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 Garmin nüvi forums
 New hidden menu : SNR Log and TTFF on nuvi 7xx
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tsmccull

21 Posts

Posted - 19 oct. 2008 :  01:51:27  Show Profile  Reply with Quote

Access by taping and holding elevation in sat screen[/center]

Anybody know what the SNR logging screen that you can get to from the satellite display in the 760 is for?

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gpspassion

94636 Posts

Posted - 19 oct. 2008 :  01:52:58  Show Profile  Visit gpspassion's Homepage  Reply with Quote
An undocumented hiddent menu? How do you access it from the satellite screen ?

Discounts and Assistance/Réductions et Assistance (Club GpsPasSion) / Où commencer?
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poppap

89 Posts

Posted - 19 oct. 2008 :  02:23:28  Show Profile  Reply with Quote
I tried to find it and found that if you keep pressing the elevation you'll get into that screen.



I think it's for measuring how long it'll take for the unit to acquire the satellites.


Edited by - poppap on 20 oct. 2008 09:45:16
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poppap

89 Posts

Posted - 19 oct. 2008 :  02:46:12  Show Profile  Reply with Quote
After testing further...

Nuvi 760 US w/ Sirf: TTFF = 00:39



Nuvi 765T US w/ MTK: TTFF = 00:55



Both unit placed at the same location, pressing the start button at the same time.

760 (Sirf) has faster Time-To-First-Fix, but seems like 765T (MTK) got stronger signal strength...

quote:
Carrier-to-Noise Power Density (C/N0). The ratio of the power level of a signal carrier to the noise power in a 1-Hz bandwidth. This is a key parameter in the analysis of GPS receiver performance. Nominal GPS receiver C/N0 values often are in the 40 to 50-dB-Hz range.

Edited by - poppap on 19 oct. 2008 03:04:23
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tsmccull

21 Posts

Posted - 19 oct. 2008 :  05:07:28  Show Profile  Reply with Quote
Yep, that's it. Just hold the elevation selection for a few seconds and those screens pop up.
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gpspassion

94636 Posts

Posted - 19 oct. 2008 :  12:30:20  Show Profile  Visit gpspassion's Homepage  Reply with Quote
This is a very interesting screen indeed, espeically the "Eph" column, I wonder if it would show whether the HotFix AGPS "synthetic ephemeris" have been calculated and are available, or only the "live ephemeris", if you're not familiar with HotFix APGS, you can read about it here : http://www.gpspassion.com/FORUMSEN/topic.asp?TOPIC_ID=102346 and http://www.gpspassion.com/forumsen/topic.asp?TOPIC_ID=104294

A "Warm Start" is what you get when you get started in the morning, the GPS knows where it was switched off and has "coarse" time, so it's the best TTFF test IMHO. Wonder what "Prdc Wrm St" stands for though, maybe without AGPS data.

By the way I tried the trick on the 255 and 860 but no go.

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poppap

89 Posts

Posted - 19 oct. 2008 :  12:55:37  Show Profile  Reply with Quote
seems like only available in 7xx series...
I think "Eph" only show live ephemeris..

"Prdc" may be "Prediction"?

Edited by - poppap on 19 oct. 2008 12:58:22
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gpspassion

94636 Posts

Posted - 19 oct. 2008 :  13:22:14  Show Profile  Visit gpspassion's Homepage  Reply with Quote
Ah that could be it, do a warm start with predicted/synthetic ephemeris. I will leave my 760 on for 24 hours so it can build synthetic data.

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poppap

89 Posts

Posted - 19 oct. 2008 :  15:07:58  Show Profile  Reply with Quote
I now think that "Prdc" stands for "Periodic" because it keep restarting warm start after it got the fix.
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SergZak

USA
1815 Posts

Posted - 19 oct. 2008 :  21:26:58  Show Profile  Reply with Quote
Two questions:

1. What firmware version is this working on? 4.2? I am on 3.1 & 3.2 on two different units and this does not seem to work with firmware v3.x

2. Exactly how long are you pressing/holding the elevation data section to get to this screen? 10 seconds? 1 minute?

nüvi 3490LMT, nüvi 3790LMT, nüvi 765T, nüvi 855, nüvi 760, nüvi 750
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danham

USA
7492 Posts

Posted - 19 oct. 2008 :  22:23:12  Show Profile  Visit danham's Homepage  Reply with Quote
With 4.2 on my 760 it takes about 4 seconds for the SNR screen to appear.

-dan

- Nüvi forum moderator -
Nüvi 760 in a '14 VW GTI & zumo 660 on a BMW F800 ST
Guide to working with pre-programmed routes: >> details <<
Language Guide / US Topo / 350 & 680 / MacBook & Intel iMac with OS X & Win XP / BaseCamp / Cape Cod, MA
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SergZak

USA
1815 Posts

Posted - 19 oct. 2008 :  22:40:18  Show Profile  Reply with Quote
Thanks Dan. Seems as though this is a 4.x firmware feature since I simply cannot access it on my 3.x units...and I'm not ready to update to 4.2 any time soon either.

nüvi 3490LMT, nüvi 3790LMT, nüvi 765T, nüvi 855, nüvi 760, nüvi 750
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guggie

141 Posts

Posted - 20 oct. 2008 :  00:35:50  Show Profile  Visit guggie's Homepage  Reply with Quote
Not on my Nuvi 760 either, at version 2.x

Connecticut, USA
Garmin 760, aviation model GPS 90, and ETrex Vista HCx
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poppap

89 Posts

Posted - 20 oct. 2008 :  09:06:04  Show Profile  Reply with Quote
I just notice that it create the file in the root of nuvi flash drive.. here is the sample..

I believe the format is
C/N0...,Accuracy,Lat,Lon,Elevation


edited: It's too long and changed the screen layout so I posted it here instead.
http://pastebin.com/f4686ddd3


my location was changed to xx.xxx and yy.yyy but you get the idea...
it doesn't seems to record the timestamp else we can use it as an exact tracklog recorder...

Edited by - poppap on 20 oct. 2008 10:03:56
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tsmccull

21 Posts

Posted - 20 oct. 2008 :  17:56:26  Show Profile  Reply with Quote
That's interesting. Since this seems to be a newly added function, I assume that Garmin has some future plan to make use of the data file. Given all the issues that have surfaced with the last several SW releases, it just seems counterproductive to add an additional capability to the system which is bound to take away some of those precious computer cycles while the programmers are trying to speed things up!
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poppap

89 Posts

Posted - 20 oct. 2008 :  22:41:54  Show Profile  Reply with Quote
Well.. it only create the file when you click "Start log" so I think it's for debugging purpose... don't know if it'll lead to any new functions..
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