Thread: About 37xx converted to 34xx satellites reception accuracy

Well, I am sorry once again contradict our competent collaborators friends. My conclusions (partial and subject to more tests, as always) were based on data collected in gps that I tested. As Neil has concentrated its tests in Kunix 's fw # 2, I decided to focus on #1. In despite of the statements of Neil and Kunix that the boot.ini of 3790 + 3490 fw_all is inefficient in accuracy, was not quite what I noticed in my tests. In fact the precision shown on the screen of this fw is similar to the 3490 full_fw, but the only Kunix_fw that proven unequivocally increased inaccuracy was the # 2 tested by Neil, as we see in the tracks that he published. In my case I compared the kunix # 1 fw (post 310) with a nuvi 3490 real and once again I was disappointed with the results, but this time not with the fw Kunix’s, but with the performance of my 3490, lol .. Turns out he had practically the same performance on 3790 mod with fw mentioned, same margin of error. Importantly, the tests were conducted in urban area with many buildings and trees, ie, areas of poor signal and also to emphasize that the GPSs was not set in the windscreen, but in horizontal position on the panel, really a condition not very suitable.

The basis of analysis were 2 tracklogs (per gps), recorded simultaneously in each gps (4 tracklogs total): off-road (pedestrian mode, 1 in 1 sec) and Lock on Road (trip log enable). Thus in addition to the “real” track record in the "Logs/Gpx" folder, we also have the track lock-on-road on “Current.gpx” recorded in the folder /GPX, that can be downloaded by Basecamp (the other track has to be imported from the Logs folder). Having two types of tracklogs from a single gps and recorded simultaneously can be very interesting to analyze. The lock on road catches the track, based on the map in use, and the off road track is independent of it. When we open the tracks in Google Earth with the track Lock on Road, we first give a margin of accuracy of the map, because if the tracks is locked out of the roads, certainly the map is misaligned (higher probability of error than photos satellites). But what matters is the right relation between accuracy "real" and apparent (shown on screen). We can observe behavior of these crazy tracks when the satellite signal is weak or is lost and its relationship with the "accuracy" shown on the screen usually with high values of inaccuracy. Garmin's software tries to position the vehicle in a road and sometime jump in other roads or with deviations amazing. Are situations that when we follow the routed gps navigation may involve errors such as wrong indication of streets to below, delays in recalculating when we left the route and other things not so pleasant symptoms that I and other users have experienced in practice with the firmware 3490 full in 3790. Fortunately the lock on road usually corrects these distortions, which bother more for those who make frequent use of the routing gps. Even with this drawback I prefer to use the firmware of 3490, to be clear, because it has advantages, for me the accuracy to drag the screen is the biggest one (very bad in 3790).

But it is from of the off road tracklog that we can extract information more effectively and realize the relation between accuracy "real" and apparent. When analyzing such tracks in Google Earth, the deviations of this tracks from the midline of the track “lock on road”, if it is centered in the middle of the road (therefore, map and satellite photo are right), it is possible to check the accuracy of the deviation in meters (measure tool of G.Earth). Most likely the average values of these measurements must match, or come close, the values in meters of "accuracy" shown on the screen of the GPS. Would have to make such observations at the time of testing, which is difficult for just one person that's driving.
Besides the comparative test between 2 gps with based on tracklogs I also did a practice test in routing with Kunix’s fw #1 in 3790. I drove for over 2 hours straight in a metropolitan area that I did not know following the gps routing and, surprise, there was not a mistake! Honestly I elect this firmware as the best I”ve ever experienced for 3790. I suggest that who have 3790 to try this firmware and repeat this tests, this version has no risk (not even have to install the "logo" of the Garmin 3490, it became something different, but I left anyway). For me 100% satisfaction, despite its "precision" of screen be below of the 3490 real.

