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Page: of 10

daberti

14 Posts

Posted - 20 août 2006 :  22:38:24  Show Profile  Reply with Quote
quote:
Originally posted by frder

I don't think so. Because the number ranges below 33, and the first SBAS satellite number is 33, and also because in the NMEA sentences there is'nt any information of what the receiver is scanning. If an EGNOS satellite is tracked, even for a second, it appears in the first available line after the GPS satellites and on the satellite map, with azimuth, elevation and signal power data.

francesco



That's what I'm trying to say: there I read satellites above 32.....

EDIT August 22th: starting from yesterday and confirmed today: I got some stable EGNOS mode hooking on sat. 39

Edited by - daberti on 22 août 2006 21:18:15
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zpintar

10 Posts

Posted - 22 sept. 2006 :  07:54:27  Show Profile  Reply with Quote
quote:
Originally posted by lperez

Hello.
I have a FS n560, which FW is GSW3.1.1HTC_3.1.00.07-C23P1.00a.
As I saw previously on the forum, with this fw version I should be able to use DGPS, but I can't.


Anybody knows how to set up SBAS?




I have same problem on my n560. Today I'll try to forcing PRN 126, this is only what I didn't try yet!
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aaronprez

USA
21 Posts

Posted - 06 nov. 2006 :  21:58:41  Show Profile  Reply with Quote
quote:
Originally posted by daberti

quote:
Originally posted by frder
No, the EGNOS satellites are always the last satellite reported in the column/line (since in the GSV sentences they are always reported as the last satellite). The numbers are 33,37,39.
I dont't know what's the meaning of the number in the last line in AFTrack's satellite view that is slightly on the right.

francesco


Such a number is just on the right, last line. I guess it shows the WAAS/EGNOS satellite scanning status, and in fact it scans. But does not manage to get any of them.

Ciao



I think that number is the average signal strength of all satellites that the receiver is currently locked on to. That's why it gets higher when you go to open areas, even higher using an external antenna, and lower when you go inside, and really low when you put your hand over the receiver.

Edited by - aaronprez on 10 nov. 2006 00:19:14
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GTBecker

USA
49 Posts

Posted - 08 nov. 2006 :  22:41:03  Show Profile  Reply with Quote
Please excuse the dupe post.

I just concluded a simultaneous comparison of the SBAS channel function of a new SiRFStarIII chipset in a GlobalSat BT-359W (said to be WAAS-enabled) and a SiRFStarII chipset in an older BU-303 (WAAS-capable but not enabled by default).

From southwest Florida, the new BT-359W recognizes a signal from geostationary PRN 122 (Inmarsat 4F2), but it does not decode the corrections despite an apparently excellent signal. That is the only SBAS signal that this receiver indicates.

Conversely, once enabled the BU-303 gets EGNOS corrections from PRN 120 (Inmarsat 4F2), and WAAS corrections from PRN 122 (3F4), PRN 135 (Galaxy 15) and PRN 138 (Anik F1R). It also points to but can't see PRN 126 and PRN 134.

Oddly, the two receivers think that PRN 122 is a different satellite. The BT-359W points to 4F2 at 53W, while the BU-303 points to 3F4 at 142W. If the BU-303 eventually recognizes 4F2, it would have access to five PSAS sources from here.

Still, of course, the -III outperforms the -II. Why, though, can the two receivers not see the same PSAS sources?


Tom
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gpspassion

93886 Posts

Posted - 08 nov. 2006 :  22:55:10  Show Profile  Visit gpspassion's Homepage  Reply with Quote
What you've found seems to indicate that some internal "tables" in the firmwares are "problematic" and would explain the mixed results, you could try going to www.n2yo.com to see which one's right, based on the better SBAS handling in the SS2 GPS I think we have the answer.

Discounts and Assistance/Réductions et Assistance (Club GpsPasSion) / Où commencer?
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aaronprez

USA
21 Posts

Posted - 08 nov. 2006 :  23:03:36  Show Profile  Reply with Quote
quote:
Originally posted by GTBecker
Oddly, the two receivers think that PRN 122 is a different satellite. The BT-359W points to 4F2 at 53W, while the BU-303 points to 3F4 at 142W. If the BU-303 eventually recognizes 4F2, it would have access to five PSAS sources from here.
I have a Holux 236 GPSlim (Sirfstar III) I have experienced exactly what you are talking about, where it sees PRN 122, but it shows it in the Southeast sky on all the satellite views of all my software, but I darn well know that it is in the Southwest over the Pacific Ocean. I am located in Northwest Indiana. Like you said, it is showing a #35 (PRN 122), but it is showing it being in the location of Inmarsat 4F2. I think something is screwy with Sirfstar III.
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GTBecker

USA
49 Posts

Posted - 08 nov. 2006 :  23:54:26  Show Profile  Reply with Quote
The left window is the BU-303, and the right window is the BT-359W.
http://images.rightime.com/WAAS/SiRF2vs3.GIF

It looks like SiRFStar-IIIs are looking at PRN 121 and calling it PRN 122. The SiRFStar-II can't find a PRN 121.


