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