Vehicles w/Windshields that May Cause GPS Reception Issues

[Emrol Ed]

I have had fairly good reception in a 2001 Chevy Silverado with my Earthmate USB receiver, yet my son has the same model, and he needs to put the unit on the roof to get good reception.

I recently bought a GlobalSat BU-353 (with the SiRF III chipset.) It is sensitive enough to pick up several satellites while indoors.

I did a comparison this morning to see how both units performed on the dash and on the Chevy's roof. I tried to take the samples quickly so that the satellite positions would not have changed very much.

(Edit July 1, 2007 - Rather than this being an Earthmate vs. USGlobalsat comparison, it really shows the difference between the Earthmate's SiRF Star IIe's chipset and the USGlobalsat's SiRF Star III chipset, and the effect of signal attenuation on both)


http://www.usglobalsat.com/item.asp?itemid=60

[Dennis Olsen]

DeLorme just came out with an Otter Box with magnet that the BlueLogger fits into. If you look on the right of the picture (where the arrows on the BL are) it looks like it has a wire/grommet hole for a cable, so the LT20 might work in it.

Where is the picture and ordering information? I checked out the accessories screens and couldn't find it.

[Dan Lawyer]

Sorry, I forgot to post the link to the Otter Box.

[roblopes]

[quote="Dan Lawyer"][quote="waldo"] My solution was to tape the receiver to the roof of the car and letting the door close on the cable--end of troubles. The bad part of this was that one has to remove the unit when one stops for the night and the taping has to be watertight if you are apt to be driving in rain. [/quote]
DeLorme just came out with an Otter Box with magnet that the BlueLogger fits into. If you look on the right of the picture (where the arrows on the BL are) it looks like it has a wire/grommet hole for a cable, so the LT20 might work in it. The LT20 is about the same width and height, but a bit shorter, compared to the BL so I know it will fit. I'd ask first before I got one though, I'm kind of surprised they didn't advertise it for either if it would work that way.[/quote]

I'm baffled by all this! I thought I had to go out and purchase something new to make my trips better only to remember I drove 3800 miles round trip with many stops and never had a problem with what I purchased from DeLorme. Magnetic this, magnetic that...... I don't need 12 sat's, I only need 3 sat's to get me where I need to be..... Right? I have more problems in my "wood framed and composite roofing garage" to pick up a good (usually drifting elevation) signal. Maybe its the metal nails used to fasten the composite roofing down?

2004 Ford F-150 with a custom built laptop stand with a FM transmitter transmitting DVD audio to the radio.

On average, I'm sure I had more than 6 sats providing information (I didn't get lost and that's why I purchased the software/hardware, NOT TO GET LOST!).

The only problems I had on this trip was passing the destination address that was actually at a higher elevation and completed roads stating "off track".

This thread seriously sounds like "Sales Chatter to me"!

I should purchase the OtterBox because (it says) the device can go 100 feet under water! Or was/is that a sales pitch? I really think they meant the encloser is certified to go that deep. I like my truck but I don't think we can go below the surface that deep with out some other "options" I'm sure.

If this is a true end user forum, it should be posted. I'll bet it doesn't!

[roblopes]

[quote="MBerndt"]We have an '02 Rendezvous which has the metal windshield. Wreaked havoc with the Illinois Tollway pass, too. I solved the GPS problem by sticking the receiver up in the sunroof, which is not "metalized".[/quote]

Your DeLorme GPS works with the Illinois tollway too?

[roblopes]

[quote="Dan Lawyer"]Thought I would post this site that contains [url=http://ezpass.com/static/info/exteriortags.shtml] [u]vehicles that contain metal in their windshield[/u][/url]. I haven't actually looked for a list of them, but noticed this in another forum. This is known to cause problems with GPS reception. Their list only goes up to 2003, so if I find a newer one I'll updated it. If anyone else does, feel free to respond to this topic with a link.

If anyone has one of these vehicles, or has this problem, you may solve it if you can get the GPS at an angle out a side window, which may not have this issue.

