Welcome guest, is this your first visit? Click the "Create Account" button now to join.
Page 6 of 40 FirstFirst ... 4567816 ... LastLast
Results 51 to 60 of 397
  1. #51
    Garmin/GPS Systems GMod.

    Neil's Avatar
    Join Date
    Aug 2011
    Location
    Oz.
    Posts
    7,406
    Rep Power
    1435

    Default

    @tom1807

    Could you do a test on your 3790? Check accuracy with WAAS/MSAS on and off, and report.

    ......................................................................................................................

    For others, maybe as unsure as i am about the 'WAAS-type' capabilities of 3xxx:

    [First, a Terms explanation in case the several terms are confusing: MSAS is the Asian equivalent of NA's WAAS and EU's EGNOS. All these systems are compatible and collectively called SBAS, the correct (but rarely used) generic term for such systems. That is, a WAAS capable unit receives MSAS and EGNOS and vice versa. I'll just the term WAAS, it's easier.]
    WAAS was first developed for Aviation, particularly for instrument approaches (non-visual condition) and other precision uses. My opinion is that it's not necessary for safe and normal operation of civilian ground vehicle navigation as we just don't need that 'precision' in a car GPS unit, but i've seen first hand the difference WAAS makes in the air and it could be a 'life or death' difference there.

    Ground devices like some Garmins have 'piggy-backed' for a free ride by obtaining the signals from the WAAS sats to increase their accuracy. It's maybe not available to 3xxx units, but i don't know one way or the other.

    In regard to the capabilities of WAAS-type systems to minimise error. The ground stations (precisely fixed coordinates) receive data from Sats, compare the sat's info given on the station's location to it's actual location, calculate the error if any, then transmit that back to a sat which rebroadcasts the correction to WAAS capable receivers, but not to non-WAAS receivers of course. So in that sense, in a perfect world with no sat being 'off', the accuracy of a unit with WAAS off would be the same as when it's on, as stated in the info quoted by Caty.

    In Post #37 giuseppe66 said his Nuvi 765 EU version has accuracy of 6-7m, however his Nuvi 765 TW version gets 3-4m with WAAS on test at same time. With WAAS off he gets same precision in both. That would seem to indicate that 765 EU has WAAS capabilities because his 765 TW is a convert from EU, not an original.

    To settle this, is WAAS available to US/EU 37xx/34xx units? It clearly is available in at least some Nuvi units other than 3xx/6xx. i.e. Tom's 3790TW and (apparently) in giuseppe66's 765 EU>TW convert. The info from Caty is helpful but somewhat dated as she points out. These 3xxx units certainly weren't around in 2008, or even in 2010 were they? Aren't they 2011 and 2012 releases?

    The other consideration is how 'truthful' is the accuracy reading on the original US/EU 3790's anyway? Mine seems to always read 3m when there is a clear or only partly cloudy sky. I'm getting suspicious that it actually can constantly maintain that degree of accuracy in practice, even if it is WAAS capable. Is it pre-programmed in the fw to show an artificially 'good' reading?
    Last edited by Neil; 30th January 2013 at 23:11. Reason: clarity.
    'Thanking Posts' are banned. To thank someone, and/or to see hidden links and content, use the [Only registered and activated users can see links. ] button below left of the helpful post then refresh your browser [F5 key]. 'Thanking Posts' are banned.
    Please don't spam. Posts serving no purpose other than to thank or to ask about hidden links are trashed or deleted, it's GPSPower's policy. Please don't spam.
    [Only registered and activated users can see links. ] should make their first post as a new Intro Thread in [Only registered and activated users can see links. ].

  2.    Advertissements


  3. #52
    Important User
    Join Date
    Dec 2010
    Location
    Somewhere over the Rainbow
    Posts
    347
    Rep Power
    44

    Default

    What I remember from my Nuvi 350 is that GPS accuracy slightly decreases when WAAS/EGNOS turned on but WAAS/EGNOS signal is not available or too weak.

  4. #53
    Garmin/GPS Systems GMod.

    Neil's Avatar
    Join Date
    Aug 2011
    Location
    Oz.
    Posts
    7,406
    Rep Power
    1435

    Default

    Voyager, interesting that you experienced a decrease in accuracy with WAAS on, regardless of its signal being absent or too weak. Why do you think that was? Do you still have the 350?
    EDIT: Do you mean the measurement decreases (e.g. 6m to 4m) or it's accuracy does (e.g. 4m to 6m)?
    Last edited by Neil; 30th January 2013 at 23:17.
    'Thanking Posts' are banned. To thank someone, and/or to see hidden links and content, use the [Only registered and activated users can see links. ] button below left of the helpful post then refresh your browser [F5 key]. 'Thanking Posts' are banned.
    Please don't spam. Posts serving no purpose other than to thank or to ask about hidden links are trashed or deleted, it's GPSPower's policy. Please don't spam.
    [Only registered and activated users can see links. ] should make their first post as a new Intro Thread in [Only registered and activated users can see links. ].

  5. #54
    Navigation software expert

    Giomen's Avatar
    Join Date
    Apr 2009
    Location
    Suomi-Russia
    Age
    49
    Posts
    2,579
    Rep Power
    589

    Default

    Usually I could see a new satellites with number higher then 32 on satellite page of compatible devices with WASS enabled! Anybody see something like on our disputed devices?
    Love your wife? Buy yourself a GPS for answering to her favorite question: "Dear, where are you?".

  6. #55
    Navigation software expert

    Giomen's Avatar
    Join Date
    Apr 2009
    Location
    Suomi-Russia
    Age
    49
    Posts
    2,579
    Rep Power
    589

    Default

    Quote Originally Posted by Neil View Post
    Voyager, interesting that you experienced a decrease in accuracy with WAAS on, regardless of its signal being absent or too weak. Why do you think that was?
    I have the facts of decrease in accuracy with WAAS on in Russia. Accuracy on satellite page was be greater - even 2 meters. But real position was so far of the truth - even about a few ten of meter. It was not surprise. The closest ground station was in thousand of km in absolutely different day time zone, atmospheric and weather conditions. Nevertheless GPS catched signal from nearest WAAS broadcasts sat zone (stationary orbit - Inmarsat probably).

    So we was strong recommended to disable WAAS in our locations!
    Love your wife? Buy yourself a GPS for answering to her favorite question: "Dear, where are you?".

  7. #56
    Garmin/GPS Systems GMod.

    Neil's Avatar
    Join Date
    Aug 2011
    Location
    Oz.
    Posts
    7,406
    Rep Power
    1435

    Default

    Quote Originally Posted by Giomen View Post
    Usually I could see a new satellites with number higher then 32 on satellite page of compatible devices with WASS enabled! Anybody see something like on our disputed devices?
    See this pic, from my post [Only registered and activated users can see links. ], 3490 convert is showing sat 153:

    37341

    Does that mean anything special?
    'Thanking Posts' are banned. To thank someone, and/or to see hidden links and content, use the [Only registered and activated users can see links. ] button below left of the helpful post then refresh your browser [F5 key]. 'Thanking Posts' are banned.
    Please don't spam. Posts serving no purpose other than to thank or to ask about hidden links are trashed or deleted, it's GPSPower's policy. Please don't spam.
    [Only registered and activated users can see links. ] should make their first post as a new Intro Thread in [Only registered and activated users can see links. ].

  8. #57
    Navigation software expert

    Giomen's Avatar
    Join Date
    Apr 2009
    Location
    Suomi-Russia
    Age
    49
    Posts
    2,579
    Rep Power
    589

    Default

    At next time please make retouch of view in windscreen. In this case I will not be admire a nature and I will see only on sat numbers

    It is mean what you receive SBAS - but no info about 153 PRN now. I find PRN 155 only:
    http://www.gps-forum.ru/cgi-bin/forum/showpost.pl?Board=gpsgeneral&Number=139008&page=0&view=expanded&sb=5
    Love your wife? Buy yourself a GPS for answering to her favorite question: "Dear, where are you?".

  9. #58
    Important User
    Join Date
    Dec 2010
    Location
    Somewhere over the Rainbow
    Posts
    347
    Rep Power
    44

    Default

    Quote Originally Posted by Neil View Post
    Voyager, interesting that you experienced a decrease in accuracy with WAAS on, regardless of its signal being absent or too weak. Why do you think that was? Do you still have the 350?
    EDIT: Do you mean the measurement decreases (e.g. 6m to 4m) or it's accuracy does (e.g. 4m to 6m)?
    Yes I still have Nuvi 350.
    When I obtained my 350 WAAS/EGNOS wasn't widely available. I was curious about this feature and tried it on and off. When it was ON accuracy decreased. I don't remember exact values but about twice.

  10. #59
    Garmin/GPS Systems GMod.

