Question: how to convert ngvd to navd?
Answer: Conversion between NAVD 88 and the commonly used NGVD 29 varies spatially; however, over most of the study area the following conversion can be used: NGVD 29 = NAVD 88 –3.6 feet. This conversion generally is accurate within about ± 0.5 feet for 95 percent of the study area.