GPS Question: Garmin Nuevi

Factual Questions
1

A couple of years ago, for my cross-country bike ride, I bought one of these GPS systems to help us find our way.

About a week ago I dug it out (we’re still unpacking here), and decided to hook it up to the Desk Top and update the maps, and, as far as I knew, everything loaded just fine.

Today we needed it for me to go to a doctor’s exam, so I loaded the address, and I got the “Searching for Satellites” message and it stayed on for about 10 minutes.

Okay. No big deal. It’ll find a sat in a bit, but we went 10 miles with the unit still “looking”.

(I know about the troubleshootng tip to hold it where there aren’t any tall buildings and trees, btw)

Luckily, I was able to do a google map on my wife’s cell phone, but then whatcha think happened?

We got within 500 yards of our destination and finally “Dr. Nightmare” announces: “Go .5 miles and end at this dreadful destination” (or something like that).

Well, thanks a lot, “Doc”!:rolleyes:

I called my bro’ who brokers truck loads and knows about such things as GPS, and said “it must be a software glitch, Bill”.

I told him it was very cloudy in Georgia today, and maybe that’s the reason, it wouldn’t pick up a sat, but he said no, that shouldn’t make a diff.

So I come to the all-knowing Dope.

What say you, O Wise Ones?

Thanks

Quasi

2

If a GPS unit hasn’t been used for a long time (like a year or so) then it will take a long time to get a lock. I’m not sure on the exact reasons, but I think it has to do with having to download new ephemeris tables etc etc.

It’s the same when you switch it off, then move a few hundred miles before turning it back on. They have to get temselves sorted. Next time you fire it up it should be a lot quicker.

3

So let’s take him on a “short ride”, Col’? To get him re-calibrated?

My doc appointment today was 50 miles away, and, as I said, he finally jumped in when were almost there.

I really love it when he says “Looks lahk the satellites have been scared aoufff!”

Doesn’t take much to amuse me these days! :smiley:

Q

4

It’s not necessarily just a long time thing… Mine does that anytime I turn it on in a different location then where it last was shut off. Longest it ever took was in London… but there is a setting on my Nuvi that comes on eventually that asks if you’re more then 200 miles away from the last spot. I hit yes, even if it’s less then that, and then it attempts to search (for what I think) is a bigger list of sats.

5

Hmmmm. Mine just asks if I want it to continue searching?

I’ll go to the Garmin site and see about downloading those tables.

I suspect those guys have good tech support.

Thanks for the help!

Q

6

Hey

I just wanted to add that I took the Nuevi out, held it still, let it seek out a sat, and haven’t had a problem since then.

Sometimes ya just gotta trust the directions, ah reckon! :slight_smile:

Thanks for all the help!

Quasi

7

I take my Garmin with me when I travel by air (packed and checked, of course).

When I unpack it and set it up in the rental car, it typically takes at least a minute or two to find the satellites now that it’s hundreds of miles from where it used to be. Same thing when I return home.

8

Why packed and checked? I wouldn’t pack anything that I wouldn’t want to disappear. I use mine on board (after I double checked that it was allowed) and it’s really interesting to see the speed at 500 MPH. :slight_smile:

9

What does the display screen show when you’re flying? What is your position relative to roads?

10

Up. :slight_smile:

I’ve used my Nüvi on board a plane, too. If you have the map zoomed in, it tries to jump to roads as you fly over them, but at that scale it has trouble keeping up with the speed. If you zoom out quite a bit, though, with the map in the “always north up” mode, you get a neat little arrow showing your position, just like the displays they sometimes have on screens in aircraft when the movie’s not showing.

It’s quite useful for identifying places you can see out of the window.

11

How are new ephemeris tables useful to a GPS?

We have a Nüvi 750. On average, it takes about ten minutes to find a signal. We’re in wooded downstate New York, but nothing egregious. There’s even a five minute or so jaunt on the highway with no trees near.

Would an external antenna help?

12

I mentioned ephemeris tables, it was a bit of a vague recollection. As I understand it, if the GPS unit has been used recently in the same location, the satellite configuration is still pretty close to what it “remembers” so it should pick them up again quickly. But if you travel a long way or leave it a long time before switching it on after a period of inactivity, it basically has to search from scratch again.

My Nüvi typically gets a lock within 30 seconds or so - maybe 2 minutes if I’ve moved to a distant location. I don’t know why yours should take so long. One possible idea - do you have a heated windscreen? The metal heating elements can block GPS signals pretty effectively.

13

GPS uses ephemeris tables to get an approximate location of the satellites. It needs to do that before using the radio signals to figure the exact positions.

14

On my Nuvi 350 , if you want to avoid it jumping to roads -
Main Menu screen : Settings : Navigation : Route Preference : Off Road

For hike in the woods -
Main Menu screen : Settings : Navigation : Vehicle : Pedestrian, plus having done the Off Road bit above.

15

A greater concern to me than the length of time it takes it to find satellite signals is that the cost of updating the maps is very nearly what I paid for the thing.

16

I’ve never bothered updating the maps. I mean, really, how many roads actually change that much? I get an occasional and fairly discreet nag screen when I switch on, but it’s easy to ignore.