ATC Radar (Digital)
The next generation of ATC radars included some new technology. In this case, the data that was received by the radar antenna was processed by computers and turned into digital data. This way the data could be sent great distances by using modems and satellite links. Now, the ACC's could start spreading radar antennas around without having to man them at each site individually, but could now all operate out of the same building.
The old system in use in Canada, called JETS (Joint Enroute Terminal System) was implemented. This system promised to reduce some workload. By the use of Mode C readouts, controllers no longer had to ask pilots for altitudes on a contunal basis, and could instead ensure on reading is valid and use it from there. This cut down some communication and created some efficiencies with it. Another benefit was data tags. The old systems detected aircraft and displayed them, but even though codes were selectable to an extent, the radar still displayed them (as a single slash if the code was not selected, a double slash if it was selected). The computers involved now could not only display the code, but could also add a data tag showing the controller the aircraft's identification, his altitude and groundspeed. Also, a little two-letter symbol was added just above the target to show who was working the aircraft. This came to our next coordination saving device: A system handoff. Rather than transferring radar identification of a target from one controller to another by using voice ("20 miles west of Moncton is ACA123 at FL240") on a hotline or actually, physically pointing to the target on the receiving controller's screen, a controller could put the target in "handoff mode" which makes it flash on the receiving controller's screen so he knows the airplane is coming his way. A little more savings on communications.
With all the processing power, JETS had its disadvantages. You could only view one radar source at a time, which meant some sectors would constantly switch between sources depending on what airspace they needed to view. Also, in order to provide for a more accurate track on a target, code was introduced for "track smoothing". This worked reasonably for a high speed, enroute target, but was no good for an aircraft on a radar vector to final. The displays we called "time shares" showed analog radar data from nearby sites with digital data superimposed over top of it. It was often seen, especially when an aircraft took a tight turn, that the analog target (what the radar was actually showing) would make the turn, while the digital target (processed by the computers with track smoothing) would continue relatively straight ahead for another sweep or two, then jump to where the target should be. Track smoothing seemed like a good idea, but it was clearly demonstrated that it was not what it was cracked up to be, and ATC had to use 10 NM between targets.
Along came a new system called RAMP. Transport Canada (then operator of the ATC system) built a new system of radar antennas that were designed to be more accurate, totally digital, and included a new processing system in the units that would make use of the data. This system offered a number of advantages over JETS. First and foremost, the systems takes the overall picture from all the radar sources fed into it and "mosaics" them together to make one picture. No more radar source switching. The radar sites themselves all send processed data to the ACCs, so no more complex controls at the sector for the controller. Every gain has it's disadvantages, though, and ATC's weather picture has greatly worsened. The change in wavelength for the primary radar and the digital processing (which means no fine tuning controls for ATC) meant, inadvertently, that the weather display capability was greatly reduced (See previous posts for more on the weather capability).
In any case, the new system was still drawn as a vector display (also mentioned in recent post), and since it was built in the 80's, the computers didn't have much memory. Recent upgrades in the ACC's have led to newer, color, raster displays on 20" square monitors (2048x2048 resolution), much more memory and much more functionality, too.
ATC's radar systems have come a long way over the years. Have I forgotten anything? Want more info on a particular item? By all means, write. I'll see what I can come up with.
The old system in use in Canada, called JETS (Joint Enroute Terminal System) was implemented. This system promised to reduce some workload. By the use of Mode C readouts, controllers no longer had to ask pilots for altitudes on a contunal basis, and could instead ensure on reading is valid and use it from there. This cut down some communication and created some efficiencies with it. Another benefit was data tags. The old systems detected aircraft and displayed them, but even though codes were selectable to an extent, the radar still displayed them (as a single slash if the code was not selected, a double slash if it was selected). The computers involved now could not only display the code, but could also add a data tag showing the controller the aircraft's identification, his altitude and groundspeed. Also, a little two-letter symbol was added just above the target to show who was working the aircraft. This came to our next coordination saving device: A system handoff. Rather than transferring radar identification of a target from one controller to another by using voice ("20 miles west of Moncton is ACA123 at FL240") on a hotline or actually, physically pointing to the target on the receiving controller's screen, a controller could put the target in "handoff mode" which makes it flash on the receiving controller's screen so he knows the airplane is coming his way. A little more savings on communications.
With all the processing power, JETS had its disadvantages. You could only view one radar source at a time, which meant some sectors would constantly switch between sources depending on what airspace they needed to view. Also, in order to provide for a more accurate track on a target, code was introduced for "track smoothing". This worked reasonably for a high speed, enroute target, but was no good for an aircraft on a radar vector to final. The displays we called "time shares" showed analog radar data from nearby sites with digital data superimposed over top of it. It was often seen, especially when an aircraft took a tight turn, that the analog target (what the radar was actually showing) would make the turn, while the digital target (processed by the computers with track smoothing) would continue relatively straight ahead for another sweep or two, then jump to where the target should be. Track smoothing seemed like a good idea, but it was clearly demonstrated that it was not what it was cracked up to be, and ATC had to use 10 NM between targets.
Along came a new system called RAMP. Transport Canada (then operator of the ATC system) built a new system of radar antennas that were designed to be more accurate, totally digital, and included a new processing system in the units that would make use of the data. This system offered a number of advantages over JETS. First and foremost, the systems takes the overall picture from all the radar sources fed into it and "mosaics" them together to make one picture. No more radar source switching. The radar sites themselves all send processed data to the ACCs, so no more complex controls at the sector for the controller. Every gain has it's disadvantages, though, and ATC's weather picture has greatly worsened. The change in wavelength for the primary radar and the digital processing (which means no fine tuning controls for ATC) meant, inadvertently, that the weather display capability was greatly reduced (See previous posts for more on the weather capability).
In any case, the new system was still drawn as a vector display (also mentioned in recent post), and since it was built in the 80's, the computers didn't have much memory. Recent upgrades in the ACC's have led to newer, color, raster displays on 20" square monitors (2048x2048 resolution), much more memory and much more functionality, too.
ATC's radar systems have come a long way over the years. Have I forgotten anything? Want more info on a particular item? By all means, write. I'll see what I can come up with.
posted by Michael at
07:45
