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View Full Version : ADS-B vs. XM


Weasel
06-06-2013, 08:14 PM
It has been several years now since the first ads-b receivers hit the market.

To those of you that have at least 1 year or more flying with XM in an IFR environment and have
converted to ADS-B.

Would you recommend canceling XM and going with ADS-B?

$69 a month sorta steep for weather service. Been paying it for years but only because there was not anything available otherwise.

From the advertisements it looks like the radar is with less detail and you give up several of the XM weather features.

RV8iator
06-06-2013, 08:30 PM
It has been several years now since the first ads-b receivers hit the market.

To those of you that have at least 1 year or more flying with XM in an IFR environment and have
converted to ADS-B.

Would you recommend canceling XM and going with ADS-B?

$69 a month sorta steep for weather service. Been paying it for years but only because there was not anything available otherwise.

From the advertisements it looks like the radar is with less detail and you give up several of the XM weather features.

I used XM for several years and switched to ADSB last year and don't regret it one bit.

Where I fly, mainly east of the Missippi, the ADSB coverage is excellent. The only time I miss XM is on the ground, but I find that with 3G if I really need to see the WX on the ground I can, or check it in the FBO.

There are a couple things that I don't get while airborne that I would like, like winds aloft (WingX doesn't have that feature yet) but once again, I update WX before I leave SOS they are usually pretty current. I get current metals and TAFs and notams and about the oldest ADSB radar reports I see are no more than 5 or 6 minutes old.

I get all the weather and traffic on my EFIS and my iPad and I've gotten used to the difference one the displays. I find that ADSB weather displays a little worse than what's really there, compared to XM and I've adjusted the way I use it accordingly. I still will not fly IMC around convective activity, nor would I with XM. Its jus not timely enough to trust in the clouds around thunderstorms.

I've been mostly happy with the ADSB and really like the extra 60 bucks a month in my pocket.

Kyle Boatright
06-06-2013, 08:33 PM
From the advertisements it looks like the radar is with less detail and you give up several of the XM weather features.

Good synopsis. The other thing is that, depending on location, it may not work if you're <5,000'. That means it won't help you if you're scud running or even at a lot of reasonable VFR altitudes. In TS season when you're down low avoiding storms, ADSB may not offer any assistance.

That said, I recently purchased an ADS-B system. I couldn't stomach XM fees and figure if I'm low enough where ADS-B doesn't work, my cell phone and its weather radar app just might.

Brantel
06-06-2013, 08:34 PM
I don't meet your requirements but I will answer anyway.

FIS-B does not work on the ground in most places unless you are close to a ground station.

The national NEXRAD image is lower resolution than the XM version. The regional image is better than the national image. The regional image sort of stays centered on your position. My opinion is the FIS-B NEXRAD is plenty good enough for the stuff that an RV is made for.

FIS- B has the following if your reciever and display support it:
CONUS NEXRAD
Regional NEXRAD
TFR's
TAF's
PIREP's
NOTAM's
SIGMET's
AIRMET's
METAR's
Winds Aloft

I read somewhere once that they plan to expand services in the future.

I have had my reciever for almost a year. I dumped XM soon after I got it.

Weasel
06-07-2013, 06:49 AM
Thanks for the comments guys! Very useful information.

schristo@mac.com
06-07-2013, 07:32 AM
I have been running XM on a 696 and ADS-B on a SkyView for a while... including two coast to coast trips. There is an enormous part of the west where there is NO coverage with ADS-B yet. With ADS-B the time to populate the initial graphic has significant lag; as much as 15 minutes for a complete local picture and longer to see the whole country. Also, METARS and weather are delivered in small chunks and there is not a certain way to know that the dataset is complete... (missing data on the weather image is obvious but not at all with missing, but available, METAR) this is likely from the nature of delivering a local priority to the dataset incrementally and might be partially from the Dynon implementation but the bottom line is that the XM picture is generally much quicker to the screen and gives a completed METAR shot as soon when delivered.

I am not ready to turn off XM weather (I have the minimum package). If I did not fly long cross country in areas where there is no ADS-B coverage I might drop it but it still holds some attraction. The booth for XM at Sun-N-Fun said that they are working on adding features to the lower cost package to try to stay relevant and competitive with ADS-B... so far no change though.

I would really like to have tops and winds at the lower price point, or implemented with ADS-B.

Brantel
06-07-2013, 08:18 AM
Yep, coverage West of the big river can be a challenge at this time but they are expanding it everyday. They still claim to be on track to cover it all by end of the year.

I typically get the regional FIS-B NEXRAD before I hit pattern altitude.

Here is the typical refresh rates for FIS-B and XM. These can vary depending on the equipment used to RX and display the data...

FIS-B (Data table from a Garmin manual):

http://i43.tinypic.com/4q60ro.png

XM (Taken from an AnywhereMap manual):

NEXRAD 5min
METARS 12min
TAFs 12min
Surface Winds 12min
City Forecast 12min
TFR's 12min
Storm Cells 1.25min
IR SAT 15min
Echo Top's 7.5min
Winds Aloft 12min
Lightning 5min
Surface Conditions 12min
AIRMETs 12min
Turbulance 12min
Icing 12min

miyu1975
06-07-2013, 09:18 AM
recent map of ads b coverage.

http://www.foreflight.com/static/img/stratus/stratus-coverage.png

mburch
06-07-2013, 09:52 AM
I would love to know what's going on that requires so many ground stations in and around Grand Junction, Colorado. :)

mcb

hydroguy2
06-07-2013, 09:58 AM
See that big hole in the middle of the map...yep, the one from Canada extending over most of Montana, Idaho, Utah and wyoming. that's where I do 95% of my flying. :( guess I won't be rushing out to get ADS-B equipment this week.