Tom
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aaronprez

USA
21 Posts

Posted - 09 nov. 2006 :  00:25:55  Show Profile  Reply with Quote
quote:
Originally posted by GTBecker

The left window is the BU-303, and the right window is the BT-359W.
http://images.rightime.com/WAAS/SiRF2vs3.GIF

It looks like SiRFStar-IIIs are looking at PRN 121 and calling it PRN 122. The SiRFStar-II can't find a PRN 121.




I agree. Here is my screenshot:

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aaronprez

USA
21 Posts

Posted - 09 nov. 2006 :  01:20:48  Show Profile  Reply with Quote
quote:
Originally posted by GTBecker

The left window is the BU-303, and the right window is the BT-359W.
http://images.rightime.com/WAAS/SiRF2vs3.GIF

It looks like SiRFStar-IIIs are looking at PRN 121 and calling it PRN 122. The SiRFStar-II can't find a PRN 121.




Using the satellite tracker here http://www.lyngsat.com/tracker/inmar4f2.html
The azimith and elevation angles completely agree that it is the satellite based on when you click on our respective locations in Indiana and Florida. Now that we've identified that this the happening, we just need to figure out why. Since it's not even a WAAS satellite, the receiver tracking it is doing us no good.
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GTBecker

USA
49 Posts

Posted - 09 nov. 2006 :  03:04:08  Show Profile  Reply with Quote
quote:
Originally posted by GTBecker

... It also points to but can't see PRN 126 and PRN 134.



Those two satellites are on the other side of the planet from me, so their existence can only be known via an almanac that the BU-303 collected. Also, AOR-W moved from 53W to 142W earlier this year and kept the PRN 122 designation; its position at 53W was then taken by 4F2, a new satellite that appears to not carry PSAS. So, my guess is that the SiRFStar-III isn't getting the WAAS almanac and is showing old, apparently preloaded, position data for PRN 122.

I admit to being confused about just where PRN 122 was and have tended to try to provide a perfect view of a non-WAAS bird (at 53W) to the BT-359W, unproductively. In the morning I'll find a good view point for 142W, where PRN 122 really is, and try to get a WAAS almanac into it. Maybe then it will be able to find the others that are higher in the sky for me.




Tom
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GTBecker

USA
49 Posts

Posted - 09 nov. 2006 :  14:21:02  Show Profile  Reply with Quote
I am assuming that SiRF (and all that use them) has not released a product that simply does not and cannot work; if they have, they've got a legal problem. But assuming that is not so, perhaps something has put these receivers in a WAAS mode that they cannot escape from.

Here's a guess:

When PRN 122 was moved to 142W, my understanding is that ranging was disabled; that is, the satellite is sending WAAS corrections but is not acting as an stationary GPS position reference.

SiRFStar-IIIs first see the satellite after a cold start but perhaps unnecessarily reject it as a WAAS source because is isn't ranging - but they still get the WAAS almanac from it. PRN 122's WAAS almanac does not yet list the two new WAAS birds, PRN 135 and PRN 138; they are both functioning and sending corrections, but are not yet officially operational - set to Do Not Use for airmen. So, SiRFStar-IIIs don't know about the new WAAS sources but don't look for them, either, since the PRN 122 almanac lacks them. That leaves the receiver with one apparently bad WAAS source that it won't use (but SiRFStar-IIs will).

My proposal is to cold start the receiver and prevent it from seeing PRN122 until it has discovered another WAAS source. I propose we try a cold start and place the receiver in a position that sees the new birds _but which blocks PRN 122 at 143W_. This isn't easy for me since all of them are southwest of me, but PRN 122 is low and the other two are high in the sky. I can use my metal garage door to block the low one, I think.

With the BT-359W, we must either connect Bluetooth to the receiver or power it via USB to make certain it does not auto-power-off before it finds either PRN 135 or PRN 138, and hope it doesn't see PRN 122 first. This might be accelerated by forcing the receiver to look for PRN 135 or PRN 138 after the cold start while blocking PRN 122.

Report later.


