No Fix on cloudy day?

goflyintad · 05-20-04, 03:14 PM

It's my second day using gps on 3xi. I tested my 303E yesterday within a minute or two, I recieved good signals but didn't stay around long enough to get a fix. Today, with my available time, I decided to give my gps a good test. I set it up and wait for a fix. I waited for 30 minutes and I still doesn't get a fix. What's wrong with this picture? Yesterday was a clear day and today is a cloudy day? Does the weather affect the gps?

balloonchasers · 05-20-04, 03:45 PM

goflyintad,

I have a stand alone gps unit (magellan gold, used for geocahing) and have never seen clouds have an affect on gps signal. There has been some discussion that a heavy snow storm may affect the signal. I have only used my gps once during a heavy snow and I could not see any dramatic decrease in the signal strength. A few simple questions: Were you inside a building when trying to get your fix? Under tree cover? These can decrease the signal by a large amount. Even certain car windows have a special treatment which can affect the signal. Just a few ideas.

tgreenstein · 05-20-04, 04:33 PM

The initial fix can often take quite a while -- you may not have waited long enough. Remember, the unit has no idea where on the planet you're located, so it can take some time to get that first fix. After that initial fix, the GPS unit has some information to go on which makes subsequent fixes much faster.

And no, cloud cover shouldn't have much (if any) effect on your satellite reception.

HarishKM · 05-20-04, 09:54 PM

Does it mean that the GPS receiver has some sort of non erasable memory which retains info even when power is off or after the initial fix, this info is stored on the PDA?

Pl. enlighten.

spoon · 05-20-04, 10:59 PM

Clouds do not affect my GPS on the X5 - remember one thing - once you do get a fix like tggreenstein says it may take awhile - you need to make sure you use it every now and again to retain the warm fixes in the future - the 1 st cold fix can take awhile but subsequent fixes will be quick but it can loose it`s bearings if not used for awhile and you will need to resort back to a cold fix.

tgreenstein · 05-21-04, 07:32 AM

Quote:

Originally posted by HarishKM
Does it mean that the GPS receiver has some sort of non erasable memory which retains info even when power is off or after the initial fix, this info is stored on the PDA?

GPS receivers typically have a small battery (usually Lithium-ion) that allows onboard memory to retain the coordinates of the last position fix, even if the GPS unit is not attached to a PDA. The memory is not "non-erasable", though; it can usually be reset by a small utility program (usually provided by the manufacturer).

igurevich38 · 05-21-04, 03:14 PM

Were you moving or standing? If you havetrouble getting a fix while standing you should try moving, it usually works right away.

Was the GPS located in your car? May be you put it too low and the roof was blocking it.

Where are you located physically? There are some place in the US where the government may block the signal sometimes for military purposes.

303E should never take 30 min to get a lock. 5 min at most, but usually no more than 1.

tgreenstein · 05-21-04, 06:34 PM

Quote:

Originally posted by igurevich38
303E should never take 30 min to get a lock. 5 min at most, but usually no more than 1.

I think goflyintad was talking about the inital (first) fix. After that, one minute is reasonable (assuming that you have a good unobstructed view of the sky, that the current location is reasonably close to the previous fix, and that you have a stationary receiver).

igurevich38 · 05-23-04, 01:54 AM

Even the first lock shouldn't be that long. I have used my GPS in Israel after coming from the US, and then back in the US, and got a lock almost right away, within 1 min, even though it's locking to completely different sats in a totally different part of the world.

*hyedipin* · 05-26-04, 02:16 PM

I just (20 mins ago) received my Haicom MMF Bundle from BuyGPSnow. I first plugged the mmf to my Ax and ran the Mapopolis which said waiting for a fix.. then i closed that and run the Haicom's own fixing s/w. Now it has been running ever since, I still haven't gotten anything, indoors next to the window..

just now, I decided to down to my car, set up the Ax and leave it in my car.. It is in the car right now with steady red light.. I am waiting for it to get fixed position. I even opened the sunroof to support it..

I will get back there within 15 minutes to check on it and make sure i got battery.. I wonder how long it normally takes, and what tips do you have? Using CF.

A small questions, the charger I got with my Mapopolis Bundle, is it for Axim? Because i don't see any plugs for it go into the MMF..

Thanks~!

ecsw · 05-26-04, 02:24 PM

15 mins? Wow, it's a very cloudy day today here and I got fix within 1 minute after I turn it on this morning.

*hyedipin* · 05-26-04, 02:35 PM

It is the very first time..

Ok , I am back now, and all is in good hands! Thank god for not making me regret this purchase (for now at least), and hope not in the future..

WHen I was back in the car it was flashing (fixed) and i told my co-workers "i'll be right back" and did a very brief driving, and the minute I moved forward it started plotting! I did a small routing, it worked perfect and 300 feet to destination. Even said "Walk to destination" because our street was actually a park..

So far so good.

£dit:

I am indoors now, and there is no signal.. What are the limitations of this GPS ? A tunnel will be a sudden loss of position? A subway ? A tall building? A bus stop?

£dit (2):

Oh, and it is very foggy & cloudy in New York today.. (check the weather.com if you don't believe me)

tgreenstein · 05-26-04, 05:57 PM

Quote:

Originally posted by hyedipin

I am indoors now, and there is no signal.. What are the limitations of this GPS ? A tunnel will be a sudden loss of position? A subway ? A tall building? A bus stop?

Unlike, say, FM broadcasts, GPS reception is basically line-of-sight. If there is an object blocking the receiver's "view" of a satellite, you won't be able to use that satellite's signal. If enough of the available satellites are blocked, you won't be able to get a fix.

Yes, a tunnel will shut down the signal -- until you come out at the other end. A tall building will only affect the satellites that are "behind" the building from the receiver's perspective (meaning, reception in urban canyons can be seriously degraded).

Some routing software tries to get around the temporary loss of satellite reception in tunnels and urban canyons by projecting the location of the receiver by assuming that direction and speed have remained unchanged since the loss of signal. This can make it "look" like you're still getting a signal inside a tunnel even though you are not.

GPS receivers typically won't work in a building unless you're near a window (although, if you need a GPS to get around in a building you have some serious problems!!).

*hyedipin* · 05-27-04, 09:34 AM

Thanks Ted.. good literature!

To add to your last sentence, time to time I need guidance finding my way to my manager's office..if you know what I mean.. Especially before staff meetings..

Anyway

Do you think they would improve the way GPS works in couple of years and have it go through walls or like you said, turn them into something similar to radio waves?

One last issue:

I am using mapoplis, and when driving on one road, it showed me -number of times- on the road next to it. It always "pulls" to the right. If I don't choose "Stay on the Road" it will always show me to the right of the road (not on it, but right of it) and when I chose Stay on the Road (other s/w may use something similar) and if there is another road very next to it (service road of highway) it would show me on that service roads, sometimes taking the exit, although I did not.. What would you think of that? Is it the direction i am holding the Axim? Should It always be towards the front of the car exactly?

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