Seeing No D's? (new 60cx)

[+EraSeek]

About 5 minutes ago, 33 & D's.

Was #33 the only SBAS signal you were receiving? Since #33 is an EGNOS bird rather than WAAS the correction data would be based on observations from the European ground stations and wouldn't be the best to use in Pennsylvania.

 

According to gpsinformation.org

"While many receivers claim support for WAAS these days the implementation may not be the same in all receiver designs. For example, receivers using the SiRF chipset will only devote one channel to WAAS reception"

 

All you need is one WAAS sat, but if you can get #33 and #35 but 33 is closer, I wonder if that is why some of are having problems.

[+PDOP's]

Excerpt from IRB Executive Summary

 

"The greatest near-term risk to system availability is the current dependence on only two International Maritime Satellite Organization (INMARSAT) communications-relay satellites (called bent-pipes) for transmission of integrity and ranging corrections. These geosynchronous satellites (GEO) have poor ranging accuracy and vulnerable uplinks....

 

Interesting. I wonder if this anything to do with the high orbital altitude of the geos? Fizzy?

[+fizzymagic]

Excerpt from IRB Executive Summary

 

"The greatest near-term risk to system availability is the current dependence on only two International Maritime Satellite Organization (INMARSAT) communications-relay satellites (called bent-pipes) for transmission of integrity and ranging corrections. These geosynchronous satellites (GEO) have poor ranging accuracy and vulnerable uplinks....

Interesting. I wonder if this anything to do with the high orbital altitude of the geos? Fizzy?

I don't know for certain, but I believe that it is because the GEO WAAS satellites don't have their own atomic clocks onboard, and rely instead on the signal received from the ground for their clock. Thus, any small errors in propagation of that data would appear as clock errors.

 

Reference is here:

The generation of the WAAS ranging signal itself is also interesting. In GPS, the range signal is generated from a set of atomic clocks onboard the GPS satellite. In WAAS, the signal is generated on the ground with WAAS Network Time. The signal is beamed up to the GEO, where a "bent pipe" transponder sends it back down to the service area.

This, by the way, naturally explains why ranging is not available while a WAAS satellite is being moved. In order for the scheme to work, you need to know exactly where the satellite is.

[indygpser]

My StreetPilot c550 has a SiRFstar III receiver. According to Garmin, it can't show any "D" symbols, since SiRF uses the data differently, compared to Garmin, hence there's no knowledge about when to display the "D".

 

What says SiRF is different in the 60CSX?

 

I have seen a couple of requests for those who claim that they are seeing "d"s to post a screenshot indicating such, and not one such post yet. I'm not trying to stir up a hornets nest, but I want to see the screenshot.

[+Wild Thing 73]

I see "d" 's sometimes when 33 is available on my 60cx.

What are "d"s?

[+PDOP's]

I don't know for certain, but I believe that it is because the GEO WAAS satellites don't have their own atomic clocks onboard, and rely instead on the signal received from the ground for their clock. Thus, any small errors in propagation of that data would appear as clock errors.

 

Thanks Fizzy. I'm guessing that although the distance that the signal has to travel up to the geo is constant and could be adjusted for, the signal is subject to the same varying ionospheric delays as regular ranging signals and this is one of the source of the errors.

Edited April 9, 2006 by PDOP's

[+PDOP's]

I see "d" 's sometimes when 33 is available on my 60cx.

What are "d"s?

 

Garmin GPSr's show a "D" in the satellite signal strength bars when receiving WAAS correction signals as shown below.

 

*** Note this is from a 76C not Cx ***

 

[+EraSeek]

I don't know for certain, but I believe that it is because the GEO WAAS satellites don't have their own atomic clocks onboard, and rely instead on the signal received from the ground for their clock. Thus, any small errors in propagation of that data would appear as clock errors.

 

Thanks Fizzy. I'm guessing that although the distance that the signal has to travel up to the geo is constant and could be adjusted for, the signal is subject to the same varying ionospheric delays as regular ranging signals and this is one of the source of the errors.

 

"In addition to correction data the WAAS system places a high degree of importance to system integrity. Each ground station and the master station has independent sources of critical data and can determine if an SV is out of calibration. Bad data can be identified and relayed to the receiver within about 6 seconds. The geosynchronus satellites that retransmit the data can even be used as regular GPS satellites as part of the regular GPS solution since they also relay regular satellite ephemeris data for themselves. This data , like all of the other data, is generated at the master station and can be turned off independent from the regular WAAS corrections if the satellite drifts too far.

[+Wild Thing 73]

I see "d" 's sometimes when 33 is available on my 60cx.

I see them on my black bars, but

What are "d"s?

[+Wild Thing 73]

I see "d" 's sometimes when 33 is available on my 60cx.

What are "d"s?

