NMEA/SiRF mode?

[Quantum]

Omzy, the WAAS/EGNOS box is represented by Holux as turning on that mode. Ostensibly, when you set WAAS/EGNOS then disconnect GPSView, it leaves it in that mode until the battery is lost, according to Holux. But I have no evidence that that is the case, as I have not seen any birds above 30 since I set it. (Here in the Colonies, 35 & 47 are the WAAS birds) If not in WAAS mode, you do not see those birds in GPSView under any circumstances.

I understand that when you restart GPSView, the box is unchecked. My theory is that GPSView is not advanced enough to query current mode. But sorely doubt that this method of turning on WAAS works. Everyone who's been successful with WAAS switched to SiRF to set and then back to NEMA, but this has not been reported with the 236.

I've only seen bad experiences setting the 236 to SiRF, and am afraid try it, as I am desperately dependent on my nav system, being in a new town. But something Mike says above, seems to imply that you can force SiRFDemo to stay in 36,400. If this is the case, it may allow its use with the 236. There are at least 3 other utilities, but no reports with the 236.

What Powersave does, is apparently unknown to science, as I have asked repeatedly. But if memory serves from way back, there is some big disadvantage to it.

[Omzy]

So what exactly does WAAS/EGNOS do, what advantages does it offer?

And how would I turn it off again using GPSViewer?

[Quantum]

[Quantum]

Sh!t, Mike has disappeared. So again, I get no answer to my SD questions.

[lbendlin]

- There is little to no chance to see a WAAS bird when you are above a certain latitude. In addition, WAAS seems to be interfering with the correlation method used by the SiRF III chipset. You may actually decrease accuracy by enablin WAAS. So, keep it off.

- Static Navigation is mostly bad. There are some situations like when you wait at a traffic light in an urban canyon where SN would help to keep your position indicator steady, but if you use the device below 4 km/h then SN is contraproductive. So, switch it off

- Power Save is technically "Trickle Power Mode" where the receiver acquires the position within, let's say, 200 ms, and then goes to sleep for 800 ms. Theoretically this will give you a fivefold battery life. In reality you will be lucky to get 50% more out of the battery. With today's receivers you look at standard run times of 9+ hours (the "Gold Standard" GlobalSat BT-338 gives you 15 hours) the importance of Power Save has reduced greatly. So, keep it off.

- The GPSinfo program doesn't show the current status of the receiver because in the SiRF protocol you need to explicitly query the status.

- The older TomTom GPS driver can only be used to switch between SiRF and NMEA. You cannot use it to set any other SiRF parameter.
_________________
Lutz

Report Map Errors here:
TomTom/TeleAtlas NAVTEQ

[Quantum]

Thanks Lutz. I only wish I knew a safe method to turn off SN for the Holux236. SiRFDemo certainly isn't that. I vitally depend on GPS, being new in this town and being out of warranty, so must be cautious.

I do not like shorting the coin cell. Very bad for it.

[mikealder]

Quantum, Please download and install MMSirfSetup.PPC2K ARM.ZIP from this location http://www.gps-assist.co.uk/forums/showthread.php?p=59#post59 you will need to rename the downloaded file so it simply reads MMSirfSetup.PPC2K ARM.CAB then simply copy it to the memory card and run the file on the Pocket PC by selecting it from within Explorer.

You can then use this application to turn the SN ON and OFF quite easily. It works fine on my 4700 running WM2003SE, but I have had trouble getting it to work on my WM2005 equipped devices - Mike

[Quantum]

Wow, here's an eye-opening article on the effectiveness of EGNOS in Paris.

The effectiveness of EGNOS was quite different between the two birds there, one making things worse, and one better.

But more startling is the accuracy of the Nemerix chipset, when compared with the dizzy wandering of SiRF3. I thought we had the best chipset, but nope.

[Quantum]

OK, I can now confidently report that Holux's util, GPSView, does not actually switch on WAAS/EGNOS, as we had suspected.

The good news is that I've found a utility that does, and which works with the Holux236 via bluetooth. I have an IPaq4700 running WM2003SE.

The util is SiRFTech. I should warn you though, that this utility is like playing with fire. If you are careless, you will be sorry.

You'll connect to Com8 at 38400. After using each tab in the util, you have to close it, which is a little weird. Once running, check the NEMA tab, and make sure you get live data. Then switch to SiRF mode, staying at 38400. This will take a couple of tries on the 236 (as it does with all other pods). Once NEMA seems dead, close it and open the SiRF tab.

You will notice that the data is now filled in in each SiRF tab, and that Static Navigation is off in the 236 from the factory, which is a Good Thing(TM). If you choose, turn on SBAS (WAAS/EGNOS). Again, do not fiddle with anything else, unless you would like to have a heart attack. Be sure to switch back to NEMA, if you want TomTom to actually work. This may take a couple of tries.

I will now drive around with this turned on and see if I get my WAAS birds. I doubt I'll notice accuracy difference in TomTom, but unless there's an obvious problem, I am leaving WAAS on. All the inaccuracy reports are on EGNOS, and this finds that in fact one EGNOS bird is worse but one is better. Since WAAS is used for munitions and aircraft landing in the US, my theory is that it should be an improvement over nothing.

