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: GNSS
Satellite positioning and its uses in surveying, navigation, and observing a changing Earth.
Measuring the World
The New NSRS Is Coming: A Field-to-Office Guide for Surveyors
An entry-level, field-to-office guide to NATRF2022, NAPGD2022, SPCS2022, epochs, height modernization, and preparing survey workflows for the modernized National Spatial Reference System.
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.
Engineering & Infrastructure
Surveying the Panama Canal, Part 3: Measuring a Living Canal
How hydrography, deformation monitoring, as-builts, and modern geospatial control support an operating and expanding canal.
Measuring the World
Surveying the Highest Peak, Part 3: GPS, Geoids, Snow, and the Modern Height of Everest
Why modern Everest measurements depend on GNSS, gravity, snow depth, reference frames, and a clear definition of height.