Are You Smarter Than a Garmin Engineer?

[+Atlas Cached]

OK, I have been having an ongoing conversation with some people at Garmin about an issue I am having with my eTrex 30x, and I have not been able to get anywhere with them, so I am hoping someone here, Smarter Than a Garmin Engineer, can explain something to me.

 

My eTrex 30x (3.00) Satellite page is doing some things I can not reconcile.

 

First, the eTrex 30x tracks all visible GLONASS satellites correctly, and provides an accurate enough position, but it identified the GLONASS satellites with the wrong NMEA ID numbers. It uses NMEA ID that are correct for GLONASS, but they are not the correct numbers for the visible satellites. In fact, I have been doing some testing, and compared the eTrex 30x to many other Garmin GPSr that also receive GLONASS satellite signals, as well as multiple tablets, phones, and satellite tracking web pages. They all agree with each other except for the eTrex 30x, which always misidentifies the GLONASS satellite ID numbers.

 

Second, the eTrex 30x, and only the eTrex 30x indicate it is receiving Differential Correction Data (SBAS) for the GLONASS satellites. I have been in contact with various PR people at the EGNOS HQ in Europe and the FAA WAAS HQ in the US, and the answers I am getting is that nobody calculates or otherwise makes available SBAS data for GLONASS satellites. EGNOS is scheduled to begin doing so in 2025 when their newest generation of satellites are all put into orbit, but not until then. How in the world does the eTrex 30x think it is receiving augmented data for GLONASS satellites if nobody is transmitting it? Space Aliens? No other GPSr suggests this information is available, only the eTrex 30x

 

Finally, I am in the USA, so I have two or three WAAS satellites available to me for SBAS data, and they are all due south of me, in the sky about 45° above the horizon (over the equator), a little West or East, but primarily south of my location. Yet, for some reason, the eTrex 30x indicates that WAAS satellite 44 is due NORTH of my location and nearly at the horizon, which is just completely wrong.

 

The following images demonstrate these issues clearly:

 

 

Is there an engineer in the house? Can someone please tell me why my eTrex 30x is doing what it is doing? Does anyone else have an eTrex 30x that is exhibiting similar behavior?

 

Is anyone here smarter than a Garmin engineer?

 

 

Edited August 3, 2019 by Atlas Cached

[+Mineral2]

It's this affecting how your GPS displays your position?

[+arisoft]

2 hours ago, Atlas Cached said:

Can someone please tell me why my eTrex 30x is doing what it is doing?

 

The device behaves according to the program stored on the device.

 

2 hours ago, Atlas Cached said:

Is anyone here smarter than a Garmin engineer?

 

Did the Garmin engineer give you a different answer?

 

Answering your question more precisely requires access to the source code of the device.

[capt caper]

Probably wasn't an real engineer. I doubt they would talk to someone in the users field unless it was an emergency of sort.

[+RecipeForDisaster]

Garmin has been unable to solve any of the issues with my 66s ("search near" not working, hard crashing when deviating from a route, losing data to the point of not seeing the SD card after a crash...) , so if someone is smarter and more helpful than who they have "troubleshooting" with me... I'd appreciate it.

[+kunarion]

9 hours ago, Atlas Cached said:

Is there an engineer in the house? Can someone please tell me why my eTrex 30x is doing what it is doing?

 

I've never compared satellite ID numbers across multiple devices, nor have I seen anything that mentions how navigational devices manage the IDs internally.  Have you tried to refresh the catalog on the Etrex?

 

I guess you have the question well handled.  But for my own edification, I did a leetle search of what numbers which satellites are, besides just what Wikipedia shows.  And it sent me directly down a rabbit hole.  But here are a couple of interesting threads, mostly just questions themselves:

 

https://gis.stackexchange.com/questions/65412/is-there-an-industry-standard-official-mapping-of-glonass-satellites-to-prn-va

 

https://stackoverflow.com/questions/17554320/glonass-satellites-are-supported-or-not

 

https://www.gps-forums.com/threads/glonass-id-slots-and-freq-channels.43930/

 

 

[+Atlas Cached]

9 minutes ago, kunarion said:

I've never compared satellite ID numbers across multiple devices, nor have I seen anything that mentions how navigational devices manage the IDs internally.  Have you tried to refresh the catalog on the Etrex?

