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.

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?

I don't think that altitude from the ModeC is ever factored into where to
plot the target. The target was always slant range.
BT

"Jackie" wrote in message
...
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?

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?

"Jackie" wrote in message
...
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?

At the altitudes involved during approach, it's not so critical (altitude is,
but not the angle), but during
approach the heading data is as critical as the altitude reporting.

reported altitude from a ModeC transponder is never used for vertical
guidance on a PAR approach.

"Matt Barrow" wrote in message
...
"Jackie" wrote in message
...
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?

At the altitudes involved during approach, it's not so critical (altitude
is, but not the angle), but during
approach the heading data is as critical as the altitude reporting.

In article ,
Jackie wrote:

Does precision approach radar require a transponder to report altitude?

No.

The beauty of the PAR approach is the aircraft only needs a
functioning radio.

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?

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.

"Bob Noel" wrote

the elevation radar determines altitude the same way the azimuth radar
determines bearing.

There are actually two radars running for PAR, right? One sweeping left to
right and one sweeping up and down, I think.
--
Jim in NC