 

Garmin GPSr's show a "D" in the satellite signal strength bars when receiving WAAS correction signals as shown below.

 

*** Note this is from a 76C not Cx ***

 

Thanks PDOP for the information about the "d"s...I was just out searching for a cache (didn't find) and for the first time noticed the "d"s...I just keep learning > thanks to cachers like you and this & other forum:)

Edited April 9, 2006 by Wild Thing 73

[planewood]

Here's the response I got from Garmin re:Waas and my 60cx.

 

----------------

Thank you for contacting Garmin Product Support.

 

The unit sounds like it is using the differential data, but that the WAAS satellite isn't sending the effemorous data. Once that data resumes it should show the D's. If the Accuracy of the unit is less than 12 feet, it is definitely using the differential data.

 

Please let me know if I can help in any further way, and thanks for choosing Garmin.

 

Warmest Regards,

John R.

-------------------

 

The 60 cx worked great in the woods with 8'-11' stated accuracy and Waas turned off. The oaks up there were just beginning to show opening leaf buds. I will be validating the gathered data this next week, but so far it looks pretty good, considering.

 

I did see 35 as a flashing hollow bar (no d's) from northern OK in the ESE and it had moved down in elevation (closer to the horizon) as compared to here west of Houston.

 

Like I said earlier, I did get D's one day about 4 weeks ago from 35.

 

And, the auto-routing with the standard map that came with the unit did prevent me from missing a few turns while travelling! But, while fiddling with the unit I missed a turn!

[indygpser]

I was getting 8' stated accuracy for a while, now it's varying from 14' to 20'

 

It's my understanding ,that the 60CSx does not have D's and the WAAS sat will show as a hollow bar, just like in your pic. The numbers you stated as EPE are near the stated accuracy.

 

 

Not true, here is a pic I took just today of my 60CSx with the "d's".

 

[+EraSeek]

Interesting. You have the D's, but the only differential sat you have is 33, which is a enos sat. Thus the only corrections you are/should be getting is clock/position corrections because enos sats should not transmit the US ionospheric grid corrections, as far as I know. Guess D's still show with out those corrections, or else show when the enos ionosphere corrections are present but not applied.

[+greengecko]

My 60CSx often shows d's in eleven bars and a hollow bar on 33 with WAAS disabled. I have the Ver. 2.70 software update.

[+drbugs]

I have (had) a 60cx, and live in the upper midwest. Normally I just get a hollow 35 in the SE, with no 'D's. when I was in California last week, after the unit downloaded the almanac for 47, I then saw 35 in the SW, solid bar, with 'D's.

 

Back in the midwest, it's appears in the SE with hollow bar, no 'D's.

[aregrim]

I have just bought a gps 60 cx and I have been able to get a epe of 2mtrs(6 1/2ft), this was with waas turned off. I then turned waas on and got the same epe but the differance was that I got "d's"on all 8 sats. I then turned waas off and lost the "d's).

I was getting 8' stated accuracy for a while, now it's varying from 14' to 20'

 

It's my understanding ,that the 60CSx does not have D's and the WAAS sat will show as a hollow bar, just like in your pic. The numbers you stated as EPE are near the stated accuracy.

 

60CSx Specs state;

 

GPS accuracy:

 

Position: <10 meters, typical (32 feet)

Velocity: .05 meter/sec steady state

DGPS (WAAS) accuracy:

 

Position: <5 meters, typical (16 feet)

Velocity: .05 meter/sec steady state

 

The Manual also states that sometimes the waas signal will degrade the accuracy and in such cases the 60csx will automatically disregard the waas info. (page97)

[+myotis]

I live in IL by St Louis. I have had 3 60CSXs now (I have had to return 2 since Garmin kept telling me it was a hardware problem when it was my custom POIs locking up the maps) and up until I took a trip to WV over the weekend, I was never able to get a WAAS fix. In WV, I was able to get a WAAS fix with no problem. I forget which number I locked onto, but I got the Ds. Now back in IL, I cannot get a WAAS fix.

[-Oz-]

This is because the position of 35 is incorrect. It'll get fixed once they're permanent.

[+hogrod]

This is because the position of 35 is incorrect. It'll get fixed once they're permanent.

 

still seems strange that I can get waas with d's on our legendC, but only ever see #35 for a few seconds then it disappear on our 60cx, this is using both in same location in southern WI. I am still happy with the 60cx even without receiving waas corrections, I have gotten as low as 10ft claimed accuracy without waas.

[indygpser]

My StreetPilot c550 has a SiRFstar III receiver. According to Garmin, it can't show any "D" symbols, since SiRF uses the data differently, compared to Garmin, hence there's no knowledge about when to display the "D".

 

What says SiRF is different in the 60CSX?

