Need a BUNCH of help!

fareast1 · Occasional Visitor Joined: Nov 10, 2003 Posts: 2

Sorry about the forthcoming questions, but I am really struggling here.

I have an Ipaq 5555. I am trying to buy a GPS CF add on for it but my intent seems to be out of sync with most manufacturers products.

First I live in Japan. I cant seem to find any English maps here even though this place is recognized as one of the most prolific GPS navigation locations in the world. (With good reason) Any ideas?

Second and possibly more importantly, I race motorcycles and want to use the system for several things.
I want to time laps, and data log for mapping purposes. I do not believe that 1hz refresh rate will be sufficient for this. Obviously accuracy is important for this. From what I can see this level of accuracy is only available on VERY high end models with dual receivers. Any thoughts?

For those who do not race, I want to be able to identify segments of the track that I was faster or slower on, corner entry speeds, exit speeds, track location at turn in, etc.

Even if the software is not available, if the hardware is capable of this level of accuracy, I can have the software developed.

While we are at it, could anyone tell me if WAAS is compatible with the Japanese system? (same frequencies etc.)

Also, if the error is consistently the same. IE if the accuracy is within 5 meters will I be at the exact same point each time I get the same coordinates. I don’t care if I am 4.3 meters off the true location as long as each time I am there I am the same amount off. Will the error change with the various weather conditions?

I appreciate any help you can provide.

FarEast1

lbendlin · Posted: Tue Nov 11, 2003 4:28 pm Post subject:

Hi Fareast,

welcome to the forum....

Bad news first - none of the publicly available GPS receivers have a refresh rate below 1 second. Even if you would use dual receiver technology you would still end up with the 1 Hz rate coming from the satellites. In-car navigation systems compensate GPS blackouts by coupling with the car's inertial system for measuring speeds - maybe you can do the same on your bike to fill the gap between the seconds ? You just need to make sure that your bike's clock is in sync with the GPS clock.

Why are you fixing on a CF GPS? Wouldn't a BlueTooth GPS receiver work better for you?

As for map material - are you referring to street navigation software or to topographical software? I'd guess your racing track is not part of the public street system?

The WAAS/EGNOS enhancements will only give you better location accuracy, but they will not increase the sample rate.

Is the error consistently the same? Of course not, that's why it is called an error! There are tons of influencing conditions, from signal reflections to snow clouds to solar storms to earth models. No matter how hard you try, your GPS position will wander around within the range specified by the DOP. That's just how it is.

GPS can help you with some of the surrounding data for your race timekeeping, but you should not try to use it as the system of record. It simply wasn't designed for that.
_________________
Lutz

Report Map Errors here:
TomTom/TeleAtlas NAVTEQ

fareast1 · Occasional Visitor Joined: Nov 10, 2003 Posts: 2

Hey Lutz,

Thanks for the reply.

I suspected those were the answers but needed to sanity check them anyway.

The maps I was referring to were navigation maps –street level. I am sure I could generate my own or edit existing ones, unfortunately they would have to be retouched with each new update.

I expected to go with an amalgamation of BT / CF/ and mouse.

On the refresh rate, do you know why the standard is 1 HZ? Could you explain a little to me? I am thinking that the signals are there and bus speeds are probably around 100 HZ. If I could data log the information, I could process it later on a ground station. This would limit the resolution to the logging speed. (Assuming I could somehow pluck the unprocessed data from the sensing device). I was thinking the BT would limit refresh rates.

I have seen tests done with DGPS that are amazing for clarity and error reduction. This is what got me looking at the WAAS (MSAS). The data looked usable but again at 1HZ there just aren’t enough data points for reasonable analysis.

I can see the technology is there, but not available to the average consumer and I can’t afford the high-end systems. With the IPAQ, I have memory and processor speed to burn. Since the racetrack is pretty small, couldn’t I use some kind of kinetic mapping?

Again, thanks for the input. I am open to any further comments or thoughts.

FarEast1

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