Rosum has raised $15 million to invest in its navigation technology which is an alternative to global positioning system (GPS).

The Redwood City, Calif., company uses signals embedded in broadcast TV signals to fix the location of different moving objects. It serves as an alternative to GPS because it works in areas where GPS devices can’t get a clear view of satellites in the sky.

The company is focusing its efforts on femtocell, voice-over-Internet protocol (VoIP), and first-responder and defense applicattions.

Existing investors Charles River Ventures, Allegis Capital, Steamboat Ventures and KTB Ventures participated in the round. A new investor, TruePosition, Inc., a subsidiary of Liberty Media Corporation, also joined in the round. Skip Speaks, CEO, said in a statement that the new money will let the firm expand into mobile TV and femtocell (where a small cell station extends service coverage indoors).

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