 

I guess you have the question well handled.  But for my own edification, I did a leetle search of what numbers which satellites are, besides just what Wikipedia shows.  And it sent me directly down a rabbit hole.  But here are a couple of interesting threads, mostly just questions themselves:

 

Yes, my eTrex 30x has been allowed to set in plain view of the sky for many hours uninterrupted to make sure it had ample time to download all current satellite data. This was one of the first things I did when the anomaly was first noticed.

 

I have also done a lot of research on how the Satellites are Identified on Garmin GPSr as well as other platforms, and everyone largely uses the NMEA standard. If you navigate to GPSrChive > eTrex x0x > Specifications and select GLONASS in the 'GPS Network' line, you can see the current live GLONASS constellation as well as track individual GLONASS satellites in real time. There are many more satellite tracking webpages and iOS/Android apps available, and they all use the same NMEA IDs, which for GLONASS is the 'SV Slot Number + 64'. There are additional links on that GLONASS page to information about NMEA ID as well as a complete list of all current satellites.

 

My eTrex 30x misidentifies the entire GLONASS constellation, which I believe is the result of some misplaced code in the firmware.

 

Hopefully another user with an eTrex x0x will test theirs and respond here!

[+Atlas Cached]

9 hours ago, Mineral2 said:

It's this affecting how your GPS displays your position?

 

Didn't read the entire post, huh?

[+Atlas Cached]

7 hours ago, arisoft said:

The device behaves according to the program stored on the device.

 

Did the Garmin engineer give you a different answer?

 

Answering your question more precisely requires access to the source code of the device.

 

Exactly.

 

I was given a 'Canned Answer' that does not explain the behavior.

 

Yes, that would be helpful, but not likely!

[+kunarion]

1 minute ago, Atlas Cached said:

GLONASS is the 'SV Slot Number + 64'.

 

I was expecting to see something in your satellite screen like "PRN -2", where all discrepancies were calculated the same ("subtract 2" or whatever).  But I don't see a pattern.  Weird.

 

But I did read an article about how GLONASS sent incorrect positioning data for a time in 2014.  So who knows.  Maybe your Etrex is the one thing that has the accurate IDs.

[+Atlas Cached]

Just now, kunarion said:

 

I was expecting to see something in your satellite screen like "PRN -2", where all discrepancies were calculated the same ("subtract 2" or whatever).  But I don't see a pattern.  Weird.

 

But I did read an article about how GLONASS sent incorrect positioning data for a time in 2014.  So who knows.  Maybe your Etrex is the one thing that has the accurate IDs.

 

So then all other GPSr and tracking webpages and iOS /Android tracking apps (and even the GLONASS Homepage from Russia) are wrong and just this one little eTrex 30x is correct?

 

Hardly plausible.

[Geoticca]

Did you crosscheck with this site?

https://qzss.go.jp/en/technical/index.html

 

[_Art_]

That might make some sense if you logged the serial output with a serial terminal, and got the screenshot as well.

The order of the sentences might reveal something. It could even reveal that the error is in the NMEA sentences, and the GPS unit software is the problem.

I haven’t done this, but expect that devices with USB (and no real serial port) act like their own serial port with the Garmin driver installed in Windows,

\and could be logged with something like Hyperterminal if the serial port was enabled in the GPS device setup menu.

 

Edited August 3, 2019 by _Art_

[+dprovan]

38 minutes ago, Atlas Cached said:

10 hours ago, Mineral2 said:

It's this affecting how your GPS displays your position?

 

Didn't read the entire post, huh?

Why do you always have to be so snarky? A simple "yes" or "no" would have been so much easier for you to post, even if you can't help yourself and say "...as I said". But the fact is, I have read the OP, several times, and if you said whether this is a problem or a curiosity, I don't see it. So if you insist on maligning people like Mineral2 and me who don't understand what the ultimate effect of this anomaly is, at least have the decency of really rubbing it in by explaining why the answer to Mineral2's question was so obvious that you shouldn't be bothered to answer it. In engineering terms, this is a very interesting question because it would suggest whether this is a fundamental problem with satellite handling or just a superficial problem in the code reporting the information that's puzzling you.

 

As a software engineer, without an answer to this question, my guess is that it's just a bug of the second type: some informational fields in some data structure not being initialized correctly for reasons having nothing to do with satellites, and then being reported as gospel, or a data structure being properly initialized, but then reported by code that doesn't understand the structure as well as it thinks it does.

