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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

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

Home GDB Basics Geodatabase Backdoors
Geodatabase Backdoors PDF Print E-mail

Always incorporate backdoors in your GDB.

In the computer world, a 'backdoor' is defined as a method of bypassing normal authentication. Although the implication may have somewhat of a devious tone, that is not the case here.

Suppose you comes across an unexpected object you wish to GPS or you need to enter an attribute value that is not in the drop-down list, or need to enter more than one value from the list. While the advantage of using coded values far outweighs these rare occasions of encountering the unexpected, it does happen and we still need a way to collect the data. No one can plan for and predict the future with 100% accuracy; field-testing and modifications are essential parts of every geodatabase.

Build backdoors into 3 different levels of the geodatabase to ensure that you always have a place to record the unexpected.


For every feature class you create, include an attribute such as Comment to allow for the entry of free-form text to describe the unexpected.

Attributes Values

For all coded values, include attribute values such as Other, Unknown, See Comment etc. This allows you to express the fact that the desired answer is not in the drop-down list or to indicate more than one answer is correct. Use the Comment field to elaborate on your observations.


Include feature classes for a Point_Generic, Line_Generic, and Polygon_Generic to capture the location of the unexpected. Always include a Comment field to elaborate on your observations.

Over time, as the unexpected becomes routine, modify the GDB to include these features and attributes as needed.