Center for Mapping

Data Processing Technique

 

The data collected during all three experiments were processed with Trimble GPSurvey software, in a double difference mode with ambiguities fixed to their integer values, fixed (known) antenna positions, and a 10-degree elevation mask. Under the simplified assumption that atmospheric errors cancel out for zero baselines, and are significantly reduced for short (10-meter) baselines, the receiver noise (and possibly multipath) becomes the primary component of the measurement residuals. Since the prime interest of this analysis is the comparison of the level of measurement noise (residuals) provided by different hardware, as well as the ability to maintain lock to the satellites under less than ideal field conditions, the single difference L1 residual plots and the observability charts provided by the GPSurvey software are presented and analyzed (L2 residual plots are not provided by the software).  Naturally, the most desirable measure of the receiver noise characteristics (if other sources of noise could be discarded) would be a one-way residual. However, the GPSurvey software does not provide this measure. Under a simplified assumption that receivers of the same type have identical noise level, the one-way residuals could be estimated at the level of one half of their single difference counterparts.