The National Geodetic Survey (NGS) will replace all three North American Datum of 1983 (NAD 83) frames and all vertical datums, including the North American Vertical Datum of 1988 (NAVD 88), with four new terrestrial reference frames and a geopotential datum. The new reference frames will rely primarily on Global Navigation Satellite Systems (GNSS), such as the Global Positioning System (GPS), as well as on a gravimetric geoid model. NGS has prepared three documents that outline the technical and policy decisions about replacing NAD 83 and NAVD 88: (1) Part 1: Geometric Coordinates publication outlines technical and policy decisions about replacing NAD 83, (2) Part 2: Geopotential Coordinates publication discusses the planned replacement of all vertical datums of the NSRS, and (3) Part 3: Working in the Modernized NSRS publication addresses how geospatial professionals can expect to work within the newly-modernized NSRS when NAD 83 and NAVD 88 are replaced.
This course addresses technical and policy decisions based on NOAA Technical Report NOS NGS Blueprint for the Modernized NSRS, Part 3: Working in the Modernized NSRS, Revised February 2021. The course will provide a review of the types of heights involved in computing GNSS-derived orthometric heights; explain why you need to understand how to compute GNSS-derived heights to perform leveling in the new, modernized NSRS; describe how leveling data will be incorporated into the new North American-Pacific Geopotential Datum of 2022; illustrate the new procedures that will have to be followed in the new NSRS to process leveling data using NGS software, and describe how NGS will accept leveling data in the new NSRS.
Learning Objectives
- Develop an understanding of the different types of heights and their relationship that are involved in computing GNSS-derived orthometric heights,
- Use NGS’s xGEOIDs to provide a preliminary view of the changes expected from the upcoming North American-Pacific Geopotential Datum of 2022 (NAPGD2022),
- Understand how hybrid geoid models relate to geoid models and conversion surfaces,
- Learn the new procedures for performing leveling projects that will be incorporated into the new modernized 2022 NSRS,
- The geometric terrestrial frame will have a time-dependent component and so will the geopotential datum. Learn how to determine the dates of a Geometric Adjustment Window based on the policy in February 2021.
