raubtier, Насчет открыть не в курсе а конвертировать можно попробовать при помощи
GPSBabel
GPSBabel convert easely OziExplorerCE *.plt track to gpx. This format is use for upload gps information into osm (use osm for output).
GPSBabel converts waypoints, tracks, and routes from one format to another,
GPSBabel supports the following formats:
Cetus, CoPilot Flight Planner, CSV, Custom CSV, Delorme Street Atlas, Delorme Street Atlas 2004 Plus, Delorms GPS Log, Delorme routes, DNA, EasyGPS Binary, Fugawi, Garmin serial, Geocaching.com loc, GeocachingDB, Geoniche, GPilotS, GPSDrive, GPSman, GPSPilot, gpsutil, GPX, Holux, IGC, Magellan serial, Magellan SD, Magellan Navigator Companion, Mapopolis.Com Mapconverter, Mapsend, Mapsource, Maptech, Microsoft Streets and Trips, Navicache, Netstumbler, NIMA/GNIS Geographic Names, NMEA sentences, OziExplorer, PalmDoc, PCX5, PocketStreets 2002 Pushpin, PSITrex, Quovadis, Tab-separated data, Tiger, TopoMapPro, Topo by National Geographic, xcsv, xmap, xmapwpt.
Попробовать сконвертировать в gpx формат и затем открыть при помощи viking
UPD. Работает.
gpsbabel -i 'ozi,snlen=10,snwhite=1' -f input_filename.plt -o 'gpx' -F output_filename.gpx