Some ADS-B weather questions

kicktireslightfires

kicktireslightfires

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kicktireslightfires
Hi, Just a few quick questions for you awesome people!
  1. Does ADS-B coverage fully cover the continental USA or are there dead zones?
  2. Do the METARs get updated in real-time on the Dynon 10” display if it has ADS-B in and out, or do you have to manually refresh them somehow?
  3. This page (https://www.faa.gov/nextgen/programs/adsb/pilot/) says the FAA “added six new weather products to the FIS-B service” in including lightning, turbulence, icing, cloud tops… and that “Pilots will have access to the new FIS-B products when their individual avionics are updated.” What do they mean by “updated?” Does that mean when the software is updated? Is that done at every Annual? And does anyone know how long ago the FAA added those six new weather products to the FIS-B? How does one know if an aircraft is capable of and is indeed receiving FIS-B?
  4. What are the advantages for getting SiriusXM Weather vs. the free ADS-B weather?
 
  1. You can find a coverage map on the FAA web site. Coverage varies by altitude, but covers much of the US.
  2. METARs and other weather products should update automatically as ADS-B in receives periodic data streams.
  3. Firmware or software must be updated on your ADS-B device to take advantage of new ADS-B products. This can be done anytime new software is made available by the manufacturer. You may be required to do this at an installer or dealer facility.
  4. XM is satellite based, so you can get it on the ground. ADS-B won't become available until 1500-2000 AGL or so. Personally, I've found XM weather to be rock solid. The ADS-B streams are more flaky, and if towers go off line, you can lose coverage. It's getting better, but I've had days where Nexrad was not available on my device, fortunately on VFR days. Lately it's been more consistent. Of course, XM costs and you need a special receiver. I pipe XM into a ship powered portable GPS I've had for a while. ADS-B shows up on my NGT-9000 and tablet devices.
 
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Agree with the other post plus FIS-B weather precision varies with distance from the ground tower. That is, for example, radar imagery from greater than 250 miles (?) is more coarse than from the local tower. For slow aircraft that may not be a big deal but for faster flyers and long distance flights the more precise NEXRAD data at a distance (as available through XM) can make for better flight planning. Also, here in the west, as said above, the ADS-B towers may not be received until one is very high AGL and at non-flight levels there are still gaps in coverage. There are also some differences in products and timliness of availability between FIS-B and SiriusXM. I suggest you search for FIS-B and SiriusXM on the internet to see the similarities and differences.
 
chemgeek said:
  1. You can find a coverage map on the FAA web site. Coverage varies by altitude, but covers much of the US.
  2. METARs and other weather products should update automatically as ADS-B in receives periodic data streams.
  3. Firmware or software must be updated on your ADS-B device to take advantage of new ADS-B products. This can be done anytime new software is made available by the manufacturer. You may be required to do this at an installer or dealer facility.
  4. XM is satellite based, so you can get it on the ground. ADS-B won't become available until 1500-2000 AGL or so. Personally, I've found XM weather to be rock solid. The ADS-B streams are more flaky, and if towers go off line, houblose coverage. It's getting better, but I've had days where Nexrad was not available on my device, fortunately on VFR days. Lately it's been more consistent. Of course, XM costs and you need a special receiver. I pipe XM into a ship powered portable GPS I've had for a while. ADS-B shows up on my NGT-9000 and tablet devices.
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Many thanks, chemgeek! Do you know if the Dynon displays/indicate when it is and when it is not receiving all ADS-B data?

What about plane-to-plane ADS-B? You said ADS-B doesn't' become available until 1500-2000 AGL, so you wouldn't be able to get ADS-B in traffic until at least 1500 AGL?
 
Arrow76R said:
Agree with the other post plus FIS-B weather precision varies with distance from the ground tower. That is, for example, radar imagery from greater than 250 miles (?) is more coarse than from the local tower. For slow aircraft that may not be a big deal but for faster flyers and long distance flights the more precise NEXRAD data at a distance (as available through XM) can make for better flight planning. Also, here in the west, as said above, the ADS-B towers may not be received until one is very high AGL and at non-flight levels there are still gaps in coverage. There are also some differences in products and timliness of availability between FIS-B and SiriusXM. I suggest you search for FIS-B and SiriusXM on the internet to see the similarities and differences.
Click to expand...

