Thread: Iguidance 100 feet off w/ BU-353?

don't have this problem with my POS USB mouse, nor did I have it with my gr231 bluetooth, it sounds like a problem with the receiver, not the software

Okay, I had my brother drive my car while I play with the GPS. What I'm testing:

iGuidance 2.1.3 on GM-210 (SiRF II) on my carpc
iGuidance 2.1.3 on BU-353 (SiRF III) on my laptop
Garmin iQue 3600 (I think the map data is maybe 5 years old, definitely not SiRF III).

Preconceived notions before this test:
I always thought the GM-210 was great and that it never let me down. I've had it route me to wrong places, but it was the address that was bad, and not my position based on GPS. My brother's iQue never let him down either and we regard it as fairly accurate.

Testing:
The iGuidance used the same map data, with only the GPS receiver different. The iQue was brought along for fun. We tested while in motion (local and highway roads), checking differences in reported altitude, speed, and position. All the antennas were placed near each other (check the pictures). We also tested sitting in an intersection. The road is old and established, so shouldn't have changed with map data.

Pictures:
Sitting right at the intersection:


Antenna array:


iGuidance w/ BU-353 (note how far we're from the intersection):


iGuidance w/ GM-210 (also note how far):


iQue:



Conclusion:
In some intersections the reported positions were exact, in other intersections the reported positions were off by up to 100 feet. However, all positions were the same in all three devices. The only thing I can conclude is that the GPS receivers are precise, but the maps are inaccurate.

I guess I have mentally adapted to the inaccuracies that I didn't notice until I swapped GPS receivers and actually looked at the map. Same with my brother and his iQue - after using it all these years, he's adapted his driving to the map (when it says to turn in 100 feet, he knows it as basically 'turn right now' and ascribes the difference to when the map actually hits the point and when the sound clip says it)

Basically, nothing wrong with the BU-353.

i wonder if iguidance 3.0 is any better?? or anymore accurate.

Fantastic! Great report! Thanks.

Let me go mess with my bluetooth GPS receiver, i believe it's more accurate than that..

This comparison i did between a bluetooth GPS receiver and the BU-353. The bluetooth is running on the carPC and the BU is on a laptop; both running iGudance 3.0 (not UMPC). Here goes:

Couple more. I guidance mode, the difference between the two is about 10ft. as you can see in the picture. I received voice guidance a fraction of a second apart. Last, i stoped at another intersection just to make sure they both still reflected the same position.

I would also conclude it's the software that's giving that large error. Maybe the OS or PC itself is the colprit..

BTW, while moving, i always passed the intersection before the GPS..but not by much.

Hmm. I don't seem to have any problem with MM and a BU-353.

Maybe it's time for you to change software?

Well, not necessarily software, but just the map source data. Everything we've tested so far is based on Navtech data. Tree, a difference of 10 feet is within tolerance of GPS, so the precision is close enough I think.

Originally Posted by psyrex

Well, not necessarily software, but just the map source data. Everything we've tested so far is based on Navtech data. Tree, a difference of 10 feet is within tolerance of GPS, so the precision is close enough I think.

I agree, 10 feet is more than acceptable. Thanks for sharing your results.