The table at left summarizes the accuracies using different ionosphere corrections. Now that SA has been removed, the impact of ionospheric error on positional scatter is clearly evident. As seen in the figures, ionospheric effects cause the long streams extending from the center of the distributions. The best ionospheric corrections are typically, although not always, obtained through the dual frequency correction. The dual frequency results produce a more evenly clustered distribution of data.
Patterns are clearly evident in the table.
Dual frequency results tend to provide a uniform level of accuracy. The single frequency, no-model results show the greatest variations. Of particular interest is the large, no-model increase on and after May 14. The single frequency, broadcast ion model scatters tend to fall between the other results. In the interest of completeness, it should be pointed out that dual frequency ionosphere correction represents a measurement of the ionosphere, and is subject to the multipath error on both the L1 and on the L2 pseudoranges.