It seems I have the older 3.1.0 firmware. I guess there's no way to upgrade this without their fscking cable which I'm not going to buy.

Thanks to those who've helped. If you hadn't I would not have brought this info back to y'all.

[Quantum]

Drove around Seattle today with WAAS enabled + running GPSView, and just about everywhere I went, I saw WAAS 35. (This is one of the two WAAS satellites for the US) Never saw 47 though. (The other one)

However, I only ever saw 35 as a red outline bar in GPSView, never as a blue bar as with the other 10 GPS satellites in the sky I usually get here.

Why would it give me only a red outline bar, even though it gives signal strengths over 40, which is as high as most other birds here? Needless to say, I never got a DGPS 3D lock.

At this stage, I have invented what seems to be a new thing to science; achieving WAAS on the Holux 236, and actually seeing one of the WAAS satellites, but unfortunately I have not yet locked its almanacs.

We are on the cutting edge here, peoples...

[Quantum]

Yes Greenglide, this is what I've said several times. Nevertheless, it is doubtful that WAAS is worse than a poke in the eye with a sharp stick.


I guess I am stuck, at this point. I only ever get the red-outlined bar in GPSView, which tells me WAAS is not being actually used. The bird is visible all over town, but something's wrong. I've left it sit for 8 hours, and no improvement.

I suspect it is one of the DGPS parameters, but I can not find a reference anywhere describing what these parameters are, nor advisable settings for them. These are not made generally available I guess, to keep the shoe salesmen form mucking up their GPS, but ironically those who are technically-proficient, cannot safely set the parameters, without knowledge.

The settings I'm thinking of in particular are:
- DGPSSource|InternalBeaconFreq (Is 0 some acceptable default, or does it -disable-?)
- DGPSSource|InternalBeaconBitRate (Should this be 10, or 50?)
- DGPSMode|DGPSSelection (presumably should be Auto)
- DGPSMode|DGPSTimeout (Is this when it stops looking for WAAS birds? 18 seconds is too short. And is this after Hot, or Cold restart?)
- SBAS|SBASPRN (Which of the WAAS birds provides ionospheric data, the largest cause of error?)
- SBAS|SBASMode (Seems that 'Testing' is most forgiving, as Integrity throws out non-verified WAAS data)
- SBAS|Timeout (Presumably should be Default)

I am also interested in:
- ModeControl|TrackSmoothing (unchecked)
- And the lowest elevation WAAS is allowed to work at, which I suspect is ElevationMask|NavigationMask (now 5, which is fine, if this is what I think it is)

I can't even find out WTF a 'DOP' is. I'd like to know about setting DOPMask|DOPSelection.

Now, a shoe salesman would go ahead and try these settings without study, but I sure am not.

If you think that I shouldn't know this, just because I don't, stow it, Buford.

[lbendlin]

DOP = dilution of precision. a measure for the statistical likelihood that your indicated position or altitude is not just a pile of dog poo.
_________________
Lutz

Report Map Errors here:
TomTom/TeleAtlas NAVTEQ

[Quantum]

OK, so say hypothetically you have a setting called, "DOP Selection", and its choices are in a pulldown:
- Do not use (default)
- Auto PDOP/HDOP
- PDOP
- HDOP
- GDOP

... which would you choose? And what effect would the choice have?

And if you had other parameters called,
"GDOP Value"
"PDOP Value"
"HDOP Value"

... (all default to 10), what would you think of that?

[lbendlin]

these settings give you the option to discard all readings above a certain DOP (10 in your example). DOP has absolutely no meaning in street navigation, and can only be of some limited value for geocaching. Recommendation: ignore, use default settings.
_________________
Lutz

Report Map Errors here:
TomTom/TeleAtlas NAVTEQ

[Quantum]

You are good Lutz, but in this case I don't think you've got it.

You're probably referring to the 'snap-to' that street nav software does. But if inaccurate info is fed into TomTom, it sure is not going to make it better, as I found the other day when it was 75' off. That is unacceptable error. There are other times when TomTom has me sailing off an exit, only to have it change its mind and then insist that I merge back on, in very heavy traffic.

Inaccurate in... worse inaccurate out. I realize that it is the orthodoxy to poo poo WAAS/EGNOS, but I don't buy it. I am confident that WAAS works better than either EGNOS bird, as it's been in operation longer, and is used for mission-critical things.

As to DOP, I've now found this:
"Particularly in indoor and dense urban scenarios, DOP has a major impact on accuracy. A number measuring the relative geometry of visible satellites, DOP helps determine the amount of error in position determination, and has a multiplier effect on position errors. The better the satellite geometry - generally, the more widely spaced visible satellites are - the better the accuracy. Correlatively, the more of the sky that is visible, the better the accuracy (and the converse as well)."

I have now set all the relevant parameters which I think are best in my 236, and have a DGPS 3D lock 80% of the time in this forested area, and so am looking to find a geo-referenced slug somewhere around here, so I can test. Actually, I have found one at Sandy Point on Lake WA, but only have the NAD83 coordinates (not the WGS84). Found shareware to convert, but I run Debian.

And unfortunately I cannot use SA Watch, as I run Linux and don't have bluetooth anyway in my notebook, but at least I'll have a good idea of accuracy if I can get converted to WGS84.

Wish I knew of a good screenshot program for the IPaq.

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