The Geodetic Datasource

Geographic Imager includes an extensive geodetic parameter database called the Geodetic Datasource. It contains all the latest updates from the widely used EPSG Geodetic Parameter Dataset maintained by the Geodesy Subcommittee of OGP (International Association of Oil and Gas producers) as well as custom systems maintained by Avenza.

In addition, the Geographic Imager Geodetic Datasource supports your custom definitions and allows you to import external WKT (Well-Know Text) and PRJ (Esri projection file) parameter files.

Over 3500 pre-defined coordinate systems are readily available for use in most cartographic projects. Even though the current list of systems is comprehensive, there may be instances where the end users may wish to add a brand new coordinate system to meet their particular needs, or perhaps to duplicate and modify an existing definition to

change the units for example. A complementary Avenza Projections Guide is installed with Geographic Imager. It describes all the projections and datum shifts methods supported by Geographic Imager, to assist users in the process of creating or editing a coordinate system.

The default parameters installed with Geographic Imager are stored within read-only XML database files referred to as the Geodetic Datasource (files named geodata.xml and avenza.xsp). The base data source files shipped with Geographic Imager are installed in the Data Source Files folder at the following location:

Windows: C:\Program Files\Avenza\Geographic Imager\Data Source Files

Mac: /Applications/Avenza/Geographic Imager/Geographic Imager Plug-in/Data Source Files

Geographic Imager allows the creation of custom definitions where parameters are stored in a separate XML file that can be saved or loaded—named customsystems_v2.xml by default. It is recommended to use the default name and default save location as Geographic Imager will have an option to keep a backup of these files when uninstalling (Windows only) or re-installing. The backup files are located in:

Windows: C:\ProgramData\Avenza\Geographic Imager

Mac: /Applications/Avenza/Geographic Imager/Data Source Backup

Geographic Imager will also create a file called customsystems_v2.xvw. This view file stores the organization and folder structure of your custom coordinate systems within the geodetic data source. This file will also be included in the above locations when uninstalling (Windows only) or re-installing.

For Mac users, to restore the geodetic data source, copy the backup files from the backup folder to the appropriate locations. For Windows users, the custom geodetic data source is restored automatically if the option to backup files was chosen during the uninstall process.

Load Custom Coordinate System

A geodetic data source or coordinate system database can be loaded into Geographic Imager, greatly extending the coordinate systems available for use. From the Geographic Imager panel options menu, click Load Coordinate Systems and browse for a geodetic data source.

When loading a custom coordinate system, remember that an accompanied schema file named geocalc.xsd must be present with the XML file. If not present, the geocalc.xsd file can be copied from the Data Source Files folder located in:

Windows: C:\Program Files\Avenza\Geographic Imager\Data Source Files

Mac: /Applications/Avenza/Geographic Imager/Geographic Imager Plug-in/Data Source Files

Edit Custom Coordinate System

Geographic Imager can be extended to support custom coordinate systems. By editing the geodetic data source, it is possible to transform coordinates to and from a coordinate system that is based on a standard map projection but is not predefined within Geographic Imager. To edit a custom coordinate system, click Edit Custom Coordinate Systems in the Geographic Imager panel options menu.

At the top of the Edit Custom Coordinate Systems dialog box, two directory paths are listed: the geodetic data source path and the custom data path.

 The geodetic data source file is protected (read-only). Any additions or modifications to coordinate systems are stored in a separate XML file called customsystems_v2.xml.

On the left-hand side of the dialog box is the data source object folders. To expand a folder to see its subfolders, click the plus sign (Windows) or arrow (Mac) to the left of the category name. To see the entries at any particular level of category, click the category itself. When an object, folder, or subfolder is selected, the data source objects list box to the right displays the information stored within each one. User-defined coordinate system objects can be organized using drag-and-drop between folders. Columns can be resized and sorted alphabetically/numerically.  Right-click on a column header to show or hide it. Entries loaded from the main geodetic data source will be shown in black text, while entries from the custom data file will be shown in blue.

To create a new folder, click the New Folder button. A new folder will be titled "New Folder" by default and can be renamed. Subfolders can also be created using the same method. Only user-defined categories can be deleted using the Delete Folder button.

Create New Data Source Objects

In the Edit Custom Coordinate Systems dialog box, click the New Object button to create a new data source object. When creating new data source objects, the identification information and definition parameters need to be completed. Complete this information in the respective Identification and Definition tabs.

The Identification tab is used to name the object and associate identification codes with it (if applicable). It is important to enter an appropriate name for the object. The Remarks field can be used to add notes on a definition and is optional. The Identifiers list may be used to add identifying codes for an object that may come from other databases. The GC code is a unique identifier assigned by Geographic Imager and should not be altered. To enter additional codes use the space below it. When using automation, the Issuer and Issuer codes are used to identify coordinate systems. For a complete list of EPSG codes, visit www.spatialreference.org.

The Definition tab is used to define the parameters of an object. Each object has parameters unique to it. Refer to the list below when creating new objects.

 Refer to the Avenza Projections Guide for more information on supported projections and their parameters as well as supported datum transformations methods.

Edit Objects

To edit a custom or user-defined object, click the Edit Object button. Edits may be made in the respective object editor dialog box. Alternatively, double-click an object to open the editor dialog box. When a data source object belonging to the master data set is selected, the Edit Object button is disabled (because these objects are read-only). To modify an original object, create a copy of the object first then edit it.

Delete Objects

When a data source object belonging to the master data set is selected, the Delete Object button is disabled. Only user-defined objects can be deleted.

Copy Objects

Any object can be copied. To create a copy of an object, select an object and click the Copy Object button. A dialog box will appear with "Copy of:" preceding the object name in the Name box.

Move Objects

Any user-defined object can be moved. Drag-and-drop an object from the Data Source Objects List to a Data Source Object Folder. A dialog box will prompt you to move the object or to create a shortcut to it.

Load Coordinate System Definitions

In some instances, the coordinate system of an image is not listed in the geodetic data source or the reference file format does not support the coordinate system. In such cases, it may be useful to load custom coordinate system definitions. In the Geographic Imager panel options menu, click Load Coordinate System. Geographic Imager can use the following coordinate system file formats: WKT definitions (.wkt), MapInfo MAP files (.map), MapInfo TAB files (.tab) and Esri projection files (.prj).

 When a coordinate system is loaded from a file (WKT or PRJ), it is added to the geodetic data source but not saved. If the loaded file matches an existing definition, the original definition will be used and the loaded definition will not be added. All new definitions are located at the top level of the appropriate category in the Coordinate Systems folder list (in either Geodetic or Projected). Before exiting Adobe Photoshop, be sure to save your geodetic data source if you wish to use the coordinate system definition again. This can be done through the Edit Custom Coordinate System option.