Using Tcl/Tk to Program a Full Functional Geographic Information System

Tcl/tk is used to provide programming constructs and easy to build graphical user interfaces for a full functional Geographical Information System (GIS). This paper defines the term GIS, explains why tcl/tk is used, discusses which extensions to tcl/tk are used, and describes what extensions are added to support the GIS. Examples are provided. The GIS system is part of a commercial product family internally referred to as Harbour GIS (HG). Tcl/tk and the GIS extensions are used to build common graphical user interface widgets for GIS program developers and to build GIS specific applications for GIS end users. This paper presents the extensions using simple examples that should be easy to follow without need for specific domain knowledge. By presenting simple examples of how the extensions are used, it is hoped that others may gain insights into how one commercial vendor has approached adding significant functionality to tcl/tk.