The previous tests I did with 3790 with full 3490 fw were practical, day to day use, so would need to repeat the tests accurately analyzing tracklogs (now with real mode off Road in pedestrian). The problem is that lent this gps to a friend wich was travelling and only have back in 2 weeks.But the good thing is that I bought another 3790 and so in 15 days to have two 3790 and one 3490 to play, at least for awhile. At last, if there is a passion here, everything indicates that it is by knowledge and reason, a pleasure without nasty side effects, except, sometimes, when we went wrong our guesses

**3790 (V6 8GB 035 DA TC HP GM) mod Kunix #1 fw
3490 real (V7 2GB 036 DS TC GTL) sw 7.90

Legend tracks:
- 3490 off road: blue light
- 3490 lock on road: blue

- 3790 off road: red
- 3790 lock on road: red light

(click to increase)
[Only registered and activated users can see links. ] Path out of the official road, place of low reception satellites signal. Garmin software trying to lock on road with great distortion.

[Only registered and activated users can see links. ]Another example of track "lock on road" crazy due to loss or weak satellite signal which can result in errors while navigating with GPS routing. Unfortunately in this case was failure of 3490 real (blue track)

[Only registered and activated users can see links. ] Attempt to have approximate accuracy in meters from the track in relation to the terrain, taking the middle line of the road or track "lock on road"

[Only registered and activated users can see links. ]

[Only registered and activated users can see links. ]

Originally Posted by angelozip

Well, I am sorry once again contradict our competent collaborators friends. My conclusions (partial and subject to more tests, as always) were based on data collected in gps that I tested. As Neil has concentrated its tests in Kunix 's fw # 2, I decided to focus on #1. In despite of the statements of Neil and Kunix that the boot.ini of 3790 + 3490 fw_all is inefficient in accuracy, was not quite what I noticed in my tests. In fact the precision shown on the screen of this fw is similar to the 3490 full_fw, but the only Kunix_fw that proven unequivocally increased inaccuracy was the # 2 tested by Neil, as we see in the tracks that he published. In my case I compared the kunix # 1 fw (post 310) with a nuvi 3490 real and once again I was disappointed with the results, but this time not with the fw Kunix’s, but with the performance of my 3490, lol .. Turns out he had practically the same performance on 3790 mod with fw mentioned, same margin of error. ...........

Well, actually what I said was that from my brief side-by-side of Kunix's 37 boot + 34 fw_all tested [kunix #1] against my conventionally modded 37>34 is that they appeared to have the same accuracy, not 'the boot.ini of 3790 + 3490 fw_all is inefficient in accuracy'. From my [Only registered and activated users can see links. ]:

Sat accuracy seems the same as my other convert, varied 4 to 10 metres today in mostly overcast suburban running (no tall buildings) in half-hr test. This unit and my other 2 showed rock solid 3 m before as 3790s which i find to be unrealistic in any case [just artificially enhanced with hotfix?]. From full off, about 4 mins until 'ready to navigate'. From standby 60-70 m quickly backing off to 8/9 m between 30 sec to a minute. I'd suspect hotfix is not working on these converts because while navigating there seems to be no problem, at least with both my 37>34.
Sat accuracy seems the same as my other convert, varied 4 to 10 metres today in mostly overcast suburban running (no tall buildings) in half-hr test. This unit and my other 2 showed rock solid 3 m before as 3790s which i find to be unrealistic in any case [just artificially enhanced with hotfix?]. From full off, about 4 mins until 'ready to navigate'. From standby 60-70 m quickly backing off to 8/9 m between 30 sec to a minute. I'd suspect hotfix is not working on these converts because while navigating there seems to be no problem, at least with both my 37>34........

Keep in mind that my conventionally modded 37>34 [full 34 fw] and Caty's both have far better reported accuracy than yours and isg's. I still regard my conventionally modded 37>34 to have acceptable accuracy. I also absolutely conclude that yours doesn't. I also continue to ponder the effect of hotfix not working on any of the converts [if that is the case]. I wish i had a real 34 to compare, but the 3590 was the closest i could think of and it didn't appear to compare well to 3790 original. The other thing is that I have never properly tested my 2nd 37 as a conventional convert, only as both kunix's mods, so i don't know if it's accuracy as that will be 'good' or 'bad'. I do want to keep the virgin 37 totally original as a standard, so that only leaves me with 2 other units to compare as various mods.

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.