Thanks! Will do! How does one know if the Dynon SV-ADSB-472 receiver receives FIS-B? I don't see any mention of it on this page. Do you know or something I'm missing? https://www.dynonavionics.com/adsb-dual-band-receiver-472.php
 
kicktireslightfires said:
Many thanks, chemgeek! Do you know if the Dynon displays/indicate when it is and when it is not receiving all ADS-B data?

What about plane-to-plane ADS-B? You said ADS-B doesn't' become available until 1500-2000 AGL, so you wouldn't be able to get ADS-B in traffic until at least 1500 AGL?
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I don't know anything about the Dynon displays. In general, your display devices will always display the latest FIS-B information if they are receiving signals. If signal integrity is interrupted, most devices will annunciate loss of signal or remove information from their displays. METARs and NexRad normally display with timestamps of some sort on display devices.
 
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I've had the chance to compare these side-by-side and next to onboard Wx Radar on the same flight. It was my experience that the XM had much higher resolution but that both had a significant time lag as compared to the onboard Wx Radar. I think the Nexrad display devices are good for deviating around weather but I would not use them to penetrate weather. But that last thought is old news. Since I am not using Nexrad to penetrate weather I don't see a reason to pay for XM. But, if the monthly fee won't change your standard of living then why not, more is better.
 
METARs via ADSB can be quite old, as much as 50 minutes or so. They are continuously being received and mixed in along with radar, lightening, etc. But the originating METAR itself can and often is 30min or more old so the delay is more at the source IMHO.

Traffic is more complex. With ADSB in you can receive it 2 major ways...via the Ground Based Tower transmissions and direct from the other plane.

For the ground based transmission it factors in your location and the proximity of other planes and then sends out traffic information when any two or more planes are within the 3D puck shaped volume. You might not even be in that puck but will still receive it if you are close enough to the tower. You may even see them show up, vanish and reappear depending on the path. Also, for this situation not all planes need ADSB out to show up! In many cases ATC must be injecting non ADSB planes (that have working transponders) into the ADSB rebroadcast feed. But these injected ADSB planes dont show up on sites like FlightAware because flightaware rx stations receive directly from ADSB out transponders.

The other way to receive traffic is directly from another squitting ADSB out unit. Dedicated higher power ADSB out transponders will blast out the ADSB out message at something like 200watts. So you can see them way before they would be in the "puck" and/or when you have no ADSB ground based tower. It seems you can see this traffic way beyond 50 miles! There are also lower power ADSB out units that you can't see quite as far out. I think the Wing and Sky Beacon fall in this category. Not sure about the GDL82.

There are often ADSB towers right on many airports so you can actually pull traffic and weather while idling or taxiing!.

Dont have Sirius XM. I would think for radar alone it would totally beat ADSB for delays and resolution. If it wasnt for the notably higher monthly subscription we'd have it in our plane.
 
You can also call up a map of the locations of ADS-B transmitters if you do a quick web search. In my part of the world, it seems like there aren't many at airports. Rather, they seem to be on top of the hills. The nearest to me is 10-15 miles off the north departure end, so I normally get ADS-B at pattern altitude. I'll have to go look for it on the ground some day. It should be in the middle of the wind farm.

If you read your NOTAMs closely, you will find notices of ADS-B towers out of service. That can affect coverage, although normally my transponder usually reports it can see several towers in cruise.
 
the dynon displays all the info about the weather it is receiving. including how old the data is in minutes.
 
unsafervguy said:
the dynon displays all the info about the weather it is receiving. including how old the data is in minutes.
Click to expand...

Not necessarily how old is the data, rather how long ago it was received by your unit...
 
smv said:
Not necessarily how old is the data, rather how long ago it was received by your unit...
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Yeah I was wondering that too. So if a METAR is like 45min old and ADSB indicates 15 minutes old then its really 1hr old...is that right?
 
Sinistar said:
Yeah I was wondering that too. So if a METAR is like 45min old and ADSB indicates 15 minutes old then its really 1hr old...is that right?
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A METAR should have a timestamp. The timestamp indicates when the METAR was generated.

