BETTER THAN RADAR: Flightradar24.com, which gets its information about planes in the air using Automatic Dependent Surveillance Broadcast (ADS-B) technology, has been widely cited by many reports as it had been tracking the location of MH370 up to the point where its signal disappeared while navigating the border between Malaysia and Vietnam:-
IF you’ve been following the ongoing news surrounding the missing MH370 aircraft, it’s likely you would have come across the name Flightradar24.com.
The site, which gets its information about planes in the air using Automatic Dependent Surveillance Broadcast (ADS-B) technology, has been widely cited by many reports as it had been tracking the location of MH370 up to the point where its signal disappeared while navigating the border between Malaysia and Vietnam.
At the same time, you may also have heard local authorities talk about the use of primary and secondary radar in efforts to pinpoint the exact location of the vanished plane.
In order to understand how they each work, Bytz spoke to Mikael Robertsson, co-founder of Flightradar24, on the differences of these technologies and what information they can provide.
Ongoing broadcasts
“Primary radar is the one used by military. It scans the area for echoes of radar signals so they can see everything,” explains Robertsson.
“Secondary radar works about the same. It also sends out a signal, but when (the) aircraft gets this signal, it transmits a secondary signal back. When you receive the echo, you’ll get radar information that’s from (the plane’s) transponder so you can identify what plane it is. But what information you get depends on what the (plane’s) transponder is transmitting.”
However, the tracking technology powering Flightradar24 is something else altogether, namely ADS-B.
If an airplane’s transponder is ADS-B enabled, the aircraft will automatically broadcast data independent of radar interrogation.
“It’s installed in most aircraft nowadays and it transmits the position of aircraft at every second,” says Robertsson. “To pick up the ADS-B signal, you don’t need to have radar, you just need to have a small radio receiver to get signals of the position of aircrafts. That’s what we are using.”
Information that can typically be obtained from ADS-B signals include a plane’s ID, its current position, altitude, speed and direction.
“With primary and secondary radar, you don’t get information on an aircraft’s speed. You have to calculate it. For ADS-B signals, you can get it directly from the transponder,” he explains.
“ADS-B is something new and it’s not yet used by air traffic controllers. Most aircraft today has these transponders installed. In some parts of the world, it’s starting to get introduced. Australia was the first country to do so.”
He believes it will be rolled out in Asian countries later this or the next year and that it will eventually become mandatory for all aircraft to have ADS-B enabled transponders.
“The first ADS-B enabled transponder was installed in an aircraft about eight to ten years ago. But changes in the aviation industry take a very long time as it has to be extremely safe before it gets widely used.
“It took until December last year before the first country started to (officially) use it. It will take another five to ten years before it’s used globally,” Robertsson says.
Lost in transmission
When asked why Flightradar24 had lost ADS-B signals transmitted from MH370’s transponder past 1.21am on March 8, Robertssson put forth two possible scenarios.
“In this case, either the transponder was turned off or it dropped in altitude. In between Malaysia and Vietnam, our coverage is limited to 30,000 feet (in altitude). If it lost altitude, it could have fallen below our coverage,” he said.
Based on the data Flightradar24 collected on MH370, he says the company saw the aircraft take off from Kuala Lumpur at forty minutes past midnight.
“We could also see it climbing and it was completely normal. In 20 minutes, it had risen to 35,000 feet. It then stayed in this altitude and flew for 20 minutes. The plane was 150km off the coast of Malaysia when the signal from its transponder disappeared,” Robertsson says.
A part to play
Flightradar24 has been using ADS-B for the past six years. According to Robertsson, more and more ADS-B radio receivers are being installed around the world.
“It’s much cheaper to build (ADS-B) coverage,” he says. “Primary and secondary radar costs millions of dollars whereas an ADS-B receiver costs only around US$1,000 (RM3,279.50).”
The maximum range of an ADS-B receiver is 300km, but its signals cannot travel around large objects such as buildings or mountains. However, the range may be greater in favourable weather conditions.
Currently, Robertsson says there are nine ADS-B receivers located within Malaysia that are contributing data to Flightradar24. These receivers are spread out across various parts of the country and are operated by private individuals.
In total, Flightradar24 draws information from 3,200 receivers globally.
“In other parts of the world, we have many more receivers. In places like UK or Germany, we have like over 100 receivers. There are 500 in the United States and around 100 in Australia,” he shares.
Interested parties can actually contribute towards improving ADS-B coverage in Malaysia by setting up their own ADS-B equipment and feeding the data obtained from there to Flightradar24.
More information on how to do so is available on the company’s website at http://www.flightradar24.com/increase-coverage.
– THE STAR
