Localizer performance with vertical guidance (LPV) are the highest precision GPS aviation instrument approach procedures currently available without specialized aircrew training requirements, such as required navigation performance (RNP). Landing minima are usually similar to those of a Cat I instrument landing system (ILS), that is, a decision height of 200 feet (61 m) and visibility of 800 m. Lateral guidance (LNAV) using WAAS and GPS is equivalent to a localizer, and uses a ground-independent electronic glide path. Altitude calculation using WAAS at approved sites are equivalent to a VNAV. Thus the combination is similar to LNAV/VNAV and decision altitude (DA) can be as low as 200 feet. In the beginning LPV were commonly LPV-250, which had a 250-feet DA. LPV-200 with 200-feet DA entered into use in the late 2010s and early 2020s.