Where you typically run into problems with "data age" on systems like XM and ADS-B is with NEXRAD and similar products. It can be a fairly significant amount of time from the time the data was captured until it finally reaches your onboard display. Because the images are not really timestamped like a METAR, you have no real way of knowing how long it took to get from radar return to your screen. It could be 20-30 minutes old by the time your system gets the image but your system will tell you it is only 1 min old... 20-30 minutes this time of year can make a huge difference in thunderstorm location.
 
smv said:
Where you typically run into problems with "data age" on systems like XM and ADS-B is with NEXRAD and similar products. It can be a fairly significant amount of time from the time the data was captured until it finally reaches your onboard display.
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Have we gotten a good explanation on the delay yet?
Doesnt data move mmm as electrons, somewhere near the speed of light?
With such huge delays one has to wonder if it is a purposeful or planned inefficiency.
The delays make the info a safety concern, or at least make it of marginal value.
 
Let'sgoflying! said:
Have we gotten a good explanation on the delay yet?
Doesnt data move mmm as electrons, somewhere near the speed of light?
With such huge delays one has to wonder if it is a purposeful or planned inefficiency.
The delays make the info a safety concern, or at least make it of marginal value.
Click to expand...

There is a lot of manual processing and tweaking involved in the process. Human intervention causes delays. As the systems improve and automation gets better we will see (and have seen) improvements.

Using NEXRAD as a "trend" tool works well providing you get enough sequential images, but even the FAA does not consider it a 'forecast' tool.
 
I guess I’d have to witness what the human interaction does in order to understand the 20 minute delay.

The radar picks up returns, a computer converts the data to a format that can be streamed, and off to a server it goes.
Software massages the data for transmission & final consumption, a few seconds later I am looking at what the next hundred miles holds.
So many other more complicated things seem to happen much more quickly in our digital lives these days.
I suppose we have to be patient; its a federal govmnt project.

Might be better if they made the raw data available instantly, let the public purchase systems that will rapidly ‘process & tweak’ it.
 
My understanding from a course I took some time back is that the NEXRAD radar is making numerous sweeps at numerous elevations and the process takes a total of approximately 20 min. After that it is electronically compiled into a composite and disseminated. So, if memory serves, a NEXRAD composite picture will always be a minimum of 20 min. and perhaps 40 min. old. Note: Gray hair is from memory cells dying so I could be off about any or all of this. Good for the big picture terrible for penetrating embedded Wx.
 
That's why I love the stormscope. Those show a real time indication of lightning. Of course, development can always happen once you've penetrated. Almost got caught by that last week. Line of T storms, NEXRAD and stormscope both showed a break in the wall. I thought about it, decided, nah, land and wait 30 minutes instead. Well, that break became a horseshoe, then a doughnut, and then collapsed completely. That would have been a fun ride. Sat it out, waited 2 hours, got a great lightning show.
 
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Arnold said:
My understanding from a course I took some time back is that the NEXRAD radar is making numerous sweeps at numerous elevations and the process takes a total of approximately 20 min. After that it is electronically compiled into a composite and disseminated. So, if memory serves, a NEXRAD composite picture will always be a minimum of 20 min. and perhaps 40 min. old. Note: Gray hair is from memory cells dying so I could be off about any or all of this. Good for the big picture terrible for penetrating embedded Wx.
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This is correct. The radar site collects several 360 degree sweeps at different azimuth angles (the number and arrangement of which depends on weather conditions). This data is then used to create composite reflectivity maps. The data collection takes 5-10 minutes of so depending on the radar mode. FIS-B waits until the full set of sweeps is complete to process data for broadcast to aircraft. XM checks in every 5 minutes and creates running average composite maps with whatever data it has at the time from each elevation. With FIS-B, NEXRAD data should be updated every 10 minutes or so. The data link to your aircraft is really slow, so it could take quite a few minutes to upload it all. At the beginning of a new radar sweep cycle, and before you have received full data being processed from the last cycle, it is conceivable that your currently displayed data could be 15-20 minutes old, depending on sweep modes, data processing time to create the composite maps, and transmission times. As far as I know, this process is completely automated. XM weather should, in theory, be updated a little more frequently. But there is still a significant delay between what the radar sees and what you see on your WX display. I have both XM and FIS-B in my airplane and the XM is definitely less "flaky" and updates more frequently, so I've kept XM for now. But their algorithms are different, so the displays are not always the same.

In-flight NEXRAD is more for strategic, rather than tactical weather avoidance. Still nice to have, though. It's good to know about and give an early wide berth to patches of weather you don't want to be in or close to. Especially when in IMC.
 
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