Re: GPS - Can't get a fix
 

You may find this advice extracted from http://fragostech.com/MaemoMapper/ helpful.

Failure to Lock Troubleshooting

The GPS driver writes a almanac /var/lib/gps/nvd_data which it uses in subsequent times when the driver is started. Almanac contains orbit information on all satellites, clock corrections, and atmospheric delay parameters. It is transmitted by a GPS satellite to a GPS receiver, where it facilitates rapid satellite vehicle acquisition within GPS receivers. It appears that if the N810 is powered down during this write the almanac will be corrupted. As a result it is recommended that after terminating Maemo Mapper during a session with a successful lock you save an almanac copy for backup purposes. Open a terminal window and run:
cp /var/lib/gps/nvd_data /var/lib/gps/nvd_data.bak

If there come a time when the GPS lock won't occur even considerably past a half hour, the saved almanac should be restored. First terminate Maemo Mapper and then open a terminal window and run:
cp /var/lib/gps/nvd_data.bak /var/lib/gps/nvd_data

You will have to restart the GPS by opening the N810 Control Panel, tap GPS location, uncheck Enable GPS and tap the OK button. Lastly tap GPS location again, check Enable GPS and tap OK. When restarting your restored nvd_data almanac will be used.

This may not be a cure all but has been reported to restore correct operation in a number of instances. Hopefully this issue will be fixed or accommodated in the GPS driver.

Re: GPS - Can't get a fix
 

This theory would imply many people have a GPS hardware malfunction. You do have 3 years of warranty in EU.

Re: GPS - Can't get a fix
 

I'm beginning to wonder what role an Internet connection plays in getting the initial fix. I've installed and run agps some weeks ago. Just now my N810 was in off line mode and I started Maemo Mapper. It found no satellites so I reset the GPS by disabling and then enabling. Still no satellites. Next I put the tablet in online mode and established a WiFi connection. Again I reset the GPS and now I have satellites in view and acquired a fix within a minute or two. Is this a coincidence or have I discovered a solution? More experimentation is in order. Comments anyone.

Re: GPS - Can't get a fix
 

What you describe is exactly what I would have expected: With A-GPS on it can help only if you have active internet connection. Without internet connection A-GPS can not pull visible satellites data from the internet. Once you opened internet connection and activated GPS, A-GPS downloaded visible satellites data from internet and got fix faster.

However, even without internet connection the tablet should find satellites after some time (minutes...) and get fix after all. If you did have your tablet looking for satellites say ~3 minutes and still didn't have a single satellite, that isn't normal.

Re: GPS - Can't get a fix
 

For some reason I'd thought that agps built a list of sites when it was 1st run and continued to use that list until directly run again. It would appear that I'm mistaken on that point and need to update my Maemo Mapper HowTo which discusses and recommends the use of agps.

Re: GPS - Can't get a fix
 

fragos:

You may find these links helpful:
http://www.nokia.com/betalabs/agps-tablet
http://betalabs.nokia.com/blog/2008/...n810/#comments

EDIT: I saw that you have already posted comments there... So no news for you? :o

Re: GPS - Can't get a fix
 

Hmm, after installing minigpsd, Maemo Mapper can't find the (internal) GPS anymore.. :(

Re: GPS - Can't get a fix
 

Just to avoid confusion about almanacs and ephemeris data.

nvd_data probably contains both the almanac and ephemerides actually. The almanac gives the long term (6 week iirc) rough orbital predictions for all the satellites and the ephemerides give the short term (30min?) corrections to account for a variety of things including atmospheric disturbances (on a per satellite basis, and just for those in view).

See here for example: http://gpsinformation.net/main/almanac.txt

Re: GPS - Can't get a fix
 

Hmm, by turning off GPS and turning it on again, the (wayfinder) map application finds the GPS, and so does Maemo Mapper. But despite using AGPS, maemo mapper only shows 1 satellite in view (strength 33), 0 in use - and if i quit the wayfinder map app, Maemo Mapper looses the GPS, so somehow gpsd/minigpsd gets killed.

Re: GPS - Can't get a fix
 

Yesterday I did some more experiments with the N810 GPS.

For testing I did try to get a fix in my house downstairs. In that location it is normally impossible to get a fix, but I just wanted to see what signal strength MaemoMapper GPS details show. After about 10 minutes of wait I had signal from 3 satellites. The strongest was about "30". I did not get a fix. (All this with A-GPS enabled.)

I moved upstairs where the signal strength is better. My strongest signal improved to about "33-35". After this GPS started to find more satellites, and finally got a fix in about 3 minutes.

Once the GPS has fix the satellite signal strength bars are updated much more frequently, maybe about once per second. I experiment how much holding tablet in hand in different positions affects signal strength. I did find some surpising results:

1) In general holding tablet on hand anywhere else than upper left corner increased signal strength significantly (up to "10"...) This appear to be due to "grounding" the tablet chassis.

