Latest Headlines

NAD 83 Coordinates of CORS Sites Upgraded 04.11.2002

April 11, 2002
/ Print / Reprints /
/ Text Size+
The advancement of GPS technology and methodologies has reached the point that, without much effort, relative positioning of points with respect to the National CORS sites can be accomplished with subcentimeter-level accuracies. Accordingly, the National Geodetic Survey (NGS) has upgraded NAD 83 positions and velocities for all CORS sites, except those located on Pacific Islands, so that they equal the transformed values of recently computed ITRF00 positions and velocities. The applied transformation equations are given at

This upgrade will remove inconsistencies among previously published NAD 83 positions and velocities which are detectable with modern high accuracy GPS surveys. These inconsistencies would have corrupted results obtained with the OPUS (Online Positioning User Service) utility that uses CORS positions and velocities to compute accurate positions for other points.

Moreover, for each CORS site, NGS will now provide NAD 83 positional coordinates that are referenced to an epoch date of 2002.00. That is, the published coordinates for a site's position will correspond to this site's location on January 1, 2002. The site's velocity needs to be applied to compute the site's position on any other date.

Previously, NAD 83 positions for the CORS sites were published for an epoch date of 1997.00 (January 1, 1997). The use of the more current epoch date will reduce those systematic errors occurring when points are positioned relative to CORS sites without applying appropriate site velocities. This more current epoch date will especially benefit those involved in positioning activities in areas of active crustal motion, like western CONUS and Alaska.

Published ITRF00 positional coordinates will continue to be referenced to an epoch date of 1997.00 to remain consistent with international convention.

Did you enjoy this article? Click here to subscribe to POB

You must login or register in order to post a comment.



Image Galleries

HxGN Live

More than 3,500 attendees from more than 70 countries attended HxGN Live, the annual Hexagon AB user conference, at the MGM Grand Hotel & Casino in Las Vegas on June 3-6. About 450 keynotes and panel discussions were held, and several companies from around the world exhibited their geospatial products. Here are a few snapshots from the event.

9/30/14 2:00 pm EDT

Technical Workflows on the Job Site Using 3D Laser Scanning

The purpose of this webinar is to dig into different laser scanning workflows and techniques.


POB September 2014

2014 September

In this September 2014 issue of POB, we take a look at a book that reveals how a rare-map dealer made millions stealing ancient maps. Also, discover the secrets of a 21st-century surveyor and how technology enables small surveying businesses to ease growing pains and maximize their potential.

Table Of Contents Subscribe

Surveying Career

Would you recommend surveying as a career to a current college student?
View Results Poll Archive

Point of Beginning Store

M:\General Shared\__AEC Store Katie Z\AEC Store\Images\POB\epubsite\Statues-pic-large.gif
Surveyor Statues

The perfect gift or award for any special occasion.

More Products

Clear Seas Research

Clear Seas ResearchWith access to over one million professionals and more than 60 industry-specific publications, Clear Seas Research offers relevant insights from those who know your industry best. Let us customize a market research solution that exceeds your marketing goals.

Geo Locator

Buyers Guide

The #1 buyers' guide for land surveyors and geomatics professionals. Search listings for software and equipment manufacturers, equipment dealers and professional services. CLICK HERE to view GeoLocator.


Facebook logo Twitter logo  LinkedIn logo  YouTube logoRPLS small logo

Google +