what is the difference between LPV and LNAV/VNAV

LPV (Localizer Performance with Vertical guidance) and LNAV/VNAV (Lateral Navigation/Vertical Navigation) are both approaches designed for aircraft navigation but serve different purposes and have different requirements regarding precision and equipment. ### LPV (Localizer Performance with Vertical Guidance) - **Precision**: LPV approaches provide precision similar to that of an ILS (Instrument Landing System) but use GPS signals instead. They utilize the Wide Area Augmentation System (WAAS) to enhance the accuracy of GPS. - **Vertical Guidance**: LPV approaches provide both lateral and vertical guidance, allowing for a glide path to the runway. The vertical guidance allows pilots to follow a defined approach slope down to a decision altitude. - **Decision Altitude**: LPV approaches typically have lower decision altitudes than LNAV/VNAV approaches, which may allow for lower minimums in certain situations. - **Equipment Required**: Aircraft must be equipped with WAAS-capable GPS receivers to execute LPV approaches. ### LNAV/VNAV (Lateral Navigation/Vertical Navigation) - **Precision**: LNAV/VNAV approaches are less precise than LPV approaches. They provide lateral navigation guidance (LNAV) and vertical navigation guidance (VNAV) but are not reliant on WAAS. - **Vertical Guidance**: VNAV provides vertical profiles usually based on altitude constraints rather than a specific glide path. It can be less accurate, and vertical guidance may be provided via barometric information rather than through GPS. - **Decision Altitude**: Generally, the decision altitudes for LNAV/VNAV approaches are higher than those for LPV approaches, reflecting the difference in precision. - **Equipment Required**: Aircraft must have a compatible navigation system, such as a barometric altimeter for VNAV, but do not necessarily need WAAS capability. ### Summary In summary, LPV approaches are more precise and rely on GPS augmented by WAAS to provide both lateral and vertical guidance, enabling lower minimums than LNAV/VNAV approaches, which may provide vertical guidance based on barometric altimetry and are generally less precise. The choice between these approaches often depends on the equipped capabilities of the aircraft and the specific requirements of a given approach procedure.