*3.1. Verification for Cakovec Location ˇ*

The correction values generated by the proposed model are shown in Table 3.


**Table 3.** Values of RTE corrections by the proposed model for Cakovec GNSS location (in m). ˇ

The proposed model generates negative RTE correction values for coordinate axes y and z for 2014 and 2015. For the *x* axis, corrections were made in the range of −0.65 m to 1.69 m (for both years). The absolute amounts of the corrections range from 0.04 m (*y*-axis in 2014) to 2.46 m (*x*-axis in 2015).

The values of the RMSE, the standard deviation (STD), and the associated statistical parameters for the Cakovec GNSS position are shown in Table ˇ 4.

**Table 4.** Comparison of RMSE, STD, range, and median values for the Cakovec GNSS location ˇ obtained using the Saastamoinen model and the proposed model (in m).


Application of the proposed model shows that values of the minimum and maximum deviations do not change significantly with ranges remaining approximately within the usual scale. There was a noticeable tendency for one deviation value to decrease while the opposite value increased and their absolute range values remained the same. Moreover, both minimum and maximum deviation values of the *z* axis decreased in the proposed model for the observed year of 2014.

The 2014 results showed a simultaneous improvement in the accuracy of the position RMSE value, which is the basic parameter for the success of the proposed model. Improvements in accuracy were obtained for the *x*-axis (10.04 cm/2.73%), *y*-axis (0.09 cm/0.04%), and *z*-axis (15.85 cm/3.38%). At the same time, the parameter STD improved for the x- and

*z*-axis, and the value STD decreased for the *y*-axis (−0.03 cm/−0.01%). An improvement of the measurement frequency distribution was also observed. In 2014, the median value obtained with the proposed model for all axes decreased and approached the initial value of the deviation (zero), and in 2015, an improvement of the median value of the x- and z-axes and a deterioration of the *y*-axis was observed. An improvement in position accuracy was seen when comparing the RMSE values over the indicated period. For 2015, the proposed model simultaneously improved the *x*-axis position accuracy (14.26 cm/3.87%) and the *z*-axis accuracy (7.56 cm/1.84%), but it simultaneously worsened the *y*-axis position accuracy (−0.75 cm/−0.32%). It is clear that an overall improvement in position accuracy was achieved when observing the ratio of improvement and the deterioration of the overall position accuracy at the same time.
