dlgvu is an interactive viewer for Unix, written in the [../../ Icon] programming language. It reads DLG files to produce maps.
Topographic maps of the United States Geological Survey (USGS) are well known to hikers and others. The USGS has digitized many of these maps and published them on the Web as Digital Line Graph (DLG) files in vector form. The USGS developed and released a viewer for these files, but it runs only on Microsoft Windows.