Spatial -

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 Reference frame epoch or realization
Reference frame epoch or realization PDF Print E-mail

II. VELOCITY is defined by an EPOCH

An epoch, realization or flavor of a reference system at a specified point in time is a reference frame. While projected coordinate systems flatten the Earth so we can assign location coordinates, plate tectonics keep the continents in constant motion. Therefore coordinates are also tied to a given time. The following is a brief review updates (realizations) of the most common reference systems.