implementation results from a discussion in issue 746.
Could you look at this discussion and give us your opinion about this?
I understand that it is more convenient to have a combined measure of the same unit than the initial ones, so one must first comply with the initial definition of the geometry free combination and compute lambda1*L1 - lambda2*L2 to remove the emitter-receiver distance, where L1/2 are assumed to be in cycles as usual in rnx files, then convert it to cycles again with whatever defined combined frequency. The same apply to the iono-free combination, where a frequency does seem to be defined but I have not looked deeper into it.
Also, I see here link that L1/2 where assumed to be in meters since B4 is in meters to (the integer ambiguities has no unit). Maybe the code were written assuming the phase are described in meters ?