[+Atlas Cached]

2 hours ago, Geoticca said:

Did you crosscheck with this site?

https://qzss.go.jp/en/technical/index.html

 

 

I had not seen that particular website before, so thank you for the link!

 

Non the less, I cross checked with multiple other GPS receivers and the GLONASS website itself. The eTrex 30x does not agree with any of them.

[+Atlas Cached]

1 hour ago, _Art_ said:

That might make some sense if you logged the serial output with a serial terminal, and got the screenshot as well.

The order of the sentences might reveal something. It could even reveal that the error is in the NMEA sentences, and the GPS unit software is the problem.

I haven’t done this, but expect that devices with USB (and no real serial port) act like their own serial port with the Garmin driver installed in Windows,

\and could be logged with something like Hyperterminal if the serial port was enabled in the GPS device setup menu.

 

 

Do you know of any other NMEA logging software titles?

 

I am not certain I can even access that data from the eTrex 30x, as the only two interface options available are "Mass Storage Mode" or "Garmin Mode'.

 

Edited August 3, 2019 by Atlas Cached

[+arisoft]

2 minutes ago, Atlas Cached said:

Do you know of any other NMEA logging software titles?

 

If you can use the device as an external USB GPSr then you can log NMEA from the serial port allocated for this function.

Your device may not be supported  http://forums.gpsreview.net/discussion/31340/etrex-30x-and-nmea-output

 

[+Atlas Cached]

No NMEA output for eTrex x0x..... 8^(

[+Mineral2]

6 hours ago, Atlas Cached said:

 

Didn't read the entire post, huh?

I did read your post. There's no mention of whether this "issue" is causing a problem with the location calculation. As I look at the screen shots you included, it doesn't appear to be doing so. But then, you only left the full degrees in the images. 

My point was this: If it's not affecting the location calculation of the GPS receiver, then why care how it is identifying satellites?

[_Art_]

It looks like it won’t give serial data

I suspect when they updated to a multi-service GPS module they didn’t fix the parsing for it properly, but if only we had the source code.

[+colleda]

In your OP you have said " my " Etrex 30x. Have you compared or tried other Etrex 30xs? Perhaps it's just yours that has a bug and therefore not being indicative of all Etrex 30xs

[+Atlas Cached]

2 hours ago, colleda said:

In your OP you have said " my " Etrex 30x. Have you compared or tried other Etrex 30xs? Perhaps it's just yours that has a bug and therefore not being indicative of all Etrex 30xs

 

Unlikely. 

 

My eTrex 30x, 20x, and 32x all exhibit identical behavior.

[+MartyBartfast]

2 hours ago, Atlas Cached said:

 

Unlikely. 

 

My eTrex 30x, 20x, and 32x all exhibit identical behavior. 

 

That contradicts what you said in the OP:
 

On 8/3/2019 at 6:02 AM, Atlas Cached said:

In fact, I have been doing some testing, and compared the eTrex 30x to many other Garmin GPSr that also receive GLONASS satellite signals, as well as multiple tablets, phones, and satellite tracking web pages. They all agree with each other except for the eTrex 30x, which always misidentifies the GLONASS satellite ID numbers. 

 

Anyway, the only way anyone will be able to answer this is to see the code, and that means someone from Garmin. Given that this doesn't functionally affect the operation of the device(s) I expect it would come low on Garmin's priority list. Your complaint/query might have made it onto their bug list and might be fixed in a forthcoming firmware update  (are you on the latest firmware?),  but it's they might not want to publish details of the issue.

 

 

[+Red90]

Here is my test.

 

August 4, 2019 06:47 mountain time.  N51 W114.

Edited August 4, 2019 by Red90

[+Atlas Cached]

Thank you Red90!

[+Red90]

It seems the numbering is just different on the Glonass satellites.  Positions look the same.

 

And, yes, it is showing ALL WAAS satellites at the northern horizon.  I've rebooted and connected to a few and they all show center, top of the screen.

 

I get Ds on some Glonass IDs.

Edited August 4, 2019 by Red90

[+kunarion]

I found info on the numbering standard, and I also looked at a couple of my devices that can use GLONASS.  A lot of this has already been covered in this thread, so these results are not anything earth-shattering.

 

https://gpsd.gitlab.io/gpsd/NMEA.html

"GLONASS satellite numbers come in two flavors. If a sentence has a GL talker ID, expect the skyviews to be GLONASS-only and in the range 1-32; you must add 64 to get a globally-unique NMEA ID. If the sentence has a GN talker ID, the device emits a multi-constellation skyview with GLONASS IDs aleady in the 65-96 range."

