NGS VERTCON

The NGS VERTCON method is used to compute the difference in orthometric height between the NAVD29 and NAVD88 vertical datums for a specific latitude and longitude (the appropriate orthometric height will be displayed after the conversion). The VERTCON model is accurate to 2 cm (assuming that data collection methods are at least that accurate or better). Since most of the data used to calculate the model falls in the eastern United States, accuracies in that part of the country will tend to be better than elsewhere. 

DATA REQUIREMENTS TO USE THE VERTCON VERTICAL DATUM TRANSFORMATION

• Data points must be within the conterminous 48 United States
• Conversion is ONLY valid for conversions between NGVD29 and NAVD88