2) Holding hand above (close but not touching) the tablet upper left corner significantly increased signal strength on some satellites. Some in excess of "10"! It appear that the most gain was with satellites where hand was exactly placed between satellite and N810 GPS antenna (located at upper left corner?)

3) Combining 1) and 2) doesn't seem to bring any more gain.

These are my basic findings... Especially the 2) surprised me a lot. The only explanation (?) I can think is that the hand will form an antenna element (similar to the "sticks" in front of the yagi/dipole antenna) to increase antenna gain. Now you guys with more experience in RF and antenna theory can chime in... :rolleyes:

Re: GPS - Can't get a fix
 

I can confirm your observations - once I finally got a fix again, the satellite status is almost realtime instead of "once every now and then", and holding my hand over the unit or holding the unit from below does increase the signal strength.

Re: GPS - Can't get a fix
 

Good news, i just got my n810, it was an open box/display model via ebay. This morning I used the Wayfinder app for the first time, and it locked and tracked within seconds. I didn't do anything before hand. I did install the agps app and installed maemo maps but hadn't run either one. This was strictly Wayfinder app. I also didn't have a web connection at the time either. I live in a moderately hilly area, with pretty large amount of tall trees lining the roads I take to work.

Anyway, I'm wondering if this has been fixed in earlier models of the n810? I'm sure my luck will be different this afternoon. I'll give it a shot when I leave work and see how it does.

Re: GPS - Can't get a fix
 

I found an application that as well as adjusting the N810 clock to GPS time, logs the time to get a fix. Add the folllowing repiository:

Catalog name: Nitapps Maemo Repository
Web address: http://nitapps.com
Components: user

You'll now be able to install gps-clockd. Once installed it will automatically run whenever the GPS is used. You can view the log in the Terminal as follows:

~ $ cat /var/log/gps-clockd.log
[Mon Nov 3 12:26:41 2008] *** GPS Clock Daemon started ***
[Mon Nov 3 12:29:35 2008] GPS activated. Time to first fix 02m17s
[Mon Nov 3 12:29:30 2008] Adjusted clock by -5.08 seconds to match GPS time
~ $

Re: GPS - Can't get a fix
 

good news, after i got out of hte parking deck after work tonight, and got to clear sky (basically right outside of the parking deck) i had a lock in as little as 45 seconds. this is using day of my wayfinder trial.

so i wish i could tell when my n810 was made so we could see if its a hardware thing that has since then been fixed

Re: GPS - Can't get a fix
 

Did you find any difference with this apps before and after install, or no difference, on the gps lock time?

bun

Re: GPS - Can't get a fix
 

My N810 also has a totally ******ed gps. Naturally, I have tried almost all suggestions in the forum. None of them work consistently. The best, I found, so far to get a lock, is DONT MOVE, stand still, it gets lock faster than any tricks. face south, face north, stick it in your mouth, or say a little prayer, whatever, none of them work for me. I, usually, leave it in the car, go take a 'leak', it locked when I came back, under 5 minutes. If it does not lock, I would reboot, I think it is confuse :-]


bun

Re: GPS - Can't get a fix
 

This ap made no difference in lock time and wasn't intended to. It does give us a more scientific measurement of time to fix. I've spent a lot of time researching this issue and rather than reitterating what I've already documented check out the Maemo Mapper HowTo http://FragosTech.com/MaemoMapper. It has a lot of information on what impacts getting a fix and what works best.

Re: GPS - Can't get a fix
 

Thanks. That is a lot of work!

bun

Re: GPS - Can't get a fix
 

thanks fragos, you definitely put a lot of work into this and its appreciated. just to give another update..

i'm on day 2 of my wayfinder trial with my new (used) n810 and it got a lock in 101 seconds. while i'm thankful I haven't (knock on wood) had any TTF issues, I would like to know what the difference is for me versus the large number of users that do have TTF issues.

i'm going to spend some time reading through your site tonight fragos to see if i can't make some sense of it.

have you used that mapping app that lets you use garmin maps? or is that maemo mapper? :)

anyway thanks again. i just wish the n810 was faster. oh well, for what it is, it seems to be a great solution.

Re: GPS - Can't get a fix
 

all week I've been able to get a decent fix.
This morning no matter what I did it just wouldn't lock.
We drove around for hours chasing this one sole patch of clear blue sky but to no avail.

Make sure there is clear line of sight when trying to get a lock.
Obviously, this means it must be daytime else the n810 won't see the satellite.

Re: GPS - Can't get a fix
 

LOL I just had the most pathetic thought.