 

Using the App "GPS Test", my HTC U11 Android phone shows the GLONASS "slot numbers" 1 thru 24.  My Garmin Oregon 750t shows those same satellites and adds 64. I looked at some satellite mapping web sites, and they show the Cosmos Satellite Number (4-digit numbers) or PRN numbers, and never a number in the 65-96 range.  I was hoping to find an online sky map for comparison, but it looks like I'd have to do some number conversions.

 

GPS Test shows the map with track up, and I filtered the map to show only GLONASS satellites.  The Oregon 750t shows the sky map with north up (plus I didn't filter out GPS satellites).  I rotated the GPS Test's screen to compare maps.  I can add 64 to each satellite in GPS Test, and each corresponds to the satellite shown on the Oregon.  The numbers seem fine on mine.  The displayed numbers seem to be based on internal calculations.

 

As for position information or correction data or whatever, I have no idea.  Garmin says that the device uses GPS to obtain coordinates, but everywhere Garmin mentions GLONASS it merely says that the position fix may be faster if GLONASS is turned on.  It's hard to tell if they are saying that any Garmin uses GLONASS to obtain the actual coordinates.  I mean, devices may do that, but Garmin's official wording seems vague on that topic.

 

 

 

 

Edited August 4, 2019 by kunarion

[+Atlas Cached]

36 minutes ago, Red90 said:

It seems the numbering is just different on the Glonass satellites.  Positions look the same.

 

And, yes, it is showing ALL WAAS satellites at the northern horizon.  I've rebooted and connected to a few and they all show center, top of the screen.

 

I get Ds on some Glonass IDs.

 

Thank you for confirming.

 

That is exactly what I am seeing, and is of course completely wrong.

 

Maybe you can contact Garmin and report the issue also?

 

 

[+Atlas Cached]

13 hours ago, kunarion said:

"GLONASS satellite numbers come in two flavors. If a sentence has a GL talker ID, expect the skyviews to be GLONASS-only and in the range 1-32; you must add 64 to get a globally-unique NMEA ID. If the sentence has a GN talker ID, the device emits a multi-constellation skyview with GLONASS IDs aleady in the 65-96 range."

 

Using the App "GPS Test", my HTC U11 Android phone shows the GLONASS "slot numbers" 1 thru 24.  My Garmin Oregon 750t shows those same satellites and adds 64. I looked at some satellite mapping web sites, and they show the Cosmos Satellite Number (4-digit numbers) or PRN numbers, and never a number in the 65-96 range.  I was hoping to find an online sky map for comparison, but it looks like I'd have to do some number conversions.

 

GLONASS has nearly 100 satellites, some very old, some new, some in testing... But the GLONASS satellite positioning system only ever uses 24 at any one time, and those 24 satellites are positioned into specific 'slots' in the constellation, numbered 1 through 24. Since US GPS already uses NMEA = PRN, the GLONASS slot numbers are already in use. To create unique NMEA ID, the GLONASS slot number is added to the number 64, giving NMEA ID of 65-88. There are a few numbers past 88 reserved for future expansion, but they are not used right now.

 

No website should be showing PRN numbers for GLONASS as they do not use PRN to ID satellites like US GPS and EU GALILEO.

 

Checking a number of Satellite tracking websites for real time GLONASS satellite ID compared to the eTrex x0x and x2x (and apparently the Astro 900) reveals that the internal index for these units has an errors identifying the satellites correctly. They are using them successfully (it appears), just not identifying them properly.

 

The link provided in an earlier post for the GPSrChive GLONASS page displays the real time GLONASS constellation status directly from the Russian Federation tracking service.

 

Edited August 5, 2019 by Atlas Cached

[+Atlas Cached]

7 hours ago, MartyBartfast said:

That contradicts what you said in the OP:

 

How so? Those GPSr were not even mentioned in the OP.

 

7 hours ago, MartyBartfast said:

Anyway, the only way anyone will be able to answer this is to see the code, and that means someone from Garmin. Given that this doesn't functionally affect the operation of the device(s) I expect it would come low on Garmin's priority list. Your complaint/query might have made it onto their bug list and might be fixed in a forthcoming firmware update  (are you on the latest firmware?),  but it's they might not want to publish details of the issue.

