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  1. #371
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    @Neil
    Hotfix is only to help with the initial startup acquisition time and does not affect acuracy while navigating.(If a full bouquet of sats has been aquired of course.)
    It's basically a database of the Sat Status at the time you switched the unit off or put it into battery saver mode.
    Once the unit wakes up it quickly locks on to known sats by the process of prediction.
    The data is in the GPX folder and I suspect in NVRAM as well.
    Current Model 3490's GPX folder is totally different to 3790 (Converted or unconverted). This is due to different GPS Chipsets.
    Another thing that I've noticed is that the 3490 does not give you message about lost satelites(like the 1300) when you go through a short tunnel.
    I think that they've done some magic in the firmware.
    Last edited by dasilvarsa; 10th May 2013 at 07:33.
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  3. #372
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    @dasilvarsa
    Yes thanks, but i'm aware of what hotfix is for and that comment of mine was in regard to the slower lock-on response from the converted units compared to the original units and whether that's due to the fw/hw incompatibility or Hotfix simply now not working in the converts. I've raised it before, it's a little 'out of context' in my post before yours and i can see that it may be taken as referring to the established/fully locked-on accuracy. However, on that subject and the notorious '3 metre accuracy' there are undoubtedly other software 'tricks' to help with that [beyond my ken] and your clarification prompts me to raise this question: Do they also work as they should in the converts? As usual, i wouldn't know but just putting it out there.
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  4. #373
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    Quote Originally Posted by Neil View Post
    The ultimate definitive test imo would be simultaneous track logs of (1) 3790, (2) 3490, (3) 37>34 conventional convert [with reported good accuracy like mine & Caty's], (4) 37>34 conventional convert [with reported bad accuracy like yours & isg's], (5) 37>34 Kunix #1;(6) 37>34 Kunix #2, and (7) [if it happens] 37>34 Kunix #3. But who's gonna manage that, unfortunately.
    Where to send my 3790 unit? I'm not joking! It is almost useless with current accuracy. Yesterday my S III with CoPilot has much better accuracy than nuvi. I'm waiting for 3597 appearance and 3790 will remain for testing purposes only. I thought to sell it, but with such accuracy....

  5. #374
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    @isg
    I seem to remember that you said the reported accuracy does not return to the fabled '3 metres' when you reconvert to 3790. But is it really bad when navigating too, i.e. do you have a similar or near-similar crappy accuracy as with it converted to 3490? If so have you tried reformatting internal memory using RMPrepUSB as you said you might try a few days ago?

    @dasilvarsa
    Your comment about 3490 not 'losing' sat sig in tunnels: I forgot when i replied before to say that it's 'tunnel aware' and it assumes you are travelling at the same speed in the tunnel as when you went in. I find it a bit disconcerting, 'cos you might go in doing 80 klicks in a long tunnel but catch up to a traffic jam going only 20 or 30. Does it then just 'park' after the tunnel exit when it can't re-catch the sats, although it's calculated that it should be outside? Sorry, bit OT here. I think there's a thread, or at least some posts about it somewhere.
    I recall Giomen posting about it, maybe do a search for it if you want more info.
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  6. #375
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    Quote Originally Posted by Neil View Post
    @isg
    I seem to remember that you said the reported accuracy does not return to the fabled '3 metres' when you reconvert to 3790. But is it really bad when navigating too, i.e. do you have a similar or near-similar crappy accuracy as with it converted to 3490? If so have you tried reformatting internal memory using RMPrepUSB as you said you might try a few days ago?
    3490->3790 I have done it once using RMPrepUSB, but have copied old files structure from archive copy made 2011. Unfortunately this week have no enough free time to make it with WebUpdater i.e. to start from the very beginning. After returning to 3790 I have never reach 3 m. accuracy. Hot fix is OK and first 5 minutes or so unit locks on road well. But then.... it is a complete mess. Of course unit has it's good times, but bad times are much more and make it totally unreliable. I even started to think that it might be the case that unit's antenna is broken. I have dropped unit several times . This weekend I will try and will report accordingly.

  7. #376
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    Continuing our interesting discussion about precision of 3490, converted or not, in this post I present another test, this time only with the original 3490, but in a different environment than the one I did earlier (post #368). At first I used the same 3490 real and a 3790 mod with Kunix # 1 fw (3790 boot.ini 3490 fw_all), but in an urban environment with many high buildings and trees in almost all the way. Both gps had a very similar result, apparently weak, as can be seen in the tracklogs off-road and lock-on-road, on the satellite photos from Google Earth. The tracks showed that the off Road were irregular and very imprecise, with considerable deviations of the roads. The tracks lock-on-road sometimes had some crazy moments deviations, such as jumps to other routes and other aberrations. Compared to mine, the tracklogs off road of Neil’s test (post #346) were much more regular in its trajectory, both for nuvis that were more accurate as for the inaccurate. So, which the question: after all, the difference to the tracklogs of my test (post # 368) was due to quality of gps units tested or what? The answer, I believe, can be from the analysis of tracks that now present. Despite having been made only with the original 3490, the tracklogs off-road (pedestrian mode) and lock-on-road (trip log enable) were quite regular and accurate, staying on the real road almost all the way, as seen in the pictures attached.

    After all so what can explain such differences? Answer: the environment test. My test of the post #386 was made in a densely populated area with many buildings, trees and other obstacles. Besides the decrease of signal strength and number of satellites tuned has another very important complicating factor in these environments: the reflection of satellite signals that occurs in environments with many buildings, greatly increasing the inaccuracy in the recording of GPS positioning. Interesting is that the reflection signal can trick the gps in your calculations intensifying sometimes falsely signal strength of satellites, base time to calculate the position of the same and more, distorting the accuracy shown on screen (more or less) and in recording of tracklogs. How to know that? Just check the tracklogs off-road and see the distortions: in those recordeds in environments free of these obstacles and reflexes, the tracklogs are accurate and precise and the screen accuracy is almost constant. In my test was 3 meter, practically 100% of the path, that was not an absolute value but walked over to of the reality most of the time.. In tracklogs recorded in environments with many buildings were the opposite: imprecision and irregularity of tracklogs.

    So, if any of us says not having problem with the accuracy of the 3790 converted, it seems that may not necessarily be a mere matter of a few different hardware versions, but the environment in which the measurements and navigation usually occurs. For example, let's take the Neil’s case (sorry, lol ..) in post 346: we observed by satellite photos that he seems roaming through open environments, residential areas without tall buildings, near the coast, in short, environments for privileged people, lol .. As a result of the Garmin lock-on-road system, that fixes almost all of the inaccuracies in these environments, the result of the 3790->3490 fw does not show abnormality. If anyone has any doubt about these statements can check by doing your test, even if only with his one gps, recording tracks simultaneously in lock and off road mode in both environments suggested: places with many buildings and open spaces, and check on Google earth, pretty easy..

    Conclusion, now I am more satisfied with the level of accuracy of my 3490 (which even I thought about selling, lol) and best of all, I believe that I now understand a little more why occurs some distortions and aberrations in relation to apparent (on screen) and real (tracklog off road) accuracy. Lack doing this test with 3790 converted with Kunix fw # 1 (in the open environment) and with 3790->3490 fw full (in adverse environment, since Neil has done this test in open environment with this fw), what I will do as the unit back to my hands.. Thus, I believe that it is possible to reach consistent conclusions about the accuracy of GPS road in urban environments with a single device and different firmwares, because most of us do not have shop or collection of gps. Having multiple units is a privilege of a few but compare various units, is undoubtedly the ideal condition…Luckily we have a expert and “collector” that is always ready to assist us


    Legend tracks: (of the same gps, simultaneously recorded)

    - 3490 off road: red
    - 3490 lock-on-road:yellow



    [Only registered and activated users can see links. ] One of the rare moments of imprecision, justifiable by the presence of buildings and trees



    [Only registered and activated users can see links. ] Lock-on-road misplaced and off-road track on the path indicates error in the gps map (where the track was fixed lock-on-road)


    Below, another rare error in path, with measured deviation of 28 meters (buildings and trees). Sounds like a clear case where the GPS uses satellite signals reflected in edifications ..
    Attached Images Attached Images
    Attached Files Attached Files
    Last edited by angelozip; 15th May 2013 at 02:05.
    Nuvi 2689; 3490; Etrex 30; Oregon 200 (from Approach S5)

  8. #377
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    Had both Nuvis the same position in your car? Nuvi position is important too, wrong position can lead to bad tracks.
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  9. #378
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    Quote Originally Posted by catymag View Post
    Had both Nuvis the same position in your car? Nuvi position is important too, wrong position can lead to bad tracks.
    In the previous post I used only a GPS, the 3490 real. His position was improper, that is, at the bottom of the dashboard, just below the windshield, near at the gear shift. Throughout the test I left the gps in satellite page screen and apparent precision was 3 meters, always. Best of all is that the result of the off-road tracklog was great. Maybe if the gps was on the windshield, as it should be, the result was even better. So, I can deduce that small variations in position of my GPS in my car, does not matter.

    In relation to the test of the post #368 at that I have used 2 gps, both side by side on the panel and in horizontal position, still produced tracklogs off-road very similar between themselves and appropriate to the external environment (unfavorable for satellite acquisition, buildings, trees..). As in other measurements I've done, but not published, the small variation of the position of these devices not imply bad tune.

    As a result overall I am quite sure of my conclusions and anyone who wants to challenge or confirm, feel free, but make up from of concrete and well collected data or showing some logical inconsistency in my analysis of data. Without reliable data on which to base our affirmations are mere opinions or matter of faith..
    Last edited by angelozip; 15th May 2013 at 03:32.
    Nuvi 2689; 3490; Etrex 30; Oregon 200 (from Approach S5)

  10. #379
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    To try to kill your unit is not so bad thing in the end of the day, if you have the support of Noeman experts & members.

    As you [Only registered and activated users can see links. ] that I did my very best to "kill" my beloved unit and the results are:
    1. I have no bluetooth
    2. Due to new traffic soft no single traffic provider appears despite all of the except one were installed in Garmin factory.
    3. Some other functions did not operate well, but soon or later I'll fix them all.

    4. Accuracy - here is the miracle - now I have accuracy of 3-4 meters in stand still position and more important - have 8 - 13 meters average accuracy driving. This morning in city conditions, no tall buildings, but cloudy weather with drops of rain and relatively a lot of trees alongside the road my accuracy varied from 8 to 16 meters , which is perfect accuracy in my mind.
    I'll not do anything on unit till Wednesday, as I have on Tuesday a + 500 km. trip passing and driving in urban areas with tall buildings and heavy traffic and will report accordingly.

    So most probably one of the things which influence accuracy of transformed unit could by in good order of regions 41 and 48.
    What do you thing about that?
    Last edited by isg; 17th May 2013 at 08:03.

  11. #380
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    @isg
    That's very good news considering the lousy accuracy you had previously. It would be good if you can do track logs for your big trip.
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