Abstract
National Adjustment of 2011 and related NGS products and services
Track: Geodesy
Authors: Michael Dennis
As part of continuing efforts to improve the National Spatial Reference System (NSRS), NOAA's National Geodetic Survey (NGS) performed the National Adjustment of 2011 (NA2011). This adjustment yielded updated North American Datum of 1983 (NAD 83) coordinates on more than 80,000 passive control stations positioned using Global Navigation Satellite System (GNSS) technology. It was accomplished through least-squares adjustment of a nationwide network of over 400,000 GNSS vectors. NA2011 was constrained to current NAD 83 coordinates of the NGS Continuously Operating Reference Station (CORS) network, which is a GNSS-based "active" control system and the geometric foundation of the NSRS. Constraining NA2011 to the CORS optimally aligns the GNSS passive control with the active control, providing a unified reference frame. The resulting realization gives positions at a date of January 1, 2010, and it is formally designated as NAD 83(2011) epoch 2010.00.
Completion of NA2011 represents a significant step toward a more integrated NGS, in terms of both better positions and improved access to the NSRS. To illustrated this, NGS products and services related to NA2011 will be covered, including: 1) a new NGS Datasheet format that provides some of the information associated with NA2011; 2) improvements to the NGS "ADJUST" least-squares adjustment program; 3) newly developed GIS tools that convert output from NGS GPS and leveling adjustment software to GIS features; 4) providing NGS products in standard GIS data formats; and 5) new tools to transform positions between the High Accuracy Reference Network (HARN), NSRS2007, and 2011 realizations of NAD 83.