 

I think a few of us doing some of our own testing and using deductive reasoning may be able to come to a better understanding of what is happening, even without seeing any source code.

 

Yes, as stated in the OP, my eTrex 30x is using the latest firmware.

 

Edited August 4, 2019 by Atlas Cached

[+Atlas Cached]

18 hours ago, Mineral2 said:

I did read your post. There's no mention of whether this "issue" is causing a problem with the location calculation.

 

Read the 4th line again, please.

 

18 hours ago, Mineral2 said:

As I look at the screen shots you included, it doesn't appear to be doing so. But then, you only left the full degrees in the images. 

 

The coordinates shown are more than adequate for this discussion.

 

18 hours ago, Mineral2 said:

My point was this: If it's not affecting the location calculation of the GPS receiver, then why care how it is identifying satellites?

 

Not everyone uses the GPSr for the same purposes. I like to use mine to track satellites, so correct ID's are essential.

[+Mineral2]

8 minutes ago, kunarion said:

As for position information or correction data or whatever, I have no idea.  Garmin says that the device uses GPS to obtain coordinates, but everywhere Garmin mentions GLONASS it merely says that the position fix may be faster if GLONASS is turned on.  It's hard to tell if they are saying that any Garmin uses GLONASS to obtain the actual coordinates.  I mean, devices may do that, but Garmin's official wording seems vague on that topic.

I'm pretty sure that it uses the GLONASS satellites to obtain coordinates, based on the fact that: When GLONASS is turned on, my GPS error estimate is smaller than with GPS alone (more satellites = larger sample size = smaller standard error), and because the GLONASS satellites must not be calibrated the same as the GPS satellites, I often experience different coordinates with GLONASS on and off. That difference is small enough that for wilderness navigation, it's not an issue, but large enough that for Geocaching, it can throw off my search.

[+kunarion]

15 minutes ago, Mineral2 said:

I'm pretty sure that it uses the GLONASS satellites to obtain coordinates, based on the fact that: When GLONASS is turned on, my GPS error estimate is smaller than with GPS alone (more satellites = larger sample size = smaller standard error), and because the GLONASS satellites must not be calibrated the same as the GPS satellites, I often experience different coordinates with GLONASS on and off. That difference is small enough that for wilderness navigation, it's not an issue, but large enough that for Geocaching, it can throw off my search.

 

Garmin is not clear at all on that.

 

I sometimes wonder if more calculations create more chaos in the result, at least where the extra processor work is poorly handled.  On my Oregon 750, I've been caching with WAAS shut off, and no GLONASS either (same with the 650 before that).  I haven't seen any difference as it applies to cache-locating.  Sure, the device reports its amazing new capability once more satellites are added.  At best, the now "more accurate spot" merely makes me confident to search in... the wrong spot.

[+MartyBartfast]

44 minutes ago, Atlas Cached said:

How so? Those GPSr were not even mentioned in the OP.

In your OP you said:

 

On 8/3/2019 at 6:02 AM, Atlas Cached said:

I have been doing some testing, and compared the eTrex 30x to many other Garmin GPSr that also receive GLONASS satellite signals,

I think it's reasonable (in the absence of any clarification)  to  assume  that the set  "many other Garmin GPSr" would have included your 20x and 32x,  or are you now saying that when you did the first set of tests on "many other Garmin GPSr" you didn't bother testing your 20x & 32x?

 

 

 

 

2 hours ago, Atlas Cached said:

Yes, as stated in the OP, my eTrex 30x is using the latest firmware.

Well it's not exactly clearly stated in the OP is it? I assume you're referring to this line:
 

On 8/3/2019 at 6:02 AM, Atlas Cached said:

My eTrex 30x (3.00)

It's not exactly obvious that (3.00) is the firmware rev, and I certainly wouldn't know whether 3.00 is the latest rev for that device.

 

 

 

2 hours ago, Atlas Cached said:

I think a few of us doing some of our own testing and using deductive reasoning may be able to come to a better understanding of what is happening, even without seeing any source code.

I don't think you're likely to get anything other than assumptions and speculation, neither of which is going to give you the real answer.

 

 

[+Atlas Cached]

46 minutes ago, MartyBartfast said:

In your OP you said:

 

I think it's reasonable (in the absence of any clarification)  to  assume  that the set  "many other Garmin GPSr" would have included your 20x and 32x,  or are you now saying that when you did the first set of tests on "many other Garmin GPSr" you didn't bother testing your 20x & 32x?

