WxWorx or Anywhere Wx

In article ,
"Jim N." wrote:
The downlink systems are really in their infancy, and it is obvious that the
manufacturers are struggling to keep up with the technology, particularly
with the ponderous bureaucratic certification process imposed by the FAA.
There is no "best" established technology.

Weather uplink has been around for a little while, but the certification
process undoubtedly adds quite a bit of delay and, obviously, quite a
bit of cost. That's why the non-certified portable systems (whether
from Garmin, WxWorx, or a PDA software vendor) have eclipsed the
certified systems when it comes to weather uplink.

The "rat's nest of wires" really isn't the case so much anymore with the
portable systems. With some simple cable management for power, I can
get pretty close to no visible wires. Obviously not as clean as having
everything tucked into the panel, but far from a "rat's nest," and a
heck of a lot less expensive for the exact same information, which is
probably the single largest reason why I invested in a portable system
(it never leaves the airplane).


JKG

Jim N. wrote:

You are correct. Garmin claims that with some upcoming changes the full
functionality of the data downlink will become available. Of course, we've
been waiting for WAAS and terrain for over two years now, with no firm
delivery in sight.


I was told a number of months back that this is included in the WAAS
upgrade. That was while the upgrade was still scheduled for...well...right
about now.

- Andrew

On 9-Jul-2005, Jonathan Goodish wrote:

The bottom line is that you pay a good bit of money for a certified
receiver that to pair with a certified GPS that is unable to display
most of the available weather products. Both the Garmin 396 handheld
and the various PDA/TabletPC solutions provide more bang for the buck
for weather uplink in this scenario.


Please correct me if I am wrong, but I do not believe that the FAA has any
certification criteria -- or requirements -- for use of weather avoidance
equipment in IFR flight. Certainly there is no "slash suffix" (e.g. "/G"
indicates GPS capability) to indicate weather avoidance gear on the IFR
flight plan. So it really doesn't matter whether the GPS providing input
for display of weather info is certified or not.
--
-Elliott Drucker

In article OGXze.6050$xB6.2348@trnddc03,
wrote:
Please correct me if I am wrong, but I do not believe that the FAA has any
certification criteria -- or requirements -- for use of weather avoidance
equipment in IFR flight. Certainly there is no "slash suffix" (e.g. "/G"
indicates GPS capability) to indicate weather avoidance gear on the IFR
flight plan. So it really doesn't matter whether the GPS providing input
for display of weather info is certified or not.


My comments were referring to the hardware itself, that being the GDL69
paired with a Garmin 430/530, not the operation of the hardware. As far
as I know, weather avoidance is the pilot's responsibility, not the
FAA's.

My point was that you can pay $5000 for the GLD69 to pair with your
existing 430/530 installation, or you can pay $2500 for a PDA or Garmin
396 that can display more weather data than can be displayed on the
430/530.



JKG

"Jonathan Goodish" wrote:

In particular, since the NEXRAD provided is base reflectivity, ...

Not exactly true. Here's what WxWorx has to say about it (with minor
paraphrasing):
------------------------------------------------------------------------------------------------------
WxWorx develops their own version of a composite radar picture using the 124
nm base reflectivity from each radar scan (revolution). They arbitrarily
undertake compositing at a five minute interval, compositing the latest scan
and going back in time so that all previous elevations are included (if
there are 14 "cuts" conducted by the radar and it is currently on "cut 4",
we include the latest cut, 4, then all others). The composited image from
each radar is then mosaic-ed for the whole U.S. image."

Each elevation scan or revolution produces a product called base
reflectivity. On a 5 minute schedule, WxWorx uses the most recent scan and
the previous 13 revolutions to build the composite reflectivity image. The
timing is arbitrary which means that the most recent scan may be at some
middle elevation. So when the timer goes off, they just dive in and grab the
last scan that completed and the previous 13. Essentially they have
"considered" all elevations by using this method.

The color of the pixel that gets displayed on your screen depends on many
factors. They look at each elevation over the last 13 revolutions (or 5
minutes) and choose the highest reflectivity value. This could have been
from the latest scan or from the oldest scan. You just don't know. They do
this for the entire 124 nm radius. There are other factors that I have not
mentioned that may change what you see (such as clutter filtering.

This is different than the composite reflectivity seen from the NWS SSR-88D
display. WxWorx does not try to align itself with the Scan 1 to Scan N
(called a volume coverage pattern) composite reflectivity image. Obviously
this makes good sense since they are trying to be schedule driven, not
product driven. In most cases, they will produce a product that is taken
from two volume coverage patterns. But who cares? Each elevation is
considered and they can provide the most current product.
--------------------------------------------------------------------------------------------

They refer to each scan as "base reflectivity", no matter what elevation the
radar is tilted to. The point is that the colors you see in your airplane
represent the highest level of all the different elevations scanned for that
area.

-Mike

In article ,
"Mike Murdock" wrote:
They refer to each scan as "base reflectivity", no matter what elevation the
radar is tilted to. The point is that the colors you see in your airplane
represent the highest level of all the different elevations scanned for that
area.


I'm not sure of the source of your information, since you didn't provide
a direct reference, and it doesn't seem to appear on the WxWorx web
site. Certainly, none of the information that WxWorx provides on their
web site confirms that a composite reflectivity image is provided, and
the information that you provide suggests that the image is a base
reflectivity image with some "educated guessing" involved in order to
attempt to paint a composite-like picture using some base reflectivity
data. However, I'm not a radar expert, so perhaps I'm misinterpreting
something along the way.

I have never put the WxWorx and NWS products side by side to see how
they compare. I would be interested to hear from anyone who has done
such a comparison. WxWorx seems to be somewhat guarded about the
details, or at least I haven't found a good source for the details yet.

I have heard that WxWorx does a pretty good job of painting the heavy
and severe stuff with yellows and reds, but I've personally had some
yellow cells sneak up on me all of a sudden in a sea of green. Seems
that echo tops (which I had turned off at the time) may have shown a
higher-level return before the cells actually painted yellow on the
NEXRAD image.



JKG