5 PM, ding dong, John Nitwit leaves the building, kindly on a raisin hunting job on request by his wife.

8 PM, John is lost in the cloudy dark.

11 PM, John arrives home, exhausted. "Where have you been", his wife asks. Answer: "It was cloudy"

Anybody up for a comic? :D

Re: GPS - Can't get a fix
 

Very frustrated with the GPS on the N810. Cannot get a fix no matter what, sticked out to the window, rebooted, turn on a-gps, turn off a-gps, follow the sun, sticked into my mouth, pointed to south,........... fiddling for over 30 minutes, finally we got to the destination, well, one has to stop a car to get out, right? Once the car stopped, it fixed.

I have many BT GPS, 4 of them. I also have many N800, 2 in my possession in the house. I also has a dedicated standalone GPS and a cellphone with google map installed. "Dont bother, honey, I will just take the N810 and save a lot of trouble in carrying all those gadgets.............." That was what I thought. We got lost in a new city for 30 min till we got to where we want to go!

The bottomline, an unreliable instrument is more damaging then NO instrument.

I carefully put my N810 into my drawer, gave it one last glance, albeit a sad one............and now I resume carrying my N800 around.
Dont know whether I should put the N810 to ebay or wait for a fix.

A very upset former N810 user,

bun

Re: GPS - Can't get a fix
 

This always works for me:
Connect to my wifi, start maemo mapper, wait till it downloads and shows all satellites (about 1 minute), go outside to an more or less open area (far from metal buildings to avoid reflections) while I walk to the garage, wait to get fix watching the satellite signal bars, if 3 bars don't go above 30 move a bit. Usually I get a fix in 1 minute.

Re: GPS - Can't get a fix
 

GPS fixes come faster with the N810 if you have an active Internet connection. The N810 will work with an external BT GPS that you already have.

Re: GPS - Can't get a fix
 

I have active BT internet connection during the whole ordeal. The tablet is tethered to my cell... I just wish I had brought along my BT GPS, as allnameswereout put it, the ONLY solution currently available. The problem is well documented, either Nokia CANNOT fix it (a recall?) or Nokia does NOT want to fix it (model discontinued?)

bun

Re: GPS - Can't get a fix
 

But, after you load maemo-mapper and the gps becomes active, does it show all 10-12 satellites in the gps info panel?
If they show, but you get low signal bars, then it is a hardware problem.
If they do not show, then your internet connection is not working as it should (it can't download the ephemerids).

Re: GPS - Can't get a fix
 

After load maemo-mapper, no, it does NOT show any satellites. It takes a long time to catch a few, and then they all disappear, and it then re-start to catch a few, and it disappear again, it keeps on going, but just cant fix.

I am very curious to hear how you point the finger to hardware problem. I am thinking to get it return.

If they do not show, then it is internet connection problem? I think I do not get that. I can browse thru web pages, then suggest internet connection is fine.

I really want to point finger to hardware, although not sure how. And as it happened million times, just when I thought it is hardware, never get a fix, it fixed when I am NOT moving. But man, that is more than 30 min to an hour, sometimes.


bun

Re: GPS - Can't get a fix
 

Don't buy the N810 for the GPS. There are many reasons why its a nice device; why it is preferred over N800. But the GPS isn't one of these reasons. External BlueTooth GPS are cheap these days.

Re: GPS - Can't get a fix
 

Even if you can browse web pages, that doesn't mean that you aren't blocked from the ephemerids server, by a firewall problem for example, or that agps is not working.
Try using a wifi connection. It doesn't matter if you are inside a building and get no signal, after opening maemo-mapper with a working internet connection, it should download the satellite ephemeris in less than a minute and show about 10 satellites in the info pannel. If that doesn't happen, you have a problem there.
The n810 saves the ephemeris in the file /var/lib/gps/nvd_data, if that file becomes corrupted for whatever reason, you won't get a fix even after 30 mins.
First, delete that file and restart the tablet (shut it down and drop the battery to make a hard reset), then set the clock using ntpdate or rdate (the clock is important to get a quick fix), then connect to internet (using wifi if you can), and start maemo-mapper, then the satellites should appear in the info panel.
If they still do not appear, there is a software problem somewhere (corrupted filesystem maybe, or your internet connection).
If they appear, you can close maemo-mapper and the internet connection if you wish (the data is valid for 30 min); go outside (try to choose a place where you can see as much of the sky as you can), and start maemo-mapper, the same satellites will appear in the info panel, and you should get a fix in about 1-2 min.
If the satellites are in the info panel, but you can't get a fix (the signal bars are small), probably it is a hardware problem.
To check the signal strength go to maemo-mapper menu->gps->details->satellites details. To get a fix at least one satellite should be over 30.