With the tags, they must be read and as they are fixed on the windshield, the metal probably has a much greater effect that it would with a GPS. You can move it around and it can read thru the "holes" in the glass where their isn't anything blocking it. I used to drive a lot of rentals in the late 90's and found some that I really had to play with moving the GPS (serial EM) around, but almost always found a place it would enough to get a fix.[/quote]

So I purchase a product that is marketed to work that doesn't and put it outside my vehical in certain conditions and hope it does only to rember to bring the device back inside when the conditions would cause the device to fail?

The DeLorme GPS and Maps package I purchased work as advertised.

[roblopes]

[quote="Dennis Olsen"][quote]DeLorme just came out with an Otter Box with magnet that the BlueLogger fits into. If you look on the right of the picture (where the arrows on the BL are) it looks like it has a wire/grommet hole for a cable, so the LT20 might work in it. [/quote]

Where is the picture and ordering information? I checked out the accessories screens and couldn't find it.[/quote]

The question is "why would you need it?". Doesn't what you purchased from DeLorme work?

[roblopes]

[quote="nabsltd"][quote="Dan Lawyer"]Thought I would post this site that contains [url=http://ezpass.com/static/info/exteriortags.shtml] [u]vehicles that contain metal in their windshield[/u][/url]. I haven't actually looked for a list of them, but noticed this in another forum. This is known to cause problems with GPS reception.[/quote]Although I have a 2001 F-150, I have the newer metal-using F-150 windshield (replaced due to road rock), a 2001 E250 van, and a 2002 Chrysler PT Cruiser...all three are on the list.

I never had an issue with my Holux GM-210 with any of my cars, and the newer Holux GM-236 even works underground, so a little metal won't stop it.

The DeLorme BlueLogger should do at least as well as the GM-210, and anything else "new" would have similar performance.[/quote]

When did the Holux GM-210 come out and what are the model cars have you had?

Underground? How far in the Earth have you gone and the Holux GM-210 still provide you accurate GPS information?

[Sanaghan]

"newer" doesn't mean "better." Reception depends on many factors.

1. Antenna design. You'd think it would be down by now to the best design, but it's not. Cell phones are a great example. The frequencies haven't changed, but I went on-line to find the best reception phone I could find during my last purchase. I pull one or two in with my 4 year old phone where others get "no signal." Many newer phones are worse. When a phone (or GPS) is designed, a new antenna that fits the case may not be as good as an older antenna that was better designed. And in antennas, bigger is always better.

(And or course orientation--the best antennas are directional and if your GPS isn't held in the right position, they don't work as well)

2. Circuitry. Is it just an antenna? Or is it an antenna with a filter? Or even better, a filter and amplifier. Or best, a big antenna with Digital Signal Processing and a low-noise amplifier? The smaller your unit, the lower the odds that any of that is in there.

[Emrol Ed]

"newer" doesn't mean "better."

Newer can be better, in some cases; the SiRF III GPS chipset being an example. I have acquired satellites indoors, where two other GPS receivers indicate no signals.

Sanaghan's comment on orientation gave me the idea to do further indoor tests with the BU-353. I placed it in three orientations: normal orientation, 90 degrees from vertical, upside down on a bed, and upside down on metal (an ATX power supply case).









Working under these conditions seems to indicate that it should work well outdoors under some degree of foliage and in "urban canyons". (I cannot test those conditions where I live)

[Dan Lawyer]

This thread seriously sounds like "Sales Chatter to me"!

I should purchase the OtterBox because (it says) the device can go 100 feet under water! Or was/is that a sales pitch? I really think they meant the encloser is certified to go that deep. I like my truck but I don't think we can go below the surface that deep with out some other "options" I'm sure.

If this is a true end user forum, it should be posted. I'll bet it doesn't!

This is a "true end user forum" and it's a place for customers to ask for help. This specific forum is for Tips & Tricks about using the products and getting around problems. Sometimes solutions call for buying stuff, and you yourself bought the program and a GPS to get around the problems of using paper maps or for some other reason, so you fell for the "sales chatter" if that's what you want to call it.

