Problems Finding Satellites

[dwgsp]

I used my new 140S on a trip last week, and noticed that it sometimes had trouble finding satellites. A typical scenario would be that I would turn off the unit when I stopped for lunch, then turned it back on when I returned to my car to continue the trip. Usually the 140S would find the satellites almost immediately, but in one case it took almost ten minutes (and a couple power off/on cycles) for it to find them. This was on the open road, with a clear view of the sky. This behavior is quite annoying.

I have owned other brands of GPS devices, and the 140S is the first that has behaved like this. Is this normal behavior for TomTom devices?

Thanks!
/Don

 

[dhn]

Not normal, no, but it happens.........

Have you gotten a gpdquickfix file update lately? Also, a reset on the unit sometimes helps.

 

[dwgsp]

Thanks for the reply. I loaded a gspquickfix the previous day, but in this case I don't think that matters. The gps satellites broadcast ephemeris data that is equivalent to a gpsquickfix every thirty seconds. Since my device had been on and tracking for a couple hours, it definitely had the most current satellite data.

If the problem continues to occur, I'll try the reset.

/Don

 

[CynicX]

I cant help from notice a few of these threads popping up.

Yesterday from 12pm to 5pm EST, I had terrible reception. The reception started off great in the morning but around lunch time was dropping off. I leave the GPS on all day so it wasnt because I was moving around with it off. So it was unusual...could have happened at a worse time, I was in a new very very busy town/city (no skyscrapers or even tall buildings for that matter)...

I reset the unit and even cleaned the windshield. Nothing helped. Around 4pm it went from 2 bars to 3, at 430pm it went from 3 bars to 4, and at 5 I had full strength (but only 6 satellites). By the time I got home I had around 10 satellites and it was working flawlessly again.

I dont know if it had something to do with a quickgpsfix error, or even the prediction of degrading satellite signals...hehehe. Anyway I'm curious if this was more of a wide spread issue. Regardless today it worked great with good signal all day, and I was even in the same area as yesterday...

Seems like some of these post have been coming from the east coast, I'm in Maryland, the OP is in NY and there is another one in Maine. Maybe its just a coincidence though...

 

[SteveClark1000]

I also had problems when visiting Long Island. It took one or two minutes to find a satellite. No problems before or after my trip here in Phoenix, AZ.

 

[dwgsp]

A quickgpsfix error would not cause the reception problem that CynicX reports. The data that quickgpsfix installs simply updates the information that the gps receiver uses to initially look for satellites when you turn on the receiver. The orbits of the gps satellites change over time, so the quickgpsfix data may help the receiver to initially find satellites when power is turned on, allowing it to determine it's initial position more quickly.

The gps satellites themselves broadcast this information (it's called ephemeris data) approximately every thirty seconds, so a short time after the receiver is powered on it will have the latest satellite information, independent of quickgpsfix. This will then be continueously updated as long as the receiver is powered on.

Quickgpsfix data is probably most useful in situations where the gps receiver has not been used for many days. Most gps receivers, when powered off, save a copy of the last set of ephemeris data that was received from the satellites. I assume that TomTom follows this practice. So if you use your gps receiver on a regular basis the receiver will already have a pretty accurate set of ephemeris data.

/Don

 

[imabiggles]

A quickgpsfix error would not cause the reception problem that CynicX reports. . .

It certainly can and did on mine. I had an issue with super long lock times, crap signal, and hours were my xl would not lock at all. I loaded home up and checked for updates, none showed. I looked in the quick fix location on my tomtom (epher-somethingorother) and it was blank yet home did not show a quick fix available. I went to install the quickfix I had downloaded on the pc through home before and it installed on now shows up on my tomtom as an installed file. Took it back outside and boom - signal maxed and I have 10 sat locks where before I had three at best of times. All I did was the quick fix, so it does resolved some 'cant get a lock, takes forever to lock' issues.

 

[gatorguy]

And a bad quickfix update can certainly cause sat lock delays even for daily users. It doesn't happen often, but does appear about every 3 or 4 months it seems.