 

Not to get off-topic, but how do you like your c550? How is the integrated traffic receiver? How is the bluetooth? I'm thinking of selling my Nuvi 350 and purchasing a c550.

[Hertzog]

This is because the position of 35 is incorrect. It'll get fixed once they're permanent.

In my opinion that should have happened in the last round of updates (2.7/2.5). 35 was in its final position long before these came out, and unless I'm missing something updating 35's position in the firmware should be pretty simple.

[+hogrod]

This is because the position of 35 is incorrect. It'll get fixed once they're permanent.

In my opinion that should have happened in the last round of updates (2.7/2.5). 35 was in its final position long before these came out, and unless I'm missing something updating 35's position in the firmware should be pretty simple.

 

looking into this more tonight, I noticed that when the 60cx sees waas #35, it see it in the south east still. This is very strange considering on your legendC you could almost track the #35 bird every day as it moved from the SE to it's new SW possition, we always see it in the SW now. the longest I have seen the #35 come up on the 60cx sat. searching is about 10seconds, then it gets dropped.

On our legend C we also see a #48 sat. that seems to give us the waas D's, (its shows up to the west of my location in southern WI) we see #48 most of the time.

[Hertzog]

looking into this more tonight, I noticed that when the 60cx sees waas #35, it see it in the south east still.

That's what we mean when we say that the position data for 35 is incorrect. On the SiRF models the basic positions of the WAAS satellites are "hardwired" in. This is a good approach so long as they don't move, but in the case of 35 it has moved considerably. When first turned on the GPSr thinks 35 is still in the SE, so it puts it there on the satellite page, but rejects its signals (probably because the arrival times are wrong for a satellite in the SE). If the GPSr can recieve 47 or one of the other WAAS satellites it believes in, then it will download correct ephemeris data for 35 from that satellite. Once it knows where 35 really is it will also use data from it, but if you turn the GPSr off (or even go to the "use with GPS off" mode) it reverts back to the hardwired data.

 

For people who can only see 35, it would have been nice if they had updated the hardwired data in the last firmware update since 35 has been in its final position for about 2 months now, but for some reason they didn't do the update.

[planewood]

That's what we mean when we say that the position data for 35 is incorrect. On the SiRF models the basic positions of the WAAS satellites are "hardwired" in. This is a good approach so long as they don't move, but in the case of 35 it has moved considerably. When first turned on the GPSr thinks 35 is still in the SE, so it puts it there on the satellite page, but rejects its signals (probably because the arrival times are wrong for a satellite in the SE). If the GPSr can recieve 47 or one of the other WAAS satellites it believes in, then it will download correct ephemeris data for 35 from that satellite. Once it knows where 35 really is it will also use data from it, but if you turn the GPSr off (or even go to the "use with GPS off" mode) it reverts back to the hardwired data.

 

For people who can only see 35, it would have been nice if they had updated the hardwired data in the last firmware update since 35 has been in its final position for about 2 months now, but for some reason they didn't do the update.

 

Somewhere several months ago I read that once 35 got to the proximity of it's final location that they would spend 2 or 3 months 'tweaking' it's final position. Normal operation was not to be started until this tweaking was finished and that was supposed to be sometimes in June or July. I don't think we'll see 35 broadcasting it location data again until full operation is resumed.

[+Red90]

This has all been explained in the past, but anyway. Here is my 60Cx. It will not try to lock on "35" until is has collected the almanac from "47".

 

[Hertzog]

Somewhere several months ago I read that once 35 got to the proximity of it's final location that they would spend 2 or 3 months 'tweaking' it's final position. Normal operation was not to be started until this tweaking was finished and that was supposed to be sometimes in June or July. I don't think we'll see 35 broadcasting it location data again until full operation is resumed.

That could be the reason they haven't updated 35's position yet, but the current position is a lot better than the old position; it would save a lot of people some grief if they had simply used the current position in the latest firmware rather than original position.

[planewood]

Somewhere several months ago I read that once 35 got to the proximity of it's final location that they would spend 2 or 3 months 'tweaking' it's final position. Normal operation was not to be started until this tweaking was finished and that was supposed to be sometimes in June or July. I don't think we'll see 35 broadcasting it location data again until full operation is resumed.

That could be the reason they haven't updated 35's position yet, but the current position is a lot better than the old position; it would save a lot of people some grief if they had simply used the current position in the latest firmware rather than original position.

 

You'd think, wouldn't you!

 

I've wondered why they even put the location in firmware.

[Hertzog]

You'd think, wouldn't you!

 

I've wondered why they even put the location in firmware.

 

That makes sense to me. In a mature WAAS constellation the satellites aren't going to be moving around, so the GPSr immediately has the WAAS locations without the initial "baking" we are used to to find them. Unfortunately, the release of the 60/76 "x" models coincided with major changes in the constellation.