I have Garmin Mobile PC software only with basemap and CNNT NA 2009 hooked to a Dell X200 PIII with 586MB RAM running WinXP Pro SP3 using a third party 2007 vintage USB GPS receiver (which works fine for S&T 2007, I have "cleaned" the original box - got it from pacificgeek.com so not sure the manufacturer or what exactly it uses, but I "know" it is working as when it is not hooked up GMPC does not find a GPS device, when it is hooked up it finds it on "serial port 3" - (receiver uses Arcon Micro USB to UART drivers) and then starts showing satellites pretty fast) and on the GPS Info screen I am showing 9 different satellites with full blue bars, yet GMPC is staying on Acquiring Satellites, will not give me a fix. At one point Sunday evening I had it give me a fix and was able to drive around and it seemed to be working fine, however, now - nothing, just stays on "Acquiring Satellites". This is when sitting still (sat for about ten minutes) or moving. GPS receiver is on top of my pickup, full clear view of most of the dome of the sky, laptop inside. Any ideas? Might I need to change the datum? What exactly ARE the different datum settings in GMPC for?

It sounds like a problem with the GPS. The display you are referring to can be really misleading if you make the wrong assumptions about it. When a satellite icon shows up on the circle, it just means that the GPS is reporting a satellite in that portion of the sky. The signal bars mean only that the GPS is reporting that it's seeing a good quality signal from that particular satellite. It does not mean it's able to make any sense out of the data. At least not yet.

It sounds like even though it's seeing a good number of satellites and the signal strengths are good, the actual data coming from the GPS has conflicts that are giving Mobile PC heartburn. Mobile PC will report "acquiring satellites" until there are at least three satellites the GPS is sending good data from.

If you are interested in understanding at least a little about how this stuff actually works, check this out.

Global Positioning System - Wikipedia, the free encyclopedia

You don't need to read the whole thing. Just scroll down to section 2, Basic Concept of GPS. Read the short part up to the Position Calculation Introduction. It gets a little heavy at that point. Then scroll a little further down and check out the neat animated diagram of a typical satellite constellation and read the little blurb describing it.

The map datum does not affect Mobile PC's ability to figure out a location from the satellite data. It affects the display.

Simplest is to leave it at the default (WGS84). That's what City Navigator is built on.

If you really want to understand map datum take a look here:

Map projection - Wikipedia, the free encyclopedia

Reader's Digest version: it has to do with the shape of the earth, or rather, our understanding of the shape of the earth at different times in history and our ability to mathematically define it for mapping purposes.

...ken...

Isn't the 'acquiring satellites' message forever what you get if you try to use a GMPC hardware version with a different GPS?

Terry

Don't know. Haven't got a hardware version. But it's also what the software-only version does when you try to use a Garmin receiver with it.

The difference is that he's had a successful lock once. And he hasn't reported any of the other messages you'll get in either of the above situations.

With the software-only version, it only shows "acquiring satellites" for a few seconds. Then it changes to "Invalid GPS". I'm guessing that's the same thing you would see from the hardware version with the wrong GPS receiver.

...ken...

Okay, you were not kidding with "and it gets a little heavy". Is it possible that my system is just not storing the almanac info (from the "heavy" text: "The first is to assist in the acquisition of satellites at power-up by allowing the receiver to generate a list of visible satellites based on stored position and time, while an ephemeris from each satellite is needed to compute position fixes using that satellite. In older hardware, lack of an almanac in a new receiver would cause long delays before providing a valid position, because the search for each satellite was a slow process. Advances in hardware have made the acquisition process much faster, so not having an almanac is no longer an issue.") and is having to find and read all that info each instance of start up - I'm not even certain the system CAN "store" the almanac info in the data streams, which if my receiver is old enough it might work fine with more rudimentary mapping systems and just is not "fast" enough to work with GMPC or I am not giving it enough time to read all the data? This might make sense in that the day it DID work, I ran back in my apartment to grab my wallet and the system was on for that length of time, where subsequently I sat in the car staring at it impatiently and when I began moving it became difficult for the receiver to transmit and GMPC to process the data. I am going to try one more time to just leave the vehicle in the open air for a good long bit tof time and see what happens, however, it looks like for practical purposes I need to begin looking for a new receiver unit. I'll dredge through the posts for hints on a good receiver to look for, but if anyone feels like chiming in with their suggestions on a good but lower priced USB based receiver, feel free! And thanks Ken for the points to the wikis, always love expanding my knowledge, wish those would have been around when "I" was going through college, so much easier than culling the libraries.

You are reading far too much into that information. If you are seeing 9 satellites, the GPS already has downloaded and stored the almanac. It does that from the first satellite it sees; that is how it finds the other ones.

The GPS data required to run a navigation program such as Mobile PC or S&T is miniscule. Speeds of 4800 bps are easily fast enough.

Check to make sure your GPS does still work with S&T. Also, make sure you have a recent version of Mobile PC. If all else fails, chuck that GPS and get a new one!

Terry

I have to disagree mildly with Terry.

Even new GPS receivers with the latest technology will take some time to get a location fix if they have not been used for a week or more or if they are a significant distance from where they were last turned on.

It's called a "cold startup". One of the first things we (including Terry)recommend to people with a new GPS and having trouble getting a location fix for the first time is that they take it outside, fill themselves a mug of their favorite beverage and prepare to wait a bit. Anywhere from 5 minutes to as much as 20 minutes or more. Even for the latest technology.

