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Which vertical datum transformation method is used by the Geographic Calculator and how accurate is it?

April 26, 2017accurate calculator datum geographic method Transformation Used vertical

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Which vertical datum transformation method is used by the Geographic Calculator and how accurate is it?

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The National Geodetic Survey (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. 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.