Sunday, May 14, 2006

Rosum: A Down-to-Earth Version of GPS

At a recent event, I met someone from Rosum, a company with a new twist on Global Positioning System (GPS) technology. I know nothing about the company’s business outlook, but their technology is a great example of elegant design.

A little background: GPS is the satellite system that allows a receiver to pinpoint his or her position anywhere on Earth. The receiver locates itself by knowing the position of at least three satellites and the time it takes a signal to reach the receiver from each satellite. This page’s section on “2-D Trilateration” has a good explanation of the general concept, which is easier to understand as a two-dimensional example than the GPS system’s 3D version.

GPS works best when a relatively unobstructed path exists from the receiver to the satellites. Thus, reception in areas with hills or high buildings can be problematic, as is reception inside buildings.

Rosum’s plan is to run a GPS-like system using over-the-air television signals, from television broadcast towers. I like the plan because of its elegance at multiple levels:

  • There are already enough broadcast towers around most urban areas, saving a huge amount of time and money that would otherwise go to creating infrastructure.
  • Television signals already include precise synchronization information, which is important for enabling the trilateration.
  • Compared to GPS signals, over-the-air television signals are higher-power and lower-frequency, both of which improve reception indoors and amid uneven terrain.
  • Television towers don’t move, as satellites do; over-the-air television signals’ relatively short path to the receiver are subject to less distortion than satellite signals from space. These factors reduce system complexity.

Of course, Rosum’s “GPS-TV” concept has its own challenges—the company has been around since 2000 working on them. But, like hearing glasses, this is one of those ideas that deserves mention just for its cleverness.

The company plans to make money from a variety of applications, which you can view here. The technology is currently in field testing.


  1. Hi Steve - Thanks for thinking of us. It was a pleasure to find this post. Indeed positioning with TV is not without its challenges! That all said, the world seems to be coming our way. At last, mobile TV is becoming a reality. The full digitization of TV broadcasts is finally happening. TV tuners have come down in power and cost. The macro environment has drastically improved since we first set out to do this.
    One item you may be interested in - the Emergency Alert System. Recall that this uses TV as its backbone. What could be used for Positioning, Navigation and Timing, i.e., all the major functions of GPS? Right here on the ground? How cool would that be?
    Cool doesn't pay the bills...but certainly we have a lot to keep us busy.
    Best wishes -

  2. You can learn more how positioning systems like Rosum TV-GPS work on this website .
    This is website is dedicated to alternative and complimentary positioning technologies to GPS, including TV-positioning.