After circling the globe for 17 years, GPS satellites will soon have plenty of company. Four countries and the European Union are getting ready to insert over 100 new satellite vehicles (SV’s) into earth orbit.

The good news is that accuracy, coverage and reliability could skyrocket. On the other hand, the new satellites face the same conflict now boiling between GPS and the cell phone industry: interference. One carrier wants to erect 40,000 new cell towers---each a potential threat to GPS receivers. When all the new nav satellites reach orbit, they face the same problem. Because they’ll fly in close formation they also raise the specter of “EMC” (electromagnetic compatibility).

Yet another concern is interoperability, which translates to: “Will they ever make one aircraft radio that can understand six different satellite languages---and not cost more than the airplane?” The international aviation community is just now awakening to these problems.

Despite all the new activity, some people raise the question, do we need all these systems when one should be sufficient? It recalls the early struggle to adopt a VOR standard just after WW2, where two nations (US and Britain) submitted competing technologies for approval. The same happened with TCAS (collision avoidance), where dissimilar designs led to years of delay. The conflicts were resolved when world standards were selected after evaluation by the International Civil Aviation Organization (ICAO). Any other outcome certainly would have crippled the growth of aviation.

Is history repeating for satellite navigation? The usual reason given for the proliferation of so many systems is military security; no nation wants another country to have its hand on the “off” switch. There is also strong motivation by nations to hone their own skills in electronics, aeronautics, and propulsion---the price of membership in the space club.

A good lesson is to move the clock back to 1910, during the “Wild West” of radio. Signals of ships, ham operators and communications carriers were spilling all over the spectrum. Before transmitting, an operator stealthily tuned his radio, listening for a “hole.” Clear spots were hard to find as ancient spark transmitters splattered signals over many megacycles. That chaos came to an end when the world convened the International Telecommunications Union to, as they said, “set the ground rules for a wireless world.”

Could the 1900’s scenario play again today? Imagine an airplane equipped with GPS---it flies 4,000 miles and prepares to land. Fuel is low and weather is so bad that meteorology is reporting “EDAW” (Even the Ducks are Walking). There’s no airport above landing minimums within 400 miles. The Captain requests a GPS approach to Runway 27. The controller replies, “Sorry, sir, all our approaches are Galileo. Proceed to your alternate.”

Fortunately, the signs are that we’ll avoid that drama. An early effort began in 2001 when the United Nations created the “International Committee on Global Navigation Satellite Systems” (ICG).

One working group met in Tokyo last month to deal exclusively with the two problems mentioned earlier; interoperability and compatibility.

In another development, the Institute of Navigation at a recent meeting in Oregon discussed the potential for interference among satellites. One speaker warned that by the year 2020 more than 100 satellites will be operating in the same frequency band. He estimated that up to 35 satellites might be simultaneously in view at any one location on earth.

Manufacturers are also looking ahead by introducing chipsets that receive more than one system. Now being offered are varying combinations of GPS, Galileo and GLONASS. It will be a long road toward GNSS harmonization, but we’re off to a good start.

(Your comments are invited.)