For the second time, when we left Jomtien for the drive home my 3750 would not pick up a signal for at least the first 15 minutes or more. This must be a defect (right?) because nobody would tolerate a GPS device so imperfect. Or is a poor/non-existent GPS signal common near Pattaya these days?

I am assuming catching/holding a signal is mostly a hardware issue ... or is it?

Edited January 17, 201313 yr by Lopburi99

Not being funny, but did you try turning it off and on again. Might work.

Had similar experience to you with my Garmin. Sometimes seems to take forever to get a signal. Annoying.

I thought the same and tried that multiple times. No change. Tried repositioning my dash holder. Still didn't make a difference. It just magically came on somewhere up highway 7 finally. By then I was ready to throw it out the window, because the day before the Bangkok street map (ESRI) was way off causing us untold grief. I don't know how many times I saw the bloody Rama IX off ramp sign.

Edited January 17, 201313 yr by Lopburi99

I've got the 3760 (same as the 3750 but with Oz map as standard) which i've used all over Thailand, Laos, Singapore, the Middle East and Oz.

I've not had a problem picking up a signal apart from 2 areas. For some unknown reason it takes forever to pick up a signal around Suwanaphum and in the middle of Sydney.

If you had not used the unit for awhile (say 1 week) it may take longer to re-aquire the satellites. Not really sure if this is true with modern units but it sure was with the earlier models. The ephemeris data which describes the orbit of the satellite used to be valid for 7 days before a new one was required. Without accurate ephemeris data the receiver will take a while to aquire a position solution.

If you had not used the unit for awhile (say 1 week) it may take longer to re-aquire the satellites. Not really sure if this is true with modern units but it sure was with the earlier models. The ephemeris data which describes the orbit of the satellite used to be valid for 7 days before a new one was required. Without accurate ephemeris data the receiver will take a while to aquire a position solution.

Interesting... We had a signal all the way from Lopburi to Jomtien the day before. Do you know if it searches for different ephemeris data upon power up from different distant locations? Is more than one satellite involved?

Edited January 17, 201313 yr by Lopburi99

If you had not used the unit for awhile (say 1 week) it may take longer to re-aquire the satellites. Not really sure if this is true with modern units but it sure was with the earlier models. The ephemeris data which describes the orbit of the satellite used to be valid for 7 days before a new one was required. Without accurate ephemeris data the receiver will take a while to aquire a position solution.

Interesting... We had a signal all the way from Lopburi to Jomtien the day before. Do you know if it searches for different ephemeris data upon power up from different distant locations? Is more than one satellite involved?

Maybe this helps:

http://www.noeman.org/gsm/garmin-tutorials/141508-reading-nuvis-satellites-map-page.html

It shouldn't have a problem re-acquiring satellites except when you transport the unit many hundreds of miles or more from its last location - like get on an airplane, drive long distances with it off the entire way, etc.

Going from like Bangkok to Chiangmai without it, then starting it up once in Chiangmai, it would have only a short delay in re-acquiring satellites.

My older Garmin doesn't work on the dash of my father-in-laws Isuzu SUV. I think it has to do with the reflective coating on his windshield. I hold the GPS unit out the side window, works fine. Put it back on the dash, loses its satellite signals. Me thinks an external antenna would solve that problem.

If you had not used the unit for awhile (say 1 week) it may take longer to re-aquire the satellites. Not really sure if this is true with modern units but it sure was with the earlier models. The ephemeris data which describes the orbit of the satellite used to be valid for 7 days before a new one was required. Without accurate ephemeris data the receiver will take a while to aquire a position solution.

Interesting... We had a signal all the way from Lopburi to Jomtien the day before. Do you know if it searches for different ephemeris data upon power up from different distant locations? Is more than one satellite involved?

I really do not know for sure. I used to work with some of the very first GPS positioning systems in the early 80's, these were 19" rack mounted (full rack) which included a caesium atomic clock. At that time the ephemeris data could come from any of the satellites. As there were only about 8 birds in the sky back then, there were occasions when you had no satellites visible. We had a log of the latest ephemeris data which we kept; this consisted of 20 x 20 digit numbers which had to be manually input to reaquire the satellites when they became visible again. I remember that the GPS antenna alone cost over USD 100K and I suspect the whole system would have cost more than a million. We used to joke that one day all of this would be built into a watch ala Dick Tracy. Amazing how quickly things have advanced in the last few decades!

Edited January 17, 201313 yr by canman

One would expect any GPS receiver to take time to initialize occasionally I recall based on download time to get an updated almanac message broadcast from any GPS satellite? It can take up to 12.5 minutes for a GPS receiver to download the complete almanac from a GPS satellite as the download baud rate is slow. And that is if you get the message from start, so up to 25 minutes in an extreme case where one just missed the start and effectively waste time for it to end and restart. A poweron/off helps to get another to start quicker sometimes helps. This almanac is only usually needed when the existing receiver unit almanac is out of date or the unit has moved several hundred km in position. Otherwise a much faster warm boot is possible using saved data.

Nowadays receivers coming in phones with Assisted GPS or GLONASS probably have other tricks in them as well to speed things up?

Never even heard of a receiver unit almanac. Is it used by a basic GPS device like mine? Do I need to wait for it to download too?

Edited January 19, 201313 yr by Lopburi99

I have an ancient Garmin eMap and it has always been a pain to acquire an initial fix.

Even an hour or so after arriving and preparing for the next journey.

Not so with TomTom though.

Never even heard of a receiver unit almanac. Is it used by a basic GPS device like mine? Do I need to wait for it to download too?

Every GPS receiver needs one. Here's a brief summary. http://en.wikipedia.org/wiki/Time_to_first_fix

With the advent of mobiles, wifi enabled systems assisted GPS had sped things up a lot. The bog standard stand alone GPS (like my old Garmin 48 hand held from the 90's) relied on the slow baud rate of the GPS satellites message to get the almanac for a cold start.