How to set a custom a Datum


Every mapping system, whether geographic or projected, is defined relative to a specific geodetic datum.

For short, in OnPOZ software, a geodetic datum is called a datum.


 A geodetic datum is modeled using an ellipsoid, which is an approximation of the shape of the Earth.

 In addition, any datum can carry a datum transformation used to relate the datum to the WGS84 reference. This transformation provides a mean to translate coordinates from any datum to any other datum, using WGS84 as the common reference.


While the complete definition of datum involves more parameters, in the software, for practical purposes, it is modeled by an ellipsoid along with its transformation parameters with respect to WGS84



Creating a new Datum

To set a datum which is not part of our predefined list:

On your PC, start OnPOZ Tools and select Mapping System Editor, then click on the Datum button to open the Datum Editor.

From there you can manage your datums: Add... new datums, Edit... existing ones and Delete them.  Note that when you delete a datum, all existing Mapping System based on this datum are also be deleted !


When you click on Add…, the Datum Templates available are displayed.

To create a new datum, select NEW which launches the Datum Editor.

Here are the step to create a new datum:

1. Input a Short Name;

2. Input a Long Name which is the name that will be displayed in all the reports;

3. Input the 7 transformation parameters (Transformation Parameters to WGS84/ITRF00). Please contact your local authority to get the values that reflect your area or country. These parameters are important if you have large discrepancies between your local datum and WGS84/ITRF2000.

4. Rates of Change are not necessary unless you are processing in PPP mode.

5. Finally, select the proper ellipsoid in the drop down box at the bottom of the dialog box.


Here is a list of all supported ellipsoids in OnPOZ software:

A datum cannot be created on the Windows Mobile Device; you need to create it on your PC with OnPOZ Tools.

Once created you will need to update the mapping system list of the mobile application (refer to Modify the Mapping system list for more details).

Article: 000061

Related Products: EZField, EZTag CE, OnPOZ Tools

Last Update: 2017-04-11 18:06:32

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