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NOAA Datums Videos 2014

Differential correction with NA2011 and the newest epoch of NAD83

See our and Datums Basics and GPS Tutorials for the long-awaited results of months of rigorous testing and peer review

Trimble Positions software has replaced Trimble GPS Analyst in ArcGIS 10.1

ALASKA GPS and GIS users - check out Joel Cusick's Datum and Projections presentation Feb 2013

ArcGIS 10.1 - New and Cool improvements see Presentation from Melita Kennedy, ESRI : Projections and Datums Dec 2012

Home Datums Basics Difference: NAD27 and NAD83
Difference: NAD27 and NAD83 PDF Print E-mail

Big shift

NAD27 and NAD83

The same set of northing and easting coordinate values in NAD27 results in a NAD83 location 80 meters offset in X almost twice as much in Y for Northern Nevada.  This amount of shift varies by location.  USGS topographic maps were originally based on NAD27.  NAD83 became the new standard in the mid 2000’s.  Always check the stated datum to be sure maps and/or coordinates sets you are given have been updated to NAD83.

NADCON moves between NAD27, NAD83(CORS96), or NAD83(HARN)

In the early 2000’s  USGS, BLM and NPS were mandated to move from NAD27 standard to NAD83

While it is ALWAYS advised to check the datam of any data, take particular note of any data over 10 years old including older printed USGS maps whose coordiantes and grids are NAD27.

Note: It is advised that ArcPad users avoid NAD27