Once some of the better new receivers have gone through a cold startup you need to leave them off for quite a long time or move quite a long distance to force them back into a cold startup situation. The good ones, like my Garmin eTrex Legend HCx handheld, can sit for two or three weeks at a time and when you fire it back up it will take very little time to acquire a location fix. In the case of the eTrex "H" series, as little as three or four seconds sometimes.

On the other hand, older technology, like my Garmin iQue 3600 PDA, will take many minutes to reacquire a location fix after being off for only a couple of days. Even when it's turned off long enough to gas the car it can sometimes take 15 or 20 seconds to grab the location again, depending on atmospheric conditions and its view of the sky.

I agree with Terry that as a sanity check of the receiver you should also give it a try with Streets&Trips. If you don't have it already you can download it for free to try out. This isn't to get you to try Streest&Trips but to give you a free option to test the receiver.

Another free option to test it is to download GPSGate (14 day free trial). The system tray icon changes colour to reflect the state of the receiver. It will turn light green when it finds the receiver and the receiver reports that it's seeing satellites. It will turn dark green when the receiver reports a location fix.

You might as well make certain it's the receiver before springing for a new one.

...ken...

I would have said the internal battery was weak or dead except for the fact it is showing 9 satellites. Even my UMPC which usually has to do a cold start is up and running by the time it has 5.

Terry

Went out today and let the truck sit in open air for about 45 minutes with app running, still 'Acquiring Satellites'. So, installed EarthBridge and GPSDiag (found in other posts - thx!) and get no joy. Satellites are seen in both, but cannot obtain fix through either one (see attached images if I can get them to work...) So, it seems the receiver is on the fritz. My former boss has a receiver he got with Streets & Trips a few years ago (Pharos GPS-360) that he is going to give me, I am going to see what that says, plus I found a link to an inexpensive BT adapter for 20 bucks which I am going to try with a USB BT dongle I got for a couple bucks. I am trying to stay low cost here for now to see what happens.

Does any of the above diagnostic tools have a feature to reset the USB GPS receiver to "factory settings"? If yes, try it.

The Pharos 360 is definitely a good value at 'free'. However paying $20 plus shipping for a questionable 4+ year old Bluetooth sled (plus extra for a BT dongle if you don't have Bluetooth) is stretching reliability.

The 360 is already USB capable or you can go with a new complete Bluetooth GPS for about $40. In fact Semsons has one on sale I've never heard of for under $20.
Amod ABG 108 Bluetooth GPS Receiver (WAAS/EGNOS support) (Your Choice of Free Mount) - Bluetooth GPS

***Marvin, Why is this thread displaying wider than usual...very annoying.***

Terry

It's the way the images are posted. With two of them side by side it's forcing the scrolling. With one message that wide, it forces the entire thread to have to scroll horizontally.

That's why it is generally encouraged to "attach" the pictures to the message using the "Manage Attachments" button rather than embedding them with the {img}{/img} codes.

...ken...

I must apologize for my 'newbie'-ism with the screen shots, my life in forums has been entirely text based and I simply looked at the tools provided above the text editor. This will not happen again, I tried to get the images to place one on top of the other and it appears this did not happen. (Looks different in my instance on Firefox, the images appear to be stacked)

I tried the Pharos 360 USB device to no avail today, I installed the driver from Pharos' site, restarted, then plugged in the device and XP showed it as a USB-Serial Adapter and would not install, it would not use the PL-2303 driver and I could not figure out how to force it.

So, I await with baited breath my Amod ABG 108 BT receiver (that is the one I had found for a low, low price and includes a free window mount for the unit) from Semson's. It has circuitry built in to power the device off when bluetooth signal is lost, which was the deciding factor in choosing it. I will endeavour to relay my experience with it when I receive the unit. I am using a BT dongle I purchased from DealExtreme dot com for $2.46 with free shipping, it works MOST excellently and is by far the smallest dongle I have ever encountered (https://www.dealextreme.com/details.dx/sku.11866), I highly recommend it for BT (I, of course, have not used it with GPS yet, I will relate that experience later)

1. I added an empty line between the pictures, and now it looks OK. It looked fine in FireFox, but I checked it in IE, and that's where the problem was visible.

2. Amod ABG 108 BT is based on a chipset that can track GPS signals at -152 dBm. That is something that one could expect from GPS receivers 5 years ago, but it is not that great by today's standards. That explains the low price.

Well, I guess 'ya gets what ya pays for', but if it gets me from place to place, it will work (unlike the two I already have). I had been using a Garmin C330 (Dad is still using it in his van) and currently have a Garmin C510 that was a Euro model refurbed with North America but I just cannot interact with the 3.5" screen well enough, thus the exploration of GMPC on the 12" laptop screen. I tried to find reviews of the Amod and searched these forums but only found one site that spoke of the sensitivity issue and whatever it is, it will be equal to or greater than what I had, and my needs are basic compared to others. I have very little 'urban canyon' travelling, mostly out among the cornfields of Northern to Northwestern Ohio and through the middle of Michigan. Perhaps when I have it in my vehicle and try it out I will post a review of it.

And Martin, much appreciation for the edit, I rarely, if ever, use IE any longer, thus my ignorance of the issue. IE 8 'may' be safer than it was in previous versions, but I have Firefox tuned to my liking and it's a personal choice in the 'browser wars'.

The Amod unit should work fine as long as you position it in a place where it has good view of the sky in many directions.

Thanks Ken for pointing out the problem and Marvin for solving it. I will stick with IE - regardless of how wonderful Firefox is - as it gets the job done.

The BT dongle looks like a good deal. How does DX make any money selling it at that price with free shipping? Not much room for mark up there unless they get them for free.

Terry