How to set a custom Datum

Article: 000006

Related Products: EZSurv

Last Update: 2017-04-05 20:55:21

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From there you can manage your datum by creating new ones, editing existing ones and delete them. Note that when you delete a datum, all existing Mapping System based on this datum will also be deleted!

 

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

To create a new datum, simply select NEW; the Datum Editor will then be displayed.

Datum

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

For short, in EZSurv, a geodetic datum is called simply 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, for all practical purposes, it is modeled in the software by an ellipsoid along its transformation parameters with respect to WGS84.

Creating a new Datum

To set a datum which is not part of our predefined list, go to Tools > Mapping Systems > Editor… (or click on   ), then click on the Datum button. You will get the Datum Editor dialog box.

Here are the steps to create a new datum:

1. Enter a Short name;

2. Enter a Long name (this is the name that will be displayed in all the reports);

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

4. Rates of changes do not have to be input unless you are dealing with PPP;

5. Finally, select the proper ellipsoid in the drop-down list at the bottom of the window.

 

Below you can find a table presenting all the supported ellipsoids: