Vista HCx WAAS bugs?

[brian.r.hamilton]

When I first power-up my Garmin eTrex Vista HCx, it displays satellite 49 (PRN 136 I assume) when WAAS is enabled. After a minute or so, it shows a full strength signal with solid coloring for 49 & "D"s for all the other non-WAAS satellites, but never a "D" for 49 itself. It never picks up any other WAAS satellites & won't use the last channel of the receiver.

 

If I bring the GPSr indoors, 49 is lost & 13 takes it's place. 13 remains hollow but the "D"s are still displayed on all other available satellites for longer than 2 minutes (as long as I was in the house - probably at least 10 minutes). If I carry it back outside, 13 won't go away but shows full strength although it remains hollow & the 12th channel remains unused.

 

Next, if I disable WAAS, the "D"s disappear but the GPSr still refuses to use the additional 2 channels. Enabling WAAS causes 49 to pop back up just as in the beginning.

 

Whenever WAAS is enabled, I see spurious track points compared to the nice tight grouping I get with WAAS disabled.

 

I was able to select "New Location" once, despite it being grayed out, but it still did the same thing. Now "New Location is grayed out & I cannot select it. I have not tried a hard reset yet.

 

For comparison, my Vista C always gets satellites 48 & 51 at about 60% strength (48 hollow, 51 solid) for WAAS corrections & 51 (along with all other non-WAAS satellites) display "D".

 

I can't find much information on PRN 136 other than 1 reference to Inmarsat. This sure is starting to look like some sort of firmware bug for the HCx. I have the latest version with the "WAAS fix". I'll try a hard reset next.

 

Any idea what is going on here?

 

PS. I'm on the U.S. west coast.

[+EraSeek]

There is no 49 or PRN 136 as far as I know.

Your WAAS sat will fill in the bar and will cause other sats to display the D's showing corrections, but will not show itself corrected. They did in the past, but I don't believe they are monitoring themselves these days (although it may also have to do with the new high-sensitivity chips in the new units). I know 48 is not monitored and 51 is Non-precision. Both send good WAAS data.

On the new units (I have a 60cx) only one WAAS sat will be used at any one time, so you will see only one, which is all that is needed.

Once the WAAS sat signal is lost it will still correct up to 2 mins in Garmin units.

13 is a normal GPS sat and is operational.

You don't always get 12 sats to fill up your channels.

The 60cx has the Sirf chip. I believe the etrex H units have the new brand chips from Taiwan. Probably have some bugs as with all new products. SAT 49 would be a flaw.

[+EraSeek]

View all sats in real time and position here: http://www.nstb.tc.faa.gov/RT_WaasSatelliteStatus.htm

[brian.r.hamilton]

Thanks, I'm aware of the real-time status link you posted.

 

Here is where I found the only reference to PRN 136: http://www.gpsmap.net/Whatnot.html. It's listed as INMARSAT, 8 deg. E., reserved.

[brian.r.hamilton]

Is my Vista C considered that old already?

 

My HCx continued to display the "D"s for at least 10 minutes despite not having any WAAS satellite signals. It didn't give up until I disabled WAAS. I guess all this clearly indicates a bug. I wish I would have looked at it more closely before installing the new 2.3 firmware.

 

Does anyone else see the same behavior with their HCx? If so, what version firmware are you using?

 

PS. The HCx appears to use a chipset by MediaTek.

[+EraSeek]

Thanks, I'm aware of the real-time status link you posted.

 

Here is where I found the only reference to PRN 136: http://www.gpsmap.net/Whatnot.html. It's listed as INMARSAT, 8 deg. E., reserved.

 

I found no INMARSAT sats currently at 8E. I did find a spare in another position.

 

Here is what is at 8E 0north:

 

Hot Bird 2

NSSDC ID: 1996-067A

 

Other Names

24665

 

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

 

Launch Date/Time: 1996-11-21 at 20:47:00 UTC

On-orbit Dry Mass: 2800 kg

 

 

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

 

Description

Hot Bird 2 was a geostationary communications spacecraft of the European EUTELSAT consortium. With a constellation of 5 satellites, the Hot Bird family at 13 degrees E formed one of the largest broadcasting systems in the world. By fourth quarter 1998, the system was delivering over 320 analogue and digital television channels, as well as radio and multimedia services, to more than 70 million homes connected to a cable network or equipped for satellite (direct-to-home or community) reception. The Hot Bird satellites provided full coverage of Europe and also took in parts of Africa and Asia, including the entire Middle East.

[brian.r.hamilton]

It looks as though my HCx is displaying 49 for 48 (PRN 135).

 

Perhaps it never even tries to lock 51 because "48" is so strong (full bar on display). Maybe my Vista C goes after both 48 & 51 bedcause they are usually less than 2/3 strength.

