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  1. #251
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    Quote Originally Posted by Kanopus View Post
    I didn't mean GPS accuracy in general but specifically accuracy value displayed on satellite screen. In my opinion it is totally useless as an criteria to estimate general GPS accuracy for the reasons I stated above.

    Edit: maybe you know saying: garbage in, garbage out. If you use garbage as a test criteria then you will get garbage as a result of your research.
    Hi,

    So, please, what do you think to help with your criteria?

    Maybe discover diferents things...


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  3. #252
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    Quote Originally Posted by dasilvarsa View Post
    No Photoshop it's called Hotfix

    If I delete the /.System/GPX Folder at this location it never picks up satellites even after waiting 20 minutes.

    Then I go outside to the Garden and it picks up sats First 27m after a minute 14 meters another minute 7 meters another minute 3 meters, Then stays 3 meters.
    Then I come back to this location which is under a steel roofed carport and it stays 3 meters for about 5 minutes and then it starts to drop gradually.
    I think that this screen is indicative but it has a lot of "smoke and mirrors" created magically by the firmware.
    The /.System/GPX folder holds the files needed for the hotfix. It already knows which birds are flying overhead at any time of the day. (It learns all the time)
    It actually takes a couple of days to learn all 32 Sats. After deleting the folders in the evening the next morning it takes a long time to get a 3Meter Fix.
    I believe that deleting the GPX folder is the same as cold start. (Starts without knowledge of sats)

    I joke...
    sorry!!

  4. #253
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    Quote Originally Posted by Neil View Post
    I don't believe for i second that dasilvarsa would do such a thing as photoshop an image before posting it. I've seen that 3 metre so-called 'Accuracy' with similar low sat. lock numbers and signal strength on original 34/35xx units. I've stated before and will again categorically that i do not believe it is possible for a non-professional gps device without SBAS enhancement to consistently maintain that accuracy under a wide range of conditions. I assume the 'photoshop or what?' comment was a joke. Kanopus is right in that many of the tests (mine included) are not very scientific (garbage in, garbage out) but more anecdotal. Even the side-by-side tests rely on the units accurately reporting their true accuracy are suspect. Consistent 3-4 metre accuracy shown by 34/35xx is garbage imo. Angelo has done static tests over a permanent mark, can't get more reliable than that. But the big problem is moving accuracy for some units. I still think that the only real answer is by modding 37xx gps fw into the 34xx to overcome the hardware incompatibilities which are obviously worse in some 37xx coverted to 34xx. I can't do it, can any of you other blokes without 'Navigation software expert' behind your nicks do it? If not, we should all shut up and let the experts like Loly & Kanopus find the solution because i don't know if we can add anything more that's constructive unless the further tests are totally scientific and tailored, but really what will they prove? That some units have 'bad' accuracy, which their owners already know? We can do all the further testing we want, but more tests won't solve the problem ....
    Of course that was a joke...i've respect for all OUR work and OUR test for best accuracy

  5. #254
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    Just found something:
    Returning to 3790 from 3490, I was shocked from very very poor accuracy.
    Well I deleted the 3 files in \.System\GPS\ARC.BIN, BEE.BIN, mt.nvm and everything was ok.
    If you have problems you may try to improve accuracy and in this way.
    Last edited by isg; 25th February 2013 at 20:16.

  6. #255
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    Quote Originally Posted by isg View Post
    Just found something:
    Returned to 3790 from 3490 and I was shocked for very very poor accuracy.
    Well I deleted the 3 files in \.System\GPS\ARC.BIN, BEE.BIN, mt.nvm and everything was ok.
    If you have problems you may try to improve accuracy and in this way.
    Yes, Must do this to clear the "Hotfix Information" Nuvi will re-create files with new info.
    If you do cold-start it will have the same effect.
    You can also just delete the GPS folder - Nuvi Should recreate the folder.
    If you decide to re-convert to 3490 do this again after re-convert.
    The difference between stupidity and genius is that genius has its limits.
    Albert Einstein.

  7. #256
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    Checking the option Cold Start (screen gps / height / cold start), I realized that the previously recommended procedure in this topic does not work, that is, select the option and restart the gps does not enable Cold Start. This option is very useful because it erases, probably, ephemerides, almanac and other information that are recorded in parts of protected memory of gps. To work effectively we must do the following: select the Cold Start option and then "Start Single" in the upper left corner of the screen. Note that the synchronization table is reset and restarted. Go back to the satellite screen quickly and check really the true reboot of satellites.