Re: GPS - Can't get a fix
 

I also have very long time to have a fix with Memo Mapper and a-gps with wi-fi connection. It shows a continuous message
Searching for a GPS receiver
the GPS icon disappears, appears again cyclically and nothing happens.
But
if I launch first Wayfinder it get the satellites signal very fast. Then I launch Maemo Mapper and voilá I have almost instantaneously a fix.
What is wrong with my setup, please?

Re: GPS - Can't get a fix
 

Just because of you, I went into the trouble of digging out my dusted N810. I plugged in, connected wifi, fired up maemo mapper, satellite in view:7 in use:0 , slowly, it started to populated, voila after 5 min 33s, it locked! It fixed, inside a building, with wifi. I disconnected the gps and reconnected it, it took about 20s to get the GPS display back, and it then started to populate the satellite and it all disappeared, and not even one satellite in view, its been 10 min, nothing happened, not even one bar of satellite, I am still waiting.... usually, sometime later, it will lock again. As I keep re-iterate, it locked only if I stay still.

Regarding the clock thing, I use gpsclock and I noticed that it kept on correcting, albeit .5 s or 1 s, a small number, but why it requires constant correction? It has been 22 mins, and no fix and only 2 satellite bars in sight. I am inside a building and I am NOT moving.

It has been 30 min....no luck, if I depends on this thing to go somewhere, I do not think I can hold my temper down.

I have 3 BT gps, 2 new ones and one really really old one. The 2 BT gps lock in seconds, everytime, everywhere, I have never had ant bad experience with them. The really really old one, takes about 4-5 min to get a lock, it takes awhile, but it will lock. I can depend on it to get a lock after 5 min. Not the N810.

Still cant get it fix, its been 42 min, n810/4.2008.30-2

I rebooted the whole thing..., and now the sat bars slowly repopulate, well, I have spent enough time on this thing. It did not work and I run out of energy. Thanks,

bun

Re: GPS - Can't get a fix
 

I also notice start up wayfinder first has better luck to get a lock then MM 1st. That was history anyway,... I am more happy now as I do not have to worry whether the N810 is going to catch. I am using an N800 with BT gps and it is fine.

bun

Re: GPS - Can't get a fix
 

OMG, it locked. after another fresh reboot!
The N810 fixed with the satellite.

Cant get a fix after 40+ min, I rebooted, and just left it there, TIme to first fix 12m26s after a fresh reboot. Really, the gps on the N810 is a joke.

bun

Re: GPS - Can't get a fix
 

Hard to say, but it seems there is some configuration problem, and maemo-mapper is not able to start the gps, maybe some file is corrupted.
You could try uninstalling maemo-mapper, doing a hard restart (shutdown+drop battery), and reinstalling maemo-mapper.

Re: GPS - Can't get a fix
 

Did you deleted /var/lib/gps/nvd_data before restarting?
If you did, then it seems a hardware problem. Is it still under warranty?

The gps satellite data varies because atmosferic distortions, so that is the cause of the small time variations.

About getting a fix inside a building, the n810 usually can't. Outside buildings it should work fine (as long as you have recent ephemeris).
As I said, after I have populated the satellite data using internet, I get a fix in less than 3 minutes on the street, even moving.

Re: GPS - Can't get a fix
 

Why is it always a hardware problem which requires warranty? There must be many people who have a hardware problem with the GPS chip. Even new devices. Has anyone ever experienced the GPS working well for a while, and then suddenly not anymore? If you send it you're wasting time and money on something which might not even be broken. Face it, the thing sucks, it isn't worth it to tinker about. Just use a good external GPS device instead.

Re: GPS - Can't get a fix
 

I tried to reconcile with a hardware problem. They sold thousands and thousands of N810, just a guess, and the people complainted about it, less than 100s, again, another guess. So, if the maths is correct, thousands thousands minus 100s, there got to be 999000s satisified customers. Tell me I am BS, again :)

bun

Re: GPS - Can't get a fix
 

No. I did not. Maacruz, thank you very much for you trying to help. Usually I am much upbeat than this. But after trying millions of different ways, and updated to Diablo etc, and over a course of 10 month, I am just tire.

bun

Re: GPS - Can't get a fix
 

The latest version of A-GPS has a new menu fuction "Info" which will tell you if nvd_data is valid or corrupted. My GPS had been working well but this AM failed. A-GPS told me it was corrupt when I ran it. Following maacruz's directions I deleted nav_data, powered down and pulled the battery. With an Internet connection I did get a GPS fix in a reasonable time. Just one note: nav_data won't be written until Maemo-Mapper is terminated. There may be a message here. nav_data may become corrupted if you exit MM without an active GPS fix -- purely a guess on my part. At least A-GPS can now tell us if nav_data is OK.

Re: GPS - Can't get a fix
 

I just checked it, yes the N810, a-gps info, cache refreshed: Nov 11...2008. Cached data is valid

OK

well, no cigar :(

bun