"Dan Luke" wrote in message
...

Yes, that is a disadvantage of their system. But it looks like WSI's map
is
not a moving map that will show the position and direction of the
aircraft,
a big disadvantage, IMO - is that true?

That is true if you use a laptop as the display for the WSI system -- then
then again, a laptop is not even a display option for the Bendix/King
system.

If you connect the WSI system to an MFD then the MFD already has your
position on the map.


http://www.bendixking.com/static/bro...pdf/KDR510.pdf which shows the
MFD depicting NEXRAD base reflectivity. Looks just like what I see on
Intellicast. The unit also gives graphic METARS, etc.

NEXRAD base reflectivity is the raw data from each data site; weather
datalink vendors then merge this data to create a composite national or
regional image. There is quite a bit of proprietary digital image
processing involved -- that is why, for example, weather on
www.intellicast.com looks different from weather on
www.theweatherchannel.com etc. The color coding can be different, some
vendors may choose to delete returns under 10dB or under 15dB, and some
vendors have different processes to remove ground clutter by either manual
or automated techniques.

The bottom line is that for the critical decision of deciding whether a
given area of Level 3 weather is convective or benign, it is a big help to
have experience with that particular source of weather data. The WSI system
lets you learn about their image processing on the ground via the Internet;
the Bendix/King system only lets you learn by trial-and-error in the air.


My main concern about the satellite systems is still the bandwith
question.
B/K had a pretty convincing demonstration of how other venders'
bandwith-saving software tricks could cause innacurate weather images.
Also,
due to limited bandwidth, map resolution was not as good on the satellite

I saw the demonstration too, and my impression was that this degree of
accuracy only mattered to a turboprop or jet pilot attempting to penetrate a
line of thunderstorms, in which case he ought to have high-power vertical
profiling radar as well -- not an issue likely to be relevant to most of the
piston IFR pilots on this group, myself included. Far more important to me
is the ability to get an accurate view of the weather on the ground before
takeoff and in the initial climb segment of my flight... the Bendix/King
system may be more accurate, but its data is simply unavailable for these
important portions of flight or during flight planning. If I can plan
early and request a routing to give me a good margin around the weather,
then it really does not matter if my image has slightly less resolution
compared with an alternate system which only works above a given altitude.

One of the best advantages of weather datalink is the ability to depart from
a small airport which has no weather resources and be able to make a
pre-flight decision on flying around/through areas of convective activity.
A satellite-based system such as WSI works great for this purpose at any
airport; the Bendix/King system will often be completely unavailable on the
ground in the same situation.

--
Richard Kaplan, CFII

www.flyimc.com