Topic Author
Posts: 4017
Joined: Sun Jul 31, 2005 11:05 pm

Using The Weather Radar For Navigation

Sat Nov 24, 2007 10:02 am

Hi guys,
I'll limit my question to approach and departure.

There's an increasing number of GPS approach/landing procedures out there. But is there really a backup?

Here goes my question: IIRC most weather radars have a ground mapping function. Couldn't this be used to check the aircraft's position relative to a terrain database? I imagine this would be especially useful at airports located in mountainous terrain, where an ILS can't be installed. Lower weather minimums should be possible.

And maybe it's also useful for low-visibility departures or taxiing?

Is it possible to clearly distinguish the runway surface from other objects with the ground mapping function of a weather radar?
Exceptions confirm the rule.
Posts: 647
Joined: Sat Apr 16, 2005 9:09 am

RE: Using The Weather Radar For Navigation

Sat Nov 24, 2007 10:52 am

The MAP function of the Weather Radar is for showing the surface only and is very low resolution. It doesn't show any man made objects other than in large context like a city. It certainly doesn't show an airport. It's best used to visualize coast lines. However, it's use as a navigation device is strictly prohibited. It can assist in situational awareness or to aid confidence when operating in proximity of a coastline or large mountain.

Many aircraft today have Enhanced Ground Proximity Warning Systems which use a detailed terrain database in conjunction with GPS and can display on some aircraft's weather radar screen. However, this is a depiction from derived data and not a real return of surface features so, again, it's not for use in navigation.
Posts: 551
Joined: Tue Jan 31, 2006 11:58 am

RE: Using The Weather Radar For Navigation

Sat Nov 24, 2007 11:05 am

Quoting A342 (Thread starter):
And maybe it's also useful for low-visibility departures or taxiing?

The legal answer is 'no' to both.

In airline or general aviation operations, the radar is not intended for terrain avoidance. First it is not designed to do so and second it would not show antennas. If you lost your GPS signal during approach, you should have ample information from your charts to know basically which direction you should go to avoid obstacles. The radar MAP might be beneficial for basic orientation but I would hope I would never have to rely on it.
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward" Leonardo Da Vinci

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