    Neil's Avatar
    Join Date
    Aug 2011
    Location
    Oz.
    Posts
    7,406
    Rep Power
    1435

    Default

    Quote Originally Posted by Giomen View Post
    At next time please make retouch of view in windscreen. In this case I will not be admire a nature and I will see only on sat numbers

    It is mean what you receive SBAS ............
    HaHA! Very funny g-man. I would think that you freezing northerners should APPRECIATE a view of the great Australian Bush, even on a rainy overcast day. If the sun was out here you'd need your Ray-Bans on just to glance at those photos. But yes, if i see PRN153 or PRN155, (btw, on the Russian forum weren't they talking about 225 not 155 on that guy's etrex?), or for that matter any other sat numbered above 32 again, i will just simply do a screenshot and save my doing any cropping, as there would not be any need to prove that the units were side-by-side contemporaneously in that case ......

    All sarcasm aside, i'm pleased to see someone else using the term SBAS. Most ppl i talk to over here look at me strangely if i say that, then when i explain say 'Oh, you mean WAAS!' Now, back On Topic: Yes i know that it means the 3490 was receiving SBAS info, but my question was 'does that mean anything special' in regard to the accuracy problems. i.e. if the 3490 convert was receiving SBAS info but was showing a lesser accuracy than the original 3790 which wasn't getting SBAS, what's that mean when the sig strength reads about 60% for the SBAS sat 153? Shouldn't accuracy be better? Is this the reason some users have 15-20m readings, no SBAS info received?

    Also, am i right in believing this?: There are only 32 true GPS sats, with PRNs from 1 to 32 inclusive, therefore any other number displayed by a GPS device is definitely an SBAS transceiver sat? And because it's showing an SBAS sat does that mean it can also use/process the SBAS info, i.e. that it is 'WAAS capable' ?

    (Don't beat me up for asking these dumb questions, you're the one with GPS Software Expert after your nick).
    'Thanking Posts' are banned. To thank someone, and/or to see hidden links and content, use the [Only registered and activated users can see links. ] button below left of the helpful post then refresh your browser [F5 key]. 'Thanking Posts' are banned.
    Please don't spam. Posts serving no purpose other than to thank or to ask about hidden links are trashed or deleted, it's GPSPower's policy. Please don't spam.
    [Only registered and activated users can see links. ] should make their first post as a new Intro Thread in [Only registered and activated users can see links. ].

  11. #60
    Navigation software expert

    Giomen's Avatar
    Join Date
    Apr 2009
    Location
    Suomi-Russia
    Age
    49
    Posts
    2,579
    Rep Power
    589

    Default

    Neil!!! Sorry! I was sincerely going to go on pub with you and other man yesterday but as usually I saw a woman's short skirt and walked after her. Be patient - no sex pictures here! Woman's short skirt was a looking for 153 PRN description in Inet source about SBAS, when online searching for satellites in occasional link, at the end it was launching of missile into the carrier rocket that hanging over my house and spying on me (do you see new from Russia about "Зенит-3SL" today?).

    OK! Begin from bushes. I often dissemble about my sincere interest to advanced knowledge about GPS devices. Most of my discussion in a raised voice it is nothings for me. It is only workout for the mind! In my settled opinion GPS is means to achieve the other main purpose. The main purpose is locomotion. That is why on first place I have question where Neil is driving, Jesus Christ. And then I think about 37xx converted to 34xx satellites reception accuracy So the great Australian Bush is more attractive for me then photo of MT3351 chipset even on a rainy overcast day.

    Well, about workout for the mind actually!

    1) I have the belief what geometric dilution of precision (GDOP) is not very objective after I can see number less 15 meters on screen.
    http://en.wikipedia.org/wiki/Dilution_of_precision_(GPS)
    Too many other factors are trying to challenge that figure. Yes! SBAS must kill this factors by default on right device. But we look a bad DOP (fewer GPS satellites with bad dispersion) on it. Purity of the experiment with digit of accuracy blurred by different quantity and quality of true GPS satellites (not SBAS). But nothing prevents confirm the conclusion what right device (Nuvi 3490) clearly captures fewer GPS satellites.

    2) In my case above was EGNOS and not WAAS. I think no difference at all SBAS what present in world. All of them are working on GPS standard signal specification and so WAAS give in device text resource for the sake of brevity.

    3) SBAS is good thing! But as mentioned above it have GPS signal specification. Accordingly it works in full measure only with professional device that use several GPS channel simultaneously (L1, L2 and so on). It just gives a some increase in stability on Nuvi but not 100 percent positive result.
    Last edited by Giomen; 2nd February 2013 at 01:39.
    Love your wife? Buy yourself a GPS for answering to her favorite question: "Dear, where are you?".

 

 
Page 6 of 40 FirstFirst ... 4567816 ... LastLast

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
This website uses cookies
We use cookies to store session information to facilitate remembering your login information, to allow you to save website preferences, to personalise content and ads, to provide social media features and to analyse our traffic. We also share information about your use of our site with our social media, advertising and analytics partners.