Tom
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aaronprez

USA
21 Posts

Posted - 09 nov. 2006 :  20:33:52  Show Profile  Reply with Quote
According to this, PRN 135 (48) is now out of test mode and is operational since 2:00 CST this morning:

http://www.nstb.tc.faa.gov/incoming/New_WAAS_Geo_Status.pdf

New WAAS GEO Status as of 11/9/06
INTELSAT(PanAmSat), Galaxy-15, W133 deg, PRN -135 (48)
PRN-135 was taken out of "Test Mode" and placed in normal mode at 08:00 UTC
on 11/9.
PRN-135 will operate for about the first 6 to 9 months as a data link of correction
and integrity information only. That is, the UDRE will be set to "not monitored".
This will result in it being displayed with a "hollow bar" on some receiver displays.
The ranging control loop for PRN-135 will be running, but the WAAS ground system
will not provide UDREs smaller than Not Monitored until the FAA's verification of
the integrity analyses for the ranging function have been completed as part of the
PRN-138 testing. (Data link only operation allowed the PRN-135 deployment to be
accelerated to compensate for the loss of PRN-122 in the North East)
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aaronprez

USA
21 Posts

Posted - 09 nov. 2006 :  22:46:13  Show Profile  Reply with Quote
I think I have come to a conclusion on why WAAS isn't working on SirfstarIII.

I can't explain why it is misidentifying PRN 122. But what I did was force PRN 135 under "SBAS Control" using Sirfdemo, which made it stop attempting to track that "false PRN 122" satellite, and PRN 135 came up for a split second for me maybe about 3 times in 20 minutes (disappears too fast to get a screenshot), in an area that has a great view of the southwest, and using an external antenna. The reason that it is so hard for the receiver to track it is because the power mask for tracking is set to 28 dBHz, so it will only attempt to track that satellite if the signal for it gets above that, which apparently won't really happen here in northwest Indiana for more than a split second. I think if we were allowed to disable or change the tracking power mask to something lower, it would be able to be tracked. Whether or not we would be able to download the almanac and receive corrections from it would be the next question.

I am not impressed by this limitation of the Sirfstar III, and if I don't get an answer from Holux or maybe even attempt to contact Sirf, this will be my last Sirf product, and I am going to give them bad word of mouth. I think the only way you are going to be able to change the tracking power mask is by a firmware upgrade. I believe the tracking power mask is hard coded in. Evidence is as follows:

Here is from the Sirf Binary reference:



Notice how it says it defaults to 28 dBHz, and then lower down it says "not implemented." I have been able to send Sirf binary to my receiver using Sirfdemo (and be able to change the navigation power mask (which it does only allow to be between 20 and 50) but changing the value of the tracking power mask does not set in the receiver.

I would venture a guess the reason that they don't want the receiver using satellites with signals less than 28 dBHz because of multipath and may make the receiver less accurate. This is bad implementation, and they should have a separate power mask for the WAAS satellites or disable it for WAAS ones, since we just want to use them to get the correction data, and really don't care about ranging from them. But I am no expert, I just play one on TV.

If any experts have any analysis of my analysis, feel free to chime in. Later on I am going to try forcing PRN 138 and see if it will find it at all. I don't think it will, but what the heck. I have a Gilsson antenna being shipped to me, because the external antenna I am using is a cheapy. We'll see if that makes a difference too. I will report any other findings.

Edited by - aaronprez on 10 nov. 2006 01:39:46
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aaronprez

USA
21 Posts

Posted - 09 nov. 2006 :  23:50:41  Show Profile  Reply with Quote
I forced PRN 138, and I was able to see it like I did PRN 135, where it disappears just as fast as it appears. Since this is the one that is highest in the sky to the United States, I don't think a Sirfstar III chipset will ever be able to use WAAS from northwest Indiana on the ground, unless that tracking power mask is able to be set lower or disabled. Maybe the Gilsson antenna that I am getting may help, but I doubt it will be enough to make that signal consistently receive a signal above 28 dBHz. At least today I proved to myself that a satellite can be tracked when it is in test mode using a Sirfstar III.

Here is the definition of the power mask:

"Power Mask
GPS satellites that have a low signal strength are not easily tracked by a GPS receiver
and may result in using signals that are either noisy or have been effected by multipath
or other interference source.
The power mask parameter allows a user to prevent the use of satellites with a low
signal strength being used in the position solution. This will result in a potentially
higher accuracy position. However, as the number of satellites available will be
decreased, the fix density will be decreased."


BTBecker (Tom), can you look in Sirfdemo for on your Sirfstar II receiver, and see what the tracking power mask is set to? Do you have any other conclusions?

Edited by - aaronprez on 10 nov. 2006 01:46:24
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GTBecker

USA
49 Posts

Posted - 10 nov. 2006 :  01:55:55  Show Profile  Reply with Quote
The PowerMask value in the SiRFStar-II is the same, 28dBHz, but it looks like that parameter does not affect the WAAS data channel; no value changed the SBAS processing. Perhaps it would apply to ranging in the -III, though.

You're a step ahead of me if you get to see PRN 135 or 138 at all. I'm still working on it - and waiting for an answer from USGlobal.


Tom


Tom
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