    With regard of the "Predicted Eph" option (ephemeris predicted) what would it be? How Ephemerides are highly detailed information of orbits used by GPS to calculate the position of the satellites (not valid for more than 4 hours), I assume that enabling this option, the gps would be using Ephemerides data already stored to calculate the orbits of satellites. The Cold Start option is that would restart and would store the new Ephemerides information (and perhaps the almanac) sent by satellites (in hotfix files and, maybe in firmware too). To enable the "Eph Predicted" the procedure is the same as Cold Start. Thus we enabled the option can be observed in the table that the tuning of the satellites comes with Ephemerides, ie, are being used Eph data already stored in the GPS. Perhaps this option can be useful in places with difficult and/or low tuning satellites, but in practice does not seem to be useful in our case. When we enable the Cold Start option is observed in the table that gradually located and synchronized satellites and in sequence the Ephemerides data are received, ie, new data from eph, what really matter.

    Finally, a recommendation to improve the "accuracy" that appears on the screen: as suggested by isg​ in previous post, delete the files in the folder System / GPS (arc.bin, bee.bin, mt.nvm). In satellites page we observe that restart of satellites, an apparent Cold Start, but the "accuracy" can go bad (happened to me). After satellites synchronization stabilized, make the procedure of Cold Start as described above and "accuracy" will improve immediately. Just not done yet comparative tests with the 3790 to see how much improved in relation to the original, or how long will last the improvement.

    In short: I think always important to understand the reasons and above all, do not be afraid to expose doubt or unawareness, we are all learners, to varying degrees, including experts .. We are learning from each other .. Along this line who know clearly identify, or supposedly, the contents of files arc.bin, bee.bin and mt.nvm (hotfix files and..) would be giving a good collaboration.
    Last edited by angelozip; 25th February 2013 at 17:37.
    Nuvi 2689; 3490; Etrex 30; Oregon 200 (from Approach S5)

  8. #257
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    Hard Reset and ClearNonVol causes an even more comprehensive Reload of Satellites and EPH

    If you go to GPS SNR Logging Page you will see that the table is totally empty.

    "Brain Freeze Cold Start"
    Last edited by dasilvarsa; 25th February 2013 at 20:59.
    The difference between stupidity and genius is that genius has its limits.
    Albert Einstein.

  9. #258
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    Quote Originally Posted by dasilvarsa View Post
    Hard Reset and ClearNonVol causes an even more comprehensive Reload of Satellites and EPH..
    The purpose of the post was not to show that Cold Start is not done by any means, but that it was not performed following the procedures that have been indicated and that alone seems to produce no effect on the "accuracy", first point. All those that installed the 3490 firmware also cleared the nonvol memory and know very well that not bring real improvement in the "accuracy" with this procedures.

    Everything indicates for me, in hypothesis, to a set of procedures that can cause improvement, but the explanations are still obscure. It seems that some information not desired is stored in any memory region, or file, which is not eliminates by Clear Nonvol. In my test, the set of procedures indicated (delete files of System\Gps folder + cold start) immediately improved the quality of the tune and in sync speed of satellites, what not happened before (if the variables are already with the best definitions, no noticeable improvement occurs). Such procedures are easy to implement, requires no effort and has no risk, it's worth trying.



    "Brain Freeze Cold Start"
    Last edited by angelozip; 26th February 2013 at 00:14.
    Nuvi 2689; 3490; Etrex 30; Oregon 200 (from Approach S5)

  10. #259
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    Cold Start does improve "Reported accuracy" on 3490.
    Before doing Cold Start "Lolypop Method" I had 9 meters "reported accuracy" indoor.
    After Doing Cold Start "Reported Accuracy" shows 3 Meters, But after a few weeks it goes back to 9 meters "reported accuracy".
    If you delete the GPS Folder and then do "Hard Reset" straight away it takes long to find satellites and yesterday evening I had to go outside to get sats.
    After a long time I did get accuracy of 3 meters. This morning it took a while again to capture the remaining sats.
    It took a few minutes for the Bars to Change from Hollow to Solid.(Needs to get actuall data from the Sat to change from Hollow to solid)
    Actually your Method does work as well but it does not get "fresh data" It uses Historical Data from NVRAM or FILES.
    The reasoning Here is that it happens very Quickly.
    By Erasing both NVRAM and FILES you can be ensured of "Fresh DATA" "Takes very Long to Get Sats but if you wait long enough "Reported Accuracy" is good.

    When you Downgrade firmware Hard Reset is forced by Garmin Firmware, NVRAM is cleared and Sats are totally re-loaded.

    When you Upgrade Firmware to the next newer Level Generally speaking this is not done.
    Last edited by dasilvarsa; 26th February 2013 at 08:37.
    The difference between stupidity and genius is that genius has its limits.
    Albert Einstein.

  11. #260
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    I agree. infact, when i've my old 37>34 with bad accuracy, i've try to delete GPS folder, clear nonvol, replace GPS folder with other used that have good accuracy but nothing. Now i've good accuracy but i must do convert to 37>34 and then 37>34 with old firmware and delete all system's file (GPS folder too of course, read post up). Of course first time i start nuvi, i've wait many time for fix but now i've good accuracy, 4-5 meters in my city, but never like 37xx that in my city is 3-4 meters
    Last edited by giuseppe66; 26th February 2013 at 10:12.

 

 
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