There are two prominent methods to calibrate the antenna channels of a multi-antenna-receiver and estimate the attitude of the antenna array. The Online Calibration calibrates the antenna channels by generating an artificial GNSS signal and feeding that signal into the antenna elements. With the calibration at hand, the attitude is determined by comparing the estimated Direction-of-Arrival (DoA), that can be derived by conventional direction finding algorithms, with the expected DoA, that can be derived by the ephemeris of the satellite. The other method is solely based on the satellite signals and omits the generation of an artificial GNSS signal. Instead it treats the calibration and attitude estimation as a coupled problem. In this paper both method will be evaluated and analyzed using real measurement. In order to put both methods to a stress test, a spoofer signal will be considered in the analysis. To compensate the spoofer effects both methods will be accompanied by an appropriate method to mitigate the spoofer signal. Based on the comparison a novel hybrid method will be proposed which allows to combine the advantages of the aforementioned two methods.