Course Description
Geospatial practitioners understand that geodetic leveling procedures are the most accurate means to propagate NAVD 88 orthometric heights. However, the time, effort, resources and specifications to produce publishable 1st or 2nd order vertical heights on bench marks are too onerous a task for most to take on in an economical fashion. Fortunately, NGS Height Modernization techniques allow for users to obtain orthometric heights at usable accuracies for most project work. This session will describe the NGS height modernization program and the important elements of which it is comprised – such as the hybrid geoid model used with GPS derived NAD 83 ellipsoid heights, establishing site control for flood certificate work and the relationship of local mean sea level to our vertical datums. Additionally, the new vertical geopotential datum, to be released around 2022, will be explained.
Learning Objectives
- Heights from the NGS data sheet
- Height modernization intro
- Water levels and establishing site elevations for flood certifications
- Comparing HTMOD to geodetic leveling
- What is a geoidal surface? What is the geoid?
- Hybrid and gravimetric geoids
- The new vertical datum in 2022
- GNSS derived height formula: from GNSS NAD 83 ellipsoid heights to NAVD 88 orthometric heights using the NGS hybrid geoid model
