Idaho Water Science Center

Boise River Cross Sections

Conducted in cooperation with Federal Emergency Management Agency

Vertical Datum Conversions

Selected Height Conversions for the Study Area

  • near Barber Dam: NAVD 88 - NGVD 29 = 3.20 ft
  • near Capitol Blvd: NAVD 88 - NGVD 29 = 3.06 ft
  • near Glenwood St: NAVD 88 - NGVD 29 = 3.06 ft
  • near Star Road: NAVD 88 - NGVD 29 = 3.04 ft
The conversion program VERTCON computes modeled differences in orthometric height between the North American Vertical Datum of 1988 (NAVD 88) and the National Geodetic Vertical Datum of 1929 (NGVD 29) for a given location specified by latitude and longitude. About 382,000 points throughout the United States were used to compute corrections to the model. The root-mean-squared error was computed to be less than 0.07 ft. The VERTCON program was developed by the National Geodetic Survey (NGS).