 

I called Garmin last week & the technician said he would report the issue & get back to me Monday (2 days ago). Haven't heard anything yet.

[brian.r.hamilton]

I just looked at some data I collected yesterday & WAAS enabled seemed much better! I'm running some more tests today to confirm. If what I find today confirms what I saw yesterday, my Vista HCx is outperforming the Vista C by quite a bit with WAAS enabled!

 

Maybe the recent satellite changes were actually causing problems with WAAS & the satellite numbering issue is simply a display error.

[+Red CBX]

My Vista HCx seems to display 51 as "13" on both the graphic display and the strength bar. This bar is at the right of those numbered less than 33. Yesterday I saw two 13 bars. Seems like a "typo" in the display text.

[brian.r.hamilton]

I've seen satellite 13 displayed on the right & twice too but I didn't check to see if it was really satellite 51. It did indicate it was broadcasting corrections (displayed "D"). I didn't check to see if there were multiple satellite icons numbered 13 or 49. I'll try to remember to watch for some of these details, but I agree that it's looking mostly like a display bug right now.

 

However, today I noticed that with WAAS off on my HCx, my average position was quite a bit more inaccurate than my Vista C with WAAS off. I gathered track points every second for one hour, at the same time with each unit from the same stationary location outdoors. The Vista C error increased with WAAS off, but the average position was almost exactly the same as the average position with WAAS enabled. On my HCx, the average position with WAAS enabled is the same as my Vista C, but with a much tighter grouping of track points. With WAAS off, the HCx average position moved more than 20 feet for some reason. By the way, the data I took today also showed the HCx with WAAS off generating a grouping of track points as tight or better than the Vista C with WAAS on. Too bad the average location was a little off. I would need to do more reading & testing to be sure, but this could indicate a rounding error in some math in the firmware.

[+jotne]

Turn of Waas and save battery.

 

There are no use for Waas, since it does not give you any more accuracy on the ground.

Waas was primary intended for use with airplane.

 

Reflection from trees, buildings and other objects does even make more problems.

 

I have use Garmin GPS for 5 years and Waas have not given my anything.

It’s a marketing hype.

 

Do a search for waas here on the forum.

 

"accurate navigation system developed for civil aviation by the Federal Aviation Administration (FAA),"

http://en.wikipedia.org/wiki/Wide_Area_Augmentation_System

Edited August 17, 2007 by jotne

[+EraSeek]

Turn of Waas and save battery.

 

There are no use for Waas, since it does not give you any more accuracy on the ground.

Waas was primary intended for use with airplane.

 

Reflection from trees, buildings and other objects does even make more problems.

 

I have use Garmin GPS for 5 years and Waas have not given my anything.

It’s a marketing hype.

 

Do a search for waas here on the forum.

 

"accurate navigation system developed for civil aviation by the Federal Aviation Administration (FAA),"

http://en.wikipedia.org/wiki/Wide_Area_Augmentation_System

 

Bull!

Get the coordinates of an adjusted benchmark.

Input it to your GPS.

do a goto to that benchmark with WAAS off.

See how close you get and how stable your position is.

Turn WAAS on.

Allow it time to gather and impliment the almanac.

Now approach the benchmark.

See how close you get and how stable the position is.

try the same again another day when errors may be more or less. See which is better. Corrections or no corrections.

 

BTW your accuracy reading (EPE) is not an accurate reading, just a programed guesstimate.

[+jotne]

It's not bull.

 

It can give you some better reolution, but if you are placed far away from a ground station (that do sends correction to the sattelites) it wil not give you any better resolution.

 

It's also true that Waas is made for airoplane. Read wiki

Same with EGNOS

http://www.egnos-pro.esa.int/Publications/...act_sheet_4.pdf

 

It does user more CPU to compute WAAS, hence more power.

I do also write this from 5 years of using GPS

[+EraSeek]

It's not bull.

 

It can give you some better reolution, but if you are placed far away from a ground station (that do sends correction to the sattelites) it wil not give you any better resolution.

 

It's also true that Waas is made for airoplane. Read wiki

Same with EGNOS

http://www.egnos-pro.esa.int/Publications/...act_sheet_4.pdf

 

It does user more CPU to compute WAAS, hence more power.

I do also write this from 5 years of using GPS

 

I've used GPS's since the 90's. Again you are wrong. The whole concept of WAAS is a modeling of corrections so you are not limited by proximity of ground stations as you are with DGPS. The stations and the masterstation makes a model (a grid) of corrections. Your GPS looks for where it is in that grid and applies the proper corrections. The corrections are not station based as in DGPS.

 

Certainly it has an important application to air traffic, but it also applies to other things and users, including stationary cell phone towers. The accuracy of GPS has several functions, namely the world' most accurate means of time transfer, and navagation (also a function of timing).