Earth orbits and satellite coverage display in 3D on your laptop.
SaVi - simulate Starlink, Iridium, Globalstar, O3b, GPS, Galileo and other satellite constellations, modify them, or design your own. Requires Tcl/Tk and Unix libraries; 3D viewing option requires Geomview running on X Window.
surfit is an open source and free gridding and contouring software. surfit can do interpolation/approximation of points, contours and surfaces, can take fault lines and trend surfaces into account, can use inequalities and other conditions. Supports a lo
Ytk is a Tcl/Tk program which adds menus, buttons and features to the basic command line driven Yorick program and language. It also enables usage of all Tcl/Tk widgets and functions including buttons, sliders, checkboxes, and other typical TK widgets to