RADAR, GPS, and ADS-B

RADAR was conceived over 100 years ago, followed not-so-swiftly by GPS in 1994. Now, nearly 20 years on, we have the next wave of technology – Automatic Dependant Surveillance-Broadcast, or ADS-B.

But is this a new technology, or is it simply a way of packaging, understanding, and disseminating the information we already had? ADS-B allows anyone with Internet and a browser - anywhere in the world - to locate and track over half of all the planes in flight at that time. So how did we get here, and what technologies allow this to happen?

In 1989 I started training as a Marine Radar Officer for the merchant navy. I had to fix them – all the way down to finding and replacing faulty components. This, of course, was when you could repair to component level.

When a friend of mine posted a link to a web site that allows you to watch aircraft around the world, in real time, I had to know how it worked. If you're as much of a geek as me you'll be shouting, 'how cool is this technology', and then checking to see no one noticed. If your not, you're probably about to hit the back button.

So how did the technology form to create this wonder of science. To understand it, a little history of the technology that came before is needed...

In the late 19th century, Heinrich Hertz – who's name now denotes cycles per second (particularly when referring to electro-magnetic waves) – was the first to experiment with radio waves reflecting off metallic objects. The inventor Christian Hülsmeyer developed these principles further, but his work allowed radar to identify objects but not to accurately distance them (or 'range' them.) His work was patented in 1909, and he called his system the Telemobiloscope.

During the latter part of the 1930’s, many countries secretly worked on their own versions of radar, but the name 'radar' wasn't used until it was coined by the US navy. When I trained in radar, in the late 80's, I was still working on huge valve-based systems that used very high voltages to produce the high power microwaves. At that time, cell phones were still in their very early stages and GPS wouldn't become operational for another 5 years.

The GPS network of satellites is maintained by the US government, and became operational in 1994. The US provide free access to their data, which allows us all to buy a cheap receiver (usually in our mobile phone) and then pinpoint our position on the planet to within metres. This is an amazing feat by anyone's standards. This level of technology allows us to safely keep over 5000 commercial aircraft in the air above the US at any one time (Dailymail.)

Europe has its own version of GPS, but that's another story.

These images show the aircraft that were in the air as I wrote this article. It states that only 70% of commercial aircraft in Europe (only 30% in the US) carry ADS-B technology. So what is it?

ADS-B is the next generation of Air Traffic Control technology uses conventional GPS technology to gain an accurate position. This position is then re-transmitted by the aircraft with the addition of its own flight data. Other aircraft using the system then receive this information, as does Air Traffic Control. This then gives a far more accurate position than radar, it covers more of the planet than radar, and it isn’t affected by the weather and other meteorological stuff!

From understanding the principles of radio waves, to bouncing them off metal object, and then to creating a working radar system - took over 40 years. The following 50 or so years saw a gradual refinement and improvement on this technology. But now, 25 years on from the last time I repaired a radar, I wouldn't recognise the systems in use today. And to leap forward to the advances that allow a real-time display of almost all of the commercial flights in the air at any one time for anyone to view is astounding.

Where will the next 25 years see this technology progress? One of the selling points of the ADS-B technology is that it's small, cheep, and easy to retrofit, so how small can these things go? How long before we all have them fitted at birth? In 25 years, I'll try to remember to write the follow up article to answer all of these questions!