60av8tor
06-07-2013, 10:02 AM
I would love to know what's going on that requires so many ground stations in and around Grand Junction, Colorado. :)

mcb

Merely a stab in the dark, but terrain would be my guess.

RVbySDI
06-07-2013, 10:46 AM
See that big hole in the middle of the map...yep, the one from Canada extending over most of Montana, Idaho, Utah and wyoming. that's where I do 95% of my flying. :( guess I won't be rushing out to get ADS-B equipment this week.And see how that hole expands South and East down into eastern Colorado, most of Kansas, Oklahoma, Missouri and Arkansas? Well, that is where I do 95% of my flying. I am right there with you. :(

N355DW
06-07-2013, 12:04 PM
I am going to have both in the -7. In other aircraft I've had both drop off line at different times more than once for no reason that I could discern. I like redundancy.

Mile High Relic
06-07-2013, 12:26 PM
And see how that hole expands South and East down into eastern Colorado, most of Kansas, Oklahoma, Missouri and Arkansas? Well, that is where I do 95% of my flying. I am right there with you. :(

Yeah, but there aren't any storm in Oklahoma, are there?

One thing I noticed on my recently acquired 696 w/ XM is that there are coverage gaps in the radar picture. If you zoom out far enough the 696 shows these gaps as a different (purplish?) color. Remote areas for sure, just the sort I occasionally fly over.

What I mean is that there can be a big storm, and it would not show up on XM at all (ADS-B too I assume) because there is no weather radar coverage in that area. If you animated the weather, a storm entering that area would go from green/yellow/red to nothing at the boundary.

Maybe this was obvious to everyone else, but it made me go hmm? This is different than the ADS-B coverage issue.

Anyway, I am keeping XM for now, since the ADS-B coverage once I get out of the Denver area isn't very thorough yet. I'm on the $35/mo plan and I suspend it every winter too, so I pay about $200-$250 a year for it. I do plan on a remote GDL39 in the future, and I may even wire up a GDL39 that I know of that is gathering dust in a hangar nearby.

rocketbob
06-07-2013, 12:56 PM
I don't miss winds aloft or the satellite mosaic, so $35/mo suffices for me and I get the radar while I am warming up. A couple of times this was very valuable weather information. That and the cost of buying an ADS-B receiver, and mounting a device to display it on has been a turnoff for me. $35/mo is not a dealbreaker.

GrayHawk
06-07-2013, 02:26 PM
I would love to know what's going on that requires so many ground stations in and around Grand Junction, Colorado. :)

mcb
They are not around Grand Junction but around the mountain resorts that include Aspen. Read that as the rich & famous!

GH

dmaib
06-07-2013, 04:13 PM
I have been using WSI for five years since that is what worked with the Chelton's I had in the panel. I was very happy with WSI, so was not too happy about saying goodbye to it when I pulled the Chelton's out and installed the GRT Horizon Hxr. I have coupled the Radenna Skyradar D2 dual band ADS-B receiver to the Hxr and upgraded my GTX-330 to ES so I now have full ADS-B in and out. I have not taken any long cross countries yet, but coverage is excellent where I am based in FL. I get weather and traffic on the ground (sometimes even in my hangar!). My impressions so far are pretty positive compared to the WSI. Nexrad updates come every 5 minutes without fail. Sometimes the WSI updates could stretch to 10 or 15 minutes. I am happy to be done with the WSI fees, which are pretty much the same as XM, and with the continuing rapid roll out of ADS-B ground stations, I think it was the right move for me. As an aside, I still get the TIS-B traffic on my 430W in addition to the ADS-B traffic on the Hxr display. I notice that occasionally the TIS-B shows traffic that the ADS-B does not show, and vice versa.
Bottom line, I am pleased with the ADS-B, glad to have the new Hxr in the panel, still miss the WSI at times, but don't miss the $$ going out for it.

Brantel
06-07-2013, 04:22 PM
As an aside, I still get the TIS-B traffic on my 430W in addition to the ADS-B traffic on the Hxr display. I notice that occasionally the TIS-B shows traffic that the ADS-B does not show, and vice versa.


Just a slight clarification for those that may read this later...

TIS or TIS-A is the original Traffic Information Service that was available at some terminal areas when you had a Mode-S xponder. Most if not all of the TIS-A systems are scheduled to be or already have been decommissioned.

TIS-B is the Traffic Information Service - Broadcast that is part of the ADS-B system.

The two systems are very different with different strengths and weaknesses so it likely that you may see different traffic when comparing em side by side. Tons of variables come into play to create those differences.

The 430W cannot display TIS-B from a GTX330ES, but it can display TIS-A.

dmaib
06-07-2013, 04:38 PM
Just a slight clarification for those that may read this later...

TIS or TIS-A is the original Traffic Information Service that was available at some terminal areas when you had a Mode-S xponder. Most if not all of the TIS-A systems are scheduled to be or already have been decommissioned.

TIS-B is the Traffic Information Service - Broadcast that is part of the ADS-B system.

The two systems are very different with different strengths and weaknesses so it likely that you may see different traffic when comparing em side by side. Tons of variables come into play to create those differences.

The 430W cannot display TIS-B from a GTX330ES, but it can display TIS-A.

Sorry, I had it backwards.

Brantel
06-07-2013, 05:04 PM
Sorry, I had it backwards.

No worries, it is a very confusing subject. Hard for all of us to keep straight.