Measuring the World
Why Elevation Follows Gravity: The Geoid Beneath Every Height
GNSS measures height above a mathematical ellipsoid, but practical elevation depends on gravity, the geoid, and a physical definition of level.
From the Index
Tag: NAVD 88
Reports, histories, and working notes filed under this subject.
Measuring the World
A History of Datums in America, Part 2: NAD 83, HARN, NAVD 88, and the GPS Era
How NAD 83 evolved through the 1986 adjustment, 83/90-era networks, HARN, FBN, CORS96, NSRS2007, and NAD 83(2011)—and how NAVD 88 replaced NGVD 29.