 

The Image included in the same post makes it clear which models the 'other Garmin GPSr' in that test were.

 

You know what they say, "A picture is worth a thousand words."

 

'Reading comprehension' and 'context' are both required here.

 

46 minutes ago, MartyBartfast said:

Quote

Yes, as stated in the OP, my eTrex 30x is using the latest firmware.

 

Well it's not exactly clearly stated in the OP is it? I assume you're referring to this line:

 

Quote

My eTrex 30x (3.00)

 

It's not exactly obvious that (3.00) is the firmware rev, and I certainly wouldn't know whether 3.00 is the latest rev for that device.

 

More Semantics.

 

46 minutes ago, MartyBartfast said:

I don't think you're likely to get anything other than assumptions and speculation, neither of which is going to give you the real answer.

 

We already have additional confirmation others are seeing the same behavior on their eTrex x0x models as well as other Garmin GPSr models I did not have to test, so we are in fact learning more already.

 

Thank you for your support!

 

[+arisoft]

On 8/3/2019 at 8:02 AM, Atlas Cached said:

Second, the eTrex 30x, and only the eTrex 30x indicate it is receiving Differential Correction Data (SBAS) for the GLONASS satellites. I have been in contact with various PR people at the EGNOS HQ in Europe and the FAA WAAS HQ in the US, and the answers I am getting is that nobody calculates or otherwise makes available SBAS data for GLONASS satellites.

 

This is not totally impossible because the correction data contains ionospheric delay information which, in theory, could be used for other satellite systems using the same frequency. That is hardly the case.

[+MartyBartfast]

1 hour ago, Atlas Cached said:

The Image included in the same post makes it clear which models the 'other Garmin GPSr' in that test were.

 

You know what they say, "A picture is worth a thousand words."

 

'Reading comprehension' and 'context' are both required here.

 

 

So why did you say in the OP

 

On 8/3/2019 at 6:02 AM, Atlas Cached said:

They all agree with each other except for the eTrex 30x,

 

When the fact is several of your devices were also showing the same anomaly as the 30x.

 

Not sure about "Reading comprehension" but you need to be more concise and accurate about what you're posting.

 

Anyway I'm done with this, bye.

[+Atlas Cached]

43 minutes ago, MartyBartfast said:

 

So why did you say in the OP

 

  On 8/2/2019 at 10:02 PM, Atlas Cachedsaid:

They all agree with each other except for the eTrex 30x,

 

When the fact is several of your devices were also showing the same anomaly as the 30x.

 

Not sure about "Reading comprehension" but you need to be more concise and accurate about what you're posting.

 

Anyway I'm done with this, bye.

 

This is where reading comprehension comes into play....

 

None of the other GPSr in that test were exhibiting the same behavior as the eTrex 30x, which is exactly what I stated. Could not be much more concise than I was.

 

Having re-read all your posts in this thread, it is apparent you have nothing on topic or constructive to offer, and appear to only be interested in arguing with someone, which leads me to wonder why you posted here in the first place.

 

Thank you all the same.

 

 

 

 

[+kunarion]

On ‎8‎/‎3‎/‎2019 at 11:47 AM, Geoticca said:

Did you crosscheck with this site?

https://qzss.go.jp/en/technical/index.html

 

 

Is there a conversion chart?  That site is tracking "700-799".  There are 24 GLONASS satellites in use, with some spares.  Other sites list slot numbers "1-24", or "65-88" (adding "64" to the slot number).  How do I match the satellites to their "slot number"?

 

EDIT:  I found a decent chart here.  Looks like although there are more than 24 GLONASS satellites, even the spares are given slots in the range of 1 to 24 (they get duplicate numbers).  If so, the Etrex display of ID numbers 90-92 is not possible.

 

Edited August 4, 2019 by kunarion

[+kunarion]

On ‎8‎/‎3‎/‎2019 at 11:25 AM, Atlas Cached said:

My eTrex 30x misidentifies the entire GLONASS constellation, which I believe is the result of some misplaced code in the firmware.

 

From your screen shot, it almost looks like several numbers are transposed on screen.  Plus, satellites 90-92 should not even be shown here, nevermind providing "correction data".

 

It's got to be only a display glitch.  The satellite position and calculation are correct.  The displayed numbers are scrambled.  Anyway, that Garmin engineer you were asking about, would take one look at "GLONASS #92", for example, and know it's a bug to work on.