This specific forum is, according to the Forums Moderator Dan Brume, is to

Post any tips and tricks for any DeLorme products. Do not post requests for help in this forums

neither of which you are doing.

I posted about the Otter Box in this topic because it is one solution to the windshield problem, is to put it on the roof of the vehicle. Folks have been doing it for years. Some GPS come with magnets in the bottom, DeLorme's don't. Heck, I made up a small Tupperware container with a magnet, rubber grommet in a hole in the box for a friend many years ago, who had a Class C RV with a cab over, with the old EM Tripmate. He used it for years on the hood out beyond the overhang, called it his hoodscoop.

Just because your GPS works in your truck without any problems, doesn't mean it works in the thousands of other vehicles available. I started the thread because there are know issues with GPS signals getting thru some vehicles windshields. The Blue Logger is used by hikers, in boats, in private planes, and in vehicles that it can't get a signal thru the windshield. in all these cases protecting the BL from the elements is an issue. DeLorme sells a case for the BL, one with a magnet one without, to protect it.

The fact that it's advertised to go 100' under water, is telling a normal person that the case must be pretty well sealed and strong. You can duct tape the BL to your roof if you want, it will be waterproof as long as the tape holds out, that's your choice. Personally, I'll buy the Otter Box to safeguard my BL investment.

[Sanaghan]

"newer" doesn't mean "better."

Newer can be better, in some cases; the SiRF III GPS chipset being an example. I have acquired satellites indoors, where two other GPS receivers indicate no signals.

Newer *usually* means "engineering better" unless other pressures like cost and other features come in. I have a friend with the PDA/Cell phone--they spent a lot of money on that. For the price, I would have thought they'd put more work into the antenna design. Instead, it's the stubby antenna.

A lot of people love the nokia's, with no external antenna. Fashion was more important that what Nokia knew they could make better.

In the SirF III chipset example, engineering triumped--people wanted a better lock (at a reasonible price and size--no one wants to lug a lunch box sized antenna)

The (short) Sirf III home page says it grabs weak signals.
http://www.sirf.com/products-ss3.html
Their tech page says it better--just like I said it, actually. Instead of just grabbing the signal, the run it through a filter and a Low Noise Amplifier. They mention their GPS Core and "Correlation power"--that's another way of saying they do a bunch of signal processing to better get info from weak signals.

I believe it handles reflected signals differently as well, so in short the higher processing power with different software allows it to have 20 dB higher sensitivity. (Every 3db is double or half in power).

[nabsltd]

Underground? How far in the Earth have you gone and the Holux GM-210 still provide you accurate GPS information?

No place. Read again and you'll see that it is the Holux GM-236 that works underground. It is the same as the BU-353 that Emrol Ed mentioned above (they are basically OEM versions of the same receiver).

I can get accurate fixes using the GM-236 in my basement or in underground parking garages that don't have too much metal in the concrete. About 20' or so seems to be the limit, but that's still great performance.

[nabsltd]

They mention their GPS Core and "Correlation power"--that's another way of saying they do a bunch of signal processing to better get info from weak signals.

Yeah, the difference is orders of magnitude.

Typical GPS units have several hundred to several thousand correlators (basically, these are hardware linear equation solving devices). The Sirf III chipset uses several hundred thousand correlators.

[rockytop]

I do not have a problem with a metal windshield, but mine is with the windshield in our motorcoach. It is near vertical and I have trouble picking up a number of satellites great enought to maintain a good track. I sometimes have a yellow or red light for 40 - 60 miles or more. This seems to be a greater problem going south than it does any other direction. My idea is to cut the wire on the receiver, mount it on the roof under a glass dish or bowl and run the wire through a hole in the roof. I will silicone the receiver and the bowl to the roof. I have both an old receiver and an LT-20, but would like to put the LT on the roof. My question is, is it possible to successfully splice the wire back together without too much signal loss? I do not know if this is a single wire such as a coax or multiple wires or if you can buy special connectors for this wire, say at Radio Shack. Any thoughts or ideas will help.