What is the approximate difference in elevation between NGVD29 and NAVD88 in the east?

The National Geodetic Vertical Datum of 1929 (NGVD29) and the North American Vertical Datum of 1988 (NAVD88) are both vertical datums used for surveying and mapping in the United States, but differences can exist due to updates and refinements in the vertical measurement techniques and geophysical models used to establish these datums.

In the eastern United States, it has been established that NAVD88 is generally about 1.3 feet higher than NGVD29. This means that if you are comparing the same point in terms of elevation on these two datums, the elevation value would be approximately 1.3 feet greater when referenced to NAVD88 than when referenced to NGVD29.

Thus, the approximate difference in elevation between NGVD29 and NAVD88 in the east is a negative value of -1.3, indicating that elevations recorded under NGVD29 are approximately 1.3 feet lower than those recorded under NAVD88 in that region. Understanding these differences is critical for surveyors, as using the wrong datum could lead to discrepancies in elevation-related measurements and cartographic applications.