gpsd is a daemon that listens to a GPS or Loran receiver and translates the positional data into a simplified format that can be more easily used by other programs, like chart plotters. The package comes with a sample client that plots the location of the currently visible GPS satellites (if available) and a speedometer. It can also use DGPS/ip.
np is a compact NMEA parser. It provides quick and flexible access to GPS data from various sources. Data can be read from devices, text files, STDIN, or GPSD (raw mode). The list of supported NMEA sentences includes $GPRMC, $GPGGA, $GPGSA, $GPGSV, as well as Garmin's proprietary $PGRME and $PGRMM. By employing user-definable stylesheets, the parser output can be adapted to numerous application scenarios. The parser can be queried directly from the console or through the included Web front end.