Graphic Technologies, Inc. (GTI) GTViewer Reader/Writer

Licensing options for this format begin with FME Desktop Professional Edition.

Note: For more information on this format, please visit the Graphic Technologies, Inc. website at

The GTI GTViewer Reader and Writer modules provide FME with access to Graphic Technologies, Inc.’s (GTI’s) GTViewer Format.

The GTViewer format is used by a number of GTI products, including:

  • GT/Field
  • GTCreate
  • GTData
  • GTRead
  • GTViewer .NET Control
  • GTViewer Data Server
  • GTViewer for Android
  • GTViewer for iOS
  • GTViewer for Windows
  • GTVx
  • GTWeb Server
  • Pocket GTViewer .NET Control


The GTViewer format stores both geometry and attribute information for spatially organized features.

GTViewer data consists of a .GTM file (GTViewer Manager File) plus a collection of files that are referenced by the .GTM file, including graphics files, index files, query files, tabular data files, color files, fonts, linestyles, style definitions, etc.

File Extension


Module Support


Unextracted Data File



Extracted Data File

Read (session graphics only)


Graphic File/Export file

Read and Write (as part of .GTM output).

A summary of the GTViewer Data file types is shown below:

File Type



Graphics File (Binary File)

  • Contains GTViewer Graphics elements and any embedded data for a single GTViewer category.
  • Can be imported and exported by GTViewer for Windows, GTVx, GTViewer for iOS/Android, and the .NET Controls.
  • All geometry information is stored in this file type.
  • Can be read directly by the Reader module and can be created by the Writer module.


Spatial Index File (Binary File)

  • Spatial index for a single .GTG file or GTViewer category.
  • Used to increase rendering performance.
  • Generated by the Writer module (or the GTIndex utility).


Font Definition file (Binary File)

  • Contains font information for one GTViewer text or symbol font.
  • Used by the Reader module to get specific origin information for symbols.
  • TrueType Fonts (.TTF) can also be used with .DFN fonts, or instead of .DFN fonts.


Color Definition File (ASCII File)

  • Maps color ID values to RGB component color values.
  • Used by the Reader module to get color information for each element.
  • Created or updated by the Writer module.
  • Color information can also be defined in Style Definitions (Style.def); the color.txt file is not necessarily used.


Display Filter Definition Files (ASCII File)

  • Contains default display settings (display status, min display threshold, max display threshold, select-ability, snap-ability) for each Filter ID in a single GTViewer category.
  • Created or updated by the Writer module.
  • Filter Id can also be used to map Style Definitions to Elements. Style Name Mapping is the other.


Range Definition File (ASCII File)

  • Contains the default data set range for a dataset.
  • Created by the Writer module.
  • Values are always defined in GTViewer system units.


Tabular Data File (ASCII File)

  • Pipe delimited tabular data values with corresponding table schema.
  • Contains one or more tables.
  • Created by the Writer module.

Tabular Data Definition File (ASCII File)

  • Schema Definition for all tables contained in the Tabular Data File.
  • Includes all alternate names, display priorities for tables and attributes.
  • Created by the Writer module.


Tabular Data Index file (Binary File)

  • Index file for Tabular Data File.
  • Indexes records in Tabular Data File by primary key(s).
  • Created by the Writer module (or the GTAsciiIndex utility).