 

[mikealder]

I fail to see why the qGPS data is even needed, use the device on a regular basis and it serves no purpose, I haven't used it on any of my units that support it for quite some time (years not months or weeks) and I get a position fix in under 30 seconds, quite often in less than 10 seconds isn't unusual, why run the risk of duff data corupting the positional accuracy - Mike

 

[doctormstein1]

gps fix

just wanted to add my two cents that maybe once a month I get a longer gps fix on my 920. But 99% of the time it comes on very fast. That one percent of the time is sometimes agravating when you want to start your trip. You really have to chaulk this off to the satalites. My friends that have a garmin unit also have this same problem. On the whole however, tomtom is wonderful.

 

[dwgsp]

I can see how a bad quickgpsfix would cause slow satellite lock the next time that you power on the gps device, but once the ephemeris data has been received from the satellites you should be good to go. Perhaps there is a bug in the TomTom software.

/Don

 

[CynicX]

I see what you are saying. If I had a bad gpsfix it would have initially taken a long time, or even given me problems for awhile. However I HAD a good signal then all of a sudden lost it, had terrible reception all day, then toward the end of the day it came back to normal...

I usually plug it in every day for the latest mapshare updates. Therefore I've been resetting it everyday, and its been working flawlessly.

I'm curious to see how it works if I dont update/reset it for a few days/weeks. Keep in mind I usually navigate to about 4-6 locations I've never been too 6 days a week, about 8-10 hours a day. So this thing sees a TON of use...

 

[mvl]

I fail to see why the qGPS data is even needed, use the device on a regular basis and it serves no purpose, I haven't used it on any of my units that support it for quite some time (years not months or weeks) and I get a position fix in under 30 seconds, quite often in less than 10 seconds isn't unusual, why run the risk of duff data corupting the positional accuracy - Mike

My understanding is that the satellite-broadcasted ephemeris is only good for a few hours. If you turn your Tomtom back on within those few hours, you reacquire signal in 10-30 seconds.

I'm not sure what a "few hours" is, but it certainly is less than an 8-hour work day. My experience is that without quickgpsfix, the signal lock takes about 3-5 minutes on average if the device has been off for a few hours.

Now that I have a bluetooth connection, I enable autoquickgps fix. It downloads the file via bluetooth without having to plug into a computer, and I always have 5-10-second locks (except when Tomtom has a bad file)

FYI - The bad quickgpsfix file released recently appears to affect only models with the Hammerhead GPS. Hammerhead is used on most (not all) ONE/XL models. The SIRF chip used on most GO models was not affected this week.

 

[gatorguy]

MVL, is the "bad quickfix update" you refer to the one from 3 weeks ago, or has another flawed one been offered since?

 

[mvl]

It appears the hammerhead models got a bad quickgpsfix a couple of days ago. I've seen many posts on this forum reporting problems connecting to satellites. All one/xl, no GO models.

This is different from the bad sirf quickgpsfix a few weeks ago.

 

[gatorguy]

Just my opinion, but I don't think just a flawed quickfix file would cause intermittant sat lock. Many of the complaints aren't about initial satellite reception. Instead reception is being affected during use.

 

[mvl]

It's quite possible that an east cost satellite is misbehaving. However, if this was the case, I would expect to see both the SIRF (GO) and Hammerhead (ONE/XL) chips reporting issues. Still haven't seen a GO owner report issues.

Well, now that I think of it, I saw 4 bars on my GO every now and then over the past few days, it normally has 5 bars. Maybe there is a satellite issue and the SIRF chip is powerful enough to overcome it.

 

[gatorguy]

Certainly possible. Some of the complaints just aren't typical of a bad quickfix update. Call me gun-shy, but there's been too many satellite reception related problems from different chip sources lately. Just makes me suspicious anymore.

 

[CynicX]

I read a while back that the pentagons latest satellite launch was equipped with new tech for new civilian frequency called "L5". Going to be used for, air traffic control or something like that. Anyway this new frequency was interfering with normal signals from the satellite making them less accurate, 10 fold if I remember correctly....

I wonder if that has something to do with it? I also read a lot of stuff on the of a "magnetic anomaly" on the east coast of South America. It was technical article and above my had but it was mentioned that Hubble was shut down while passing through this area to prevent damage.

So much information and its hard to tell whats true or not...

EDIT :

GPS Satellite Glitches Fuel Concern on Next Generation - WSJ.com

That is the article I read. About the Locheed Martin satellite interference....

 

[dhn]

In Britain, the Department of Defence (I think it is) has regular gps satellite signal jamming exercises. They announce ahead of time the location in the British Isles that might be affected, the date and the hours.