Files in DXF format
(Drawing eXchange Format) is a CAD
data file format widely used. Dxf files contain plans to be displayed, edited, sent to a printer, or computer controlled cutting tables. There are several versions of DXF, but I recommend the DXF 2000 because it is compatible with many programs. There are other formats, such as DWG or DGN, but I find most interesting DXF because it is very easy to create graphical objects and text in this format. It is therefore that LEparagliding and other programs have the graphical output in DXF.
To view and edit the DXF you need a special program.
For many years, remains a problem using a CAD program on GNU/Linux or BSD Systems. As a GNU alternative, you can use LibreCAD. But just view and edit in 2D. Several teams of programmers are making a great effort in this regard, working to improve the features of LibreCAD.
Draftsight form Dassault Aviation, works fairly well in 2D and 3D, but the license does not respect your freedom.
AutoCAD 200X is still much better (must be recognized), but has a proprietary license and this is not good.
There are many other programs that can view and edit DXF.