Dependence of epoch-wise two-way nested ANOVA estimates of variances of unmodeled effects present in relative GPS positioning on satellite elevation cutoff angle and PDOP mask

Impact of satellite elevation cutoff angle and position dilution of precision (PDOP) mask change on epoch-wise variance components of unmodeled effects that accompany relative Global Positioning System (GPS) positioning is presented herein. Data used for this study refer to the winter and summer periods of the years with minimal (2008) and maximal (2013) solar activity. These data were collected every 30 s in static mode, at two permanent GPS stations located in Montenegro, establishing a medium-distance (116-km-long) baseline with a height difference of approximately 760 m between its endpoints. The study showed that changing satellite elevation cutoff angle, with a fixed PDOP mask, affects epoch-wise two-way nested ANOVA estimates of variances related to the ‘far-field’ multipath (considered as the nested factor herein) and the combined unmodeled effect of tropospheric and ionospheric refraction (considered as the nesting factor herein). However, changing of PDOP mask, with a fixed satellite elevation cutoff angle, doesn't affect epoch-wise two-way nested ANOVA estimate of variance of the combined unmodeled effect of tropospheric and ionospheric refraction, but, generally, affects the estimate of variance of the ‘far-field’ multipath (possibly mixed with a part of a ‘shorter-term’ ionospheric refraction), which is especially pronounced for the summer period. It should also be noted that there is a significant influence of satellite elevation cutoff angle change on both epoch-wise horizontal and vertical position accuracy, only for the summer period, especially in the presence of maximal solar activity, while there is no significant impact of PDOP mask change on epoch-wise positional accuracy.