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 GDB Tutorials Step 6: GPS-enable your Geodatabase with Trimble GPS Analyst
Step 6: GPS-enable your Geodatabase with Trimble GPS Analyst PDF Print E-mail

This step not required for ALL geodatabases.

It is REQUIRED for those using ESRI ArcPad to collect data AND processing that data with

Trimble GPS Analyst

1. To enable the GPS Analyst extension

From the ArcCatalog menu bar, select Tools / Extensions

Check the box next to Trimble GPS Analyst


Click Close.

The GPS Analyst extension is now activated

2. To GPS-enable the geodatabase and feature classes

You can GPS-enable a geodatabase at the same time that you create the geodatabase, or later, once it contains GIS features.  For this exercise, we will enable the GDB now before it contains any data.

Right-click on the Training_Day1 geodatabase and choose Properties

Click on the Trimble GPS Analyst tab

Place a checkmark next to the GPS-enable geodatabase box

Place a checkmark next to the feature classes you wish to GPS-enable.

Click the Select All button to GPS-enable all listed feature classes.


Click OK

3. To specify accuracy values for validation

You can specify or change the accuracy required for a feature class at any time. For this exercise, we will specify the required accuracy now, before we check out the data to ArcPad.

4. To specify accuracy values for all feature classes

Return to the Trimble GPS Analyst tab

Click the Feature Class Properties button

In the Store average estimated accuracy box, enter the attribute field name avg_accuracy

In the Store worst estimated accuracy box, enter the attribute field name worst_accuracy

In the Accuracy required for validation box, enter the value 3.000 ft

The completed window should look similar to this –


For this first exercise, 3 feet is an acceptable horizontal accuracy.  This value is based on the specifications of your GPS receiver and the goals of the data you are trying to collect.


This sets the properties of all GPS-enabled feature classes to the same values. To edit the individual feature classes, right-click on that feature class and choose Properties.

Where you entered 3.000 ft for accuracy required for validation, 0.0914 m would have been the mathematically equivalent and a valid entry in the dialog box. The below table display ArcGIS standards for unit abbreviations.

Units                          Abbreviation

Millimeters                  mm

Centimeters                 cm

Meters                             m

Kilometers                   km

Inches                            in

Feet                                 ft

Yard                               yd

Miles                              mi

Nautical miles            nm

Decimal degrees        dd

Radians                        rad

5. To view the required accuracies

Now all the feature classes in the geodatabase have the same accuracy requirements for validation.


Click OK to close the Database Properties window

6. To view the results of your efforts

Note the appearance of the GPS Sessions folder button and its hierarchy within the geodatabase of the resulting feature dataset in ArcCatalog.


7. To view the created accuracy fields in the attribute table

View the properties of any one of the feature classes you have GPS-enabled.

Hint: Right-click on any feature class and choose Properties

Click on the Fields tab

What new fields have appeared and of what data types are they?



In this exercise, we specified a WGS-84 coordinate system for our feature dataset (and subsequently, the feature classes). Therefore, a geographic transformation will not need to be selected for our exercise.

Coordinate systems other than WGS-84

If the feature classes in the geodatabase(s) at your office are not referenced to the WGS-84 coordinate system, a geographic transformation will need to be selected. This specifies which datum transformation GPS Analyst will use to correctly convert GPS data from its stored WGS-84 coordinates to the coordinate system of your GIS.


ArcGIS uses the EPSG codes for datum transformations.

NAD_1983_To_WGS_1984_1    NAD 83 (1986) - "zero" datum shift

NAD_1983_To_WGS_1984_2    Alaska Aleutians

NAD_1983_To_WGS_1984_3    Hawaii

NAD_1983_To_WGS_1984_4    United States - ITRF94

NAD_1983_To_WGS_1984_5    United States - ITRF96


Transform _1 is a null transform where all parameters are held at 0 and data does not move at all.  It is the safest choice to define your data as NAD83 in the ArcGIS environment without shifting your data as collected by GPS.

Transform _5 is an older transform, which moves data from the older ITRF96 datum.  ArcGIS has not yet incorporated the latest parameters to move data from WGS-84 to the most recent ITRF00.  For application requiring the highest accuracy, consult with your GIS Specialist to manually install the latest transformations in ArcGIS.

See the Datum 101 and DatumSection on this site, and

Consult with your local GIS specialist for the correct settings for your location and data.