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). VERTCON implements predetermined grid shifts (analogous to NADCON horizontal grid shift files) for any particular point on the grid. THIS METHOD IS ONLY VALID IN THE CONTERMINOUS UNITED STATES OF AMERICA FOR CONVERSIONS BETWEEN NGVD29 and NAVD88.

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 fall 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
Data points must be on the NAD27 or NAD83 horizontal datum for valid transformations

Note: To use the NGS Vertcon you will need to download the latest Vertical File bundle from our website here.

Vertical Grid Shift Files