The ionosphere is one of the main error sources for single-frequency Global Navigation Satellite System (GNSS) measurements in open-sky scenario. Most widespread GNSS devices are single frequency stand-alone receivers and they can use different Ionospheric Correction Algorithms (ICA) in order to reduce the ionospheric error. In this work two ICA models are considered, specifically Klobuchar and NeQuick-G models. These algorithms are driven by parameters broadcast within GPS and Galileo navigation messages respectively. Hence no additional infrastructure is needed to reduce the ionospheric effects. The main goal of the paper is to analyze the performance of a modified approach for NeQuick-G (defined NeQuick VP) by comparing its performance, in position domain, with respect to the standard NeQuick-G algorithm and to Klobuchar one. NeQuick VP is a methodology proposed to reduce the complexity characterizing NeQuick-G model. The performance is evaluated using real data collected by an open-sky station; the results obtained are analyzed using Root Mean Square (RMS), mean and maximum errors as Key Performance Indicators (KPIs) for both horizontal and vertical components.