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ATC Radar Question
I understand that ATC radar uses an encoding altimeter and a transponder
operating with Mode C to determine an aircraft's altitude. Let's forget about Mode C for a moment and switch to Mode A only or just a primary return. If an aircraft is at 18,000 ft (approx 3 nm) and 3 nm away from the radar antenna, as seen on a map, how does the radar correct for slant distance when distance is displayed (e.g. using concentric circle distance markers on the scope or relative to a known distance, such as a marker on the display)? In other words how does the radar know that the aircraft is actually 3 nm away laterally and not 4.25 nm (approx slant distance at that altitude)? |
#2
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ATC Radar Question
"Jackie" wrote in message ... I understand that ATC radar uses an encoding altimeter and a transponder operating with Mode C to determine an aircraft's altitude. Let's forget about Mode C for a moment and switch to Mode A only or just a primary return. If an aircraft is at 18,000 ft (approx 3 nm) and 3 nm away from the radar antenna, as seen on a map, how does the radar correct for slant distance when distance is displayed (e.g. using concentric circle distance markers on the scope or relative to a known distance, such as a marker on the display)? In other words how does the radar know that the aircraft is actually 3 nm away laterally and not 4.25 nm (approx slant distance at that altitude)? Asquared + B squared = C squared, I'd guess. |
#3
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ATC Radar Question
Matt Barrow wrote:
"Jackie" wrote in message ... I understand that ATC radar uses an encoding altimeter and a transponder operating with Mode C to determine an aircraft's altitude. Let's forget about Mode C for a moment and switch to Mode A only or just a primary return. If an aircraft is at 18,000 ft (approx 3 nm) and 3 nm away from the radar antenna, as seen on a map, how does the radar correct for slant distance when distance is displayed (e.g. using concentric circle distance markers on the scope or relative to a known distance, such as a marker on the display)? In other words how does the radar know that the aircraft is actually 3 nm away laterally and not 4.25 nm (approx slant distance at that altitude)? Asquared + B squared = C squared, I'd guess. And how does it separate A and B? |
#4
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ATC Radar Question
Jackie wrote:
I understand that ATC radar uses an encoding altimeter and a transponder operating with Mode C to determine an aircraft's altitude. Let's forget about Mode C for a moment and switch to Mode A only or just a primary return. If an aircraft is at 18,000 ft (approx 3 nm) and 3 nm away from the radar antenna, as seen on a map, how does the radar correct for slant distance when distance is displayed (e.g. using concentric circle distance markers on the scope or relative to a known distance, such as a marker on the display)? In other words how does the radar know that the aircraft is actually 3 nm away laterally and not 4.25 nm (approx slant distance at that altitude)? Absent something else, it doesn't. All a primary paint radar knows is azimuth and slant range. -- Jim Pennino Remove .spam.sux to reply. |
#5
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ATC Radar Question
Jackie wrote:
If an aircraft is at 18,000 ft (approx 3 nm) and 3 nm away from the radar antenna, as seen on a map, how does the radar correct for slant distance when distance is displayed (e.g. using concentric circle distance markers on the scope or relative to a known distance, such as a marker on the display)? Without altitude information from the pilot or a Mode C transponder, the radar system can't extract the horizontal distance from the slant distance. Where did you read that their systems correct for altitude without Mode C transponders? If they could do that then they wouldn't have ever needed the transponders to report altitude. |
#6
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ATC Radar Question
Jim Logajan wrote:
Jackie wrote: If an aircraft is at 18,000 ft (approx 3 nm) and 3 nm away from the radar antenna, as seen on a map, how does the radar correct for slant distance when distance is displayed (e.g. using concentric circle distance markers on the scope or relative to a known distance, such as a marker on the display)? Without altitude information from the pilot or a Mode C transponder, the radar system can't extract the horizontal distance from the slant distance. Where did you read that their systems correct for altitude without Mode C transponders? If they could do that then they wouldn't have ever needed the transponders to report altitude. So if a pilot turns his Mode C from off to on, does the radar then correct the distance plotted (less distance from the antenna) based on the altitude reported? |
#7
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ATC Radar Question
Jim Logajan wrote:
Jackie wrote: If an aircraft is at 18,000 ft (approx 3 nm) and 3 nm away from the radar antenna, as seen on a map, how does the radar correct for slant distance when distance is displayed (e.g. using concentric circle distance markers on the scope or relative to a known distance, such as a marker on the display)? Without altitude information from the pilot or a Mode C transponder, the radar system can't extract the horizontal distance from the slant distance. Where did you read that their systems correct for altitude without Mode C transponders? I don't believe I indicated I read this. If they could do that then they wouldn't have ever needed the transponders to report altitude. Does precision approach radar require a transponder to report altitude? |
#8
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ATC Radar Question
Clark wrote:
Jackie wrote in : [snip] Does precision approach radar require a transponder to report altitude? PAR uses a height finder radar to provide sufficient vertical resolution for precision approaches. Could you elaborate on how the "height finder" works? |
#9
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ATC Radar Question
Jackie wrote:
Clark wrote: Jackie wrote in : [snip] Does precision approach radar require a transponder to report altitude? PAR uses a height finder radar to provide sufficient vertical resolution for precision approaches. Could you elaborate on how the "height finder" works? the elevation radar determines altitude the same way the azimuth radar determines bearing. |
#10
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ATC Radar Question
On Fri, 12 Jun 2009 03:54:29 +0000 (UTC), Clark
wrote: Jackie wrote in : [snip] Does precision approach radar require a transponder to report altitude? PAR uses a height finder radar to provide sufficient vertical resolution for precision approaches. Mode C only provides 100 foot altitude resolution. bzzzzt! Mode C provides a height eg 1252ft which is deemed only accurate to 100ft because the calibration errors are limited to 100ft. |
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