Partial measurements in Orekit


I wanted to know if Orekit can be used with partial measurement. For example, I have AzEl measurements, but my Azimuths are wrong, so I want to work only with my Elevations. Is there a way to use Orekit AngularAzEl? Do I have to create a new, specific AbstractMeasurement?

Thank you,


Hi @valerian,

I think you will be better off creating a new class derived from AbstractMeasurement, it will be cleaner.
Or you can create a new class derived from AngularAzEl that will implement the method theoreticalEvaluation.
Inside you would call super.theoreticalEvaluation(...) and use this to create the elevation-only output.

There may be a trick to avoid this for an orbit determination application.
You could try setting the sigmas of azimuths to infinity or their weights to zero.
That way the residuals and partial derivatives of azimuth would always be 0.
But you will end up with a Jacobian matrix with lines of zeros and I don’t think the matrix inversion would end up well with this…

Note that you cannot use an OutlierFilter to reject the azimuth part of your measurements since the filter will disable the whole measurement (azimuth AND elevation) and not just one component.

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Thank you for your answer, I think your first answer is a good solution to my problem!