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GlobalSat BU-353 S4 USB GPS receiver
Ken in Regina
I'm not sure I understand, Terry. Are you questioning SpadesFlush's statement that he observed less lag between the Viliv internal GPS and the S4?

Or just not sure whether my guesses about the possible causes of the difference he's seeing hold water?

...ken...
tcassidy
I find it hard to believe that a better GPS reduces lag. I have always suspected lag (which I have never experienced as I so rarely use S&T) is a function of the computer or the software being too busy doing other things to bother updating the position. Any GPS chipset operates at a bit rate allowing it to calculate position more than once a second...it is only that it provides the update once a second. So it is likely to produce something (as evidenced by SF's sawtooth track and one that Marvin produced years ago).

I also don't believe that S&T is smart enough to reject faulty locations based on HDOP (again as evidenced by SF's sawtooth).

Of course, these are only the opinions of a person who never uses S&T except for trip planning!!

Terry
Marvin Hlavac
Quote:
Marvin, you have both and access to a large metropolitan area. How about a hands on!!
Terry, I'm planning to venture to downtown Toronto for a side-by-site S4 vs S3 comparison this Saturday. Then I will edit my earlier post above by inserting there the test results.
SpadesFlush
@ Ken. Until I used the 353S4, I was reasonably happy with the GPS reception on the Viliv. I do not think it has anything to do per se with whether the antenna chip is built in or not except that one might have a bit more positioning flexibility with a 1.5m cable. For instance, I placed the S4 way up front where the glass meets the dash, whereas I usually would have the Viliv about 2 inches from the steering wheel.

@ Terry. I too thought the Viliv has the Sirfstar III chip, but I did not want to make that assertion without researching it. So long as it is reasonably well isolated from the other internal electrics (as it seems to be) I cannot see why it would function better on a tether.

@ Terry. As I tried to convey in my post, it was my impression only that there was a shorter positioning lag. I think there could be a logical explanation for that along Ken's lines. I am happy to stimulate the controversy so that perhaps the Forum can develop a concensus view on the subject based on a broader experience base.
t1d
Wow, you guys are just great! What great information! What excellent research... chipset verification, road work, live comparisons, etc... Thanks!
Marvin Hlavac
I just posted test results of NEW VERSION vs OLD VERSION. I edited my post above (post #4) by adding a screen shot and some comments.
SpadesFlush
Thanks for the test Marvin that more or less conforms to my experience. I would expect for most non-urban users (probably most users) that these improvements alone would not be a sufficient basis for up-grading from the S3 to the S4. However, other considerations might do the trick, such as shortened start-up times or, if in fact it is there, reduced navigating lags.
tcassidy
I tried to see if I could experience lag running S&T 2011 on my Fujitsu Slate. It has about the CPU power of a netbook and I loaded it with GPS Gate, GPS View, 2 instances of S&T 2011 and a screen capture program. I had to use an unpowered USB hub to connect the S3 and S4 as the slate only has one USB port. I assigned the S3 to GPS Gate and used its ports for GPS View and one instance of S&T; the S4 was connected to the other instance. The computer was certainly taxed but seemed equal to the task.

I took a 40 minute trip with the screen capture program set to 20 seconds. Unfortunately, I was unable to determine anything about lag or the differences of the GPS. From the screenshots, occasionally one was leading slightly and at other times the other but the differences were miniscule. Sometimes the S4 showed more satellites and sometimes the S3.

The difficulty is there are no problem areas for GPS around here except the park this side of Victoria. I didn't want to drive that far just for a test so the worst I saw was 5 satellites and usually 8 or more.

As I pushed the computer hard enough that Win 7 eventually complained, I can no longer suspect lag to be due to this. However, until I can see it, I'll stay out of the discussion!

Terry
SpadesFlush
The issue of 'lag' is difficult to deal with; it is hard to quantify. I certainly will need a lot more experience under my belt to draw any firm conclusions but I don't think I will be making any A-B comparisons. I will just be using the S4.
melbaron1110
I own a 45ft Columbia sailboat that is docked on Lake Pontchartrain in Louisiana. On board I have a Hp 19'' laptop with Diginav GPS navigation software that is linked to my Autohelm Autopilot. The computer controls my Autopilot. I bought a Globalsat SIRF III USB receiver 2 years ago. The unit worked great in open water but did not do well in close quarters. The channel that leads back to my home port is about 2 miles long and about 60 ft across. The Sirf III would let you wander 30-40 ft on port or starboard side,which would put you into the marsh on either side. I sail a lot in the evening as it is much cooler than the daytime summer heat in Louisiana. Once I got to my channel markers leading into my home port channel I would have to rely on spotlights to light up the channel as I could not use the laptop. Last month I purchased the new Globalsat Sirf IV (s4) and installed it into my laptop. My best friend (Nick) also has the same setup on his 28ft Morgan sailboat. We decided to run the both laptops on board my sailboat, and do a comparison between the two Globalsat receivers.The difference was astounding. Within 10 minutes we realized the S4 was far superior to the old model (sirf III). I had the Autopilot taking commands from the laptop with the new S4, and it kept my boat well within the channel. The boat would wander around 8-10 ft from port to starboard side and then the computer would correct it. Both Nick and I were very impressed with the new S4. Nick has just ordered one for his laptop. What I like about Globalsat is that it is portable and I can just take it with me when I leave my boat. Other marine GPS antennas you must permanently attach to your boat, so the portability is a real plus. Just a note... Even though I rely heavily on my Autopilot for steering I am always close at hand incase of a breakdown on the Autopilot. Your Autopilot does not avoid obstacles in the water, so you always need to keep a sharp eye out for problems... Great job Globalsat!!!
SpadesFlush
Welcome to the forum melbaron and glad to hear of your positive experiences with the S4. Although most posters here are more concerned with terra firma applications, your results should be viewed as further justification for going with the S4 over the S3 although the differences seem to some to be inconsequential.
melbaron1110
Hi Spadesflush. I totally agree with you when it comes to applications. The simple truth is most people will be landlubbers who use it. It does not have to be as accurate on land as they have painted lines to follow, but on water it can make the difference in being on the rocks or avoiding them. I like this forum and will be in contact again.
Ramja
Quote:
Originally Posted by SpadesFlush
Ken, these are similar preliminary observations to what I am seeing.

I note that you got the GPSinfo program working. I have not. Even though the GPS is registering in Streets and Trips, GPSinfo does not detect the BU-353S4 when I try to conduct a scan. Any idea what I am doing wrong?
Check the drivers. May need to update. I am using the S4 on the road and it works with Streets and Trips, Co-Pilot V8 and Deloreme.
ben2go
Hey guys. After a long break, I am back. My new project is building a carputer from a Raspberry PI model B. I am running Rasbian Linux distro for my OS.Do you guys have a resource for Linux drivers for the Global Sat BU-353? I feel that if I could get the proper drivers I could probably find a program to handle mapping duties. I am open to suggestions on that too. I'm hoping to have a complete computer and media center in my car for traveling. To bad it's not a black Trans Am.
Ken in Regina
Just a thought.... you could download the Linux BU-353 driver from the Globalsat web site.

http://www.globalsat.com.tw/download.php?menu=3

Just select the appropriate items in the three dropdown lists and you should be good to go.

...ken...
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