You definitely need a good source of navigational truth data, particularly if you are trying to identify small installation or system errors. For gross navigation accuracy a cross-check with data from a WAAS enabled GPS receiver would be sufficient, particularly if you had a means of logging the doppler and GPS position and along-track velocity data for post-flight comparison. However, for a detailed system performance analysis you would definitely need an INS, or at the very least an IRS, with a real-time display of velocities and/or a data logger, to provide aircraft ground speed data (longitudinal and lateral) for comparison with the doppler system along-heading and cross-heading velocity outputs.
If you are limited to using GPS as your truth data, accurately flying several long, straight route segments would be useful, particularly if you fly it in both directions on a calm day to eliminate any wind-induced errors. If there is a systematic doppler error, you will know because on reaching the end of the segment there will be a position error. The cross-track position error should help you identify if the doppler antenna is not quite aligned with the aircraft longitudinal axis. Any significant systematic along-track error would indicate a problem with the doppler installation as a whole.
For position accuracy it is probably not worth the expense and hassle of using a DGPS system other than WAAS for your navigation truth data, simply because doppler accuracy is not good enough to justify the accuracy of the truth data. However, it may be worth investigating DGPS for as truth data for velocity accuracy, particularly for precision low-velocity doppler applications such as a hover meter. Otherwise an INS would be a good, albeit expensive, source of accurate velocity data.
Hope this helps!
WF
Last edited by WeekendFlyer; 20th October 2010 at 19:54.