 

 

Edited August 4, 2019 by kunarion

[+GeoTrekker26]

1 hour ago, kunarion said:

 

From your screen shot, it almost looks like several numbers are transposed on screen.  Plus, satellites 90-92 should not even be shown here, nevermind providing "correction data".

 

It's got to be only a display glitch.  The satellite position and calculation are correct.  The displayed numbers are scrambled.  Anyway, that Garmin engineer you were asking about, would take one look at "GLONASS #92", for example, and know it's a bug to work on.

 

 

Isn't 92 partially hidden behind 28?  I also clearly see 90 and 91 in both the bar chart and compass display.  I'm obviously missing something here, so any clarification is appreciated.

[+kunarion]

51 minutes ago, GeoTrekker26 said:

Isn't 92 partially hidden behind 28?  I also clearly see 90 and 91 in both the bar chart and compass display.  I'm obviously missing something here, so any clarification is appreciated.

 

Yeah, "92" was just an example on that screen and its icon is probably behind 28's icon (28 here is a GPS satellite).  The engineer could instead look at 90 or 91 and know they aren't real IDs. Those are in full view. From what I've found so far (and sure, it can get kinda vague), no GLONASS ID above 88 should be listed, while 90, 91, and 92 aren't a real thing.  There are 24 GLONASS slots 1 thru 24, and when you add 64 (the number to add), on a Garmin handheld the highest possible displayed GLONASS ID is "88".  The Etrex 30 is doing something extra funky.

 

 

 

Edited August 5, 2019 by kunarion

[Geoticca]

For users with an iphone, this app also might be very helpful

https://apps.apple.com/at/app/gps-plan/id623849032

 

[+Atlas Cached]

On 8/4/2019 at 4:16 PM, kunarion said:

 

Is there a conversion chart?  That site is tracking "700-799".  There are 24 GLONASS satellites in use, with some spares.  Other sites list slot numbers "1-24", or "65-88" (adding "64" to the slot number).  How do I match the satellites to their "slot number"?

 

 

All of that information is available at GPSrChive > GNSS.

[Geoticca]

1 hour ago, Atlas Cached said:

 

All of that information is available at GPSrChive > GNSS.

Can you link it exactly - could not find any GNSS on this site

thank you

[+kunarion]

12 minutes ago, Geoticca said:

Can you link it exactly - could not find any GNSS on this site

thank you

 

The CPSrChive GLONASS list is at the very bottom of this page in the "Satellite Tracking" chart.

 

Here's the one I found that shows GLONASS spares and the status of more satellites. It may be handy when that engineer shows up and tries to explain IDs "90, 91, and 92".  You can check his work. 

 

 

Edited August 6, 2019 by kunarion

[+Team CowboyPapa]

WRT to the thread title:  Depends on how many there are.  If there are 100 or more Garmin engineers, yes, I am smarter than at least one!

Edited August 7, 2019 by Team CowboyPapa

[+Atlas Cached]

1 hour ago, Geoticca said:

Can you link it exactly - could not find any GNSS on this site

thank you

 

Using Chrome? You might need to refresh your browser as it is likely showing you an old version of the website.

[+stefanwilkens]

In the Netherlands, I just checked for you. My phone shows GLONASS satellites between 08 and 24, meaning 72 up to 88. My eTrex shows GLONASS up to 92.

 

Could it be that these are GLONASS-M units (that range from 21 to 92?) 

 

https://en.wikipedia.org/wiki/GLONASS

 

Quote

Glonass-M includes 31 satellites ranging from satellite index 21 - 92 and with 4 spare active satellites.

 

Edited August 9, 2019 by stefanwilkens

[+stefanwilkens]

 

On 8/3/2019 at 5:47 PM, Geoticca said:

Did you crosscheck with this site?

https://qzss.go.jp/en/technical/index.html

 

 

I did, the positions seem to correlate.

 

The website:

 

My eTrex 20x:

 

The positions of the GLONASS units seems to overlap well:

 

This tells me that #745 is GLONASS #91 according to my eTrex 20x. #91 is a satelite ID in the GLONASS-M range, according to the wikipedia link I shared before.

 

Could it be that they use a different numbering scheme for GLONASS compared to GPS?

 

The positions seem to be accurate though.

Edited August 9, 2019 by stefanwilkens