SiRF III: is sensitivity better than accuracy?

No, the SiRFDemo program will not work with this unit. At least I
have not figured out how to do that. It has a control to put the
receiver in binary mode, but it does not let you control any of the
command parameters. This control appears to change the baud rate to
57600 (the data source setup changes to 57600). I believe this sets
the rate on the SiRF chip to 57600, but the Holux bluetooth chip does
not know the rate has changed and remains at 38400. The result is the
unit sends out garbage and will no longer respond to commands. Then I
have to let the battery drain for this to reset.



Yup! I had a Magellan Merigold that would pick up WAAS very easily
and report location error estimates down to 7 feet! Unfortunatly the
screen died and it is no longer usable.

I continued with my tests today and I did find a way to put the Holux
240 into binary mode. I used a tool called NMEA GPS Monitor. It
allows you to send and receive binary commands without trying to
understand or interpret them. It does have the great feature of
calculating check sums however!

So I put the Holux 240 into binary mode and received valid SiRF status
messages. I sent this command to select the DGPS source as SBAS
satellite. It still reports that DGPS is *not* using differential
corrections.

Just to verify everything I said about SiRFDemo, I ended up putting
the receiver into the corrupt state and I have to wait for the battery
to drain. When it comes back up I will try some more tests to see if
I can get DGPS WAAS to work.

With all the problems I have had trying to get this working (not to
mention an issue with a dispreputable eBay seller who sent me a broken
Palm) I have not geocached in three weeks. I am getting tired of
playing with the gadgets and would like to be able to use the durn
things!!!

BTW, NMEA GPS Monitor is a *GREAT* programfor the PC!!! It not only
provides this excellent communications mode, it displays a lot of data
(NMEA only of course, read the name) and is FREE! It is not available
for PDAs or I would just use that on the palm. It is not open source
or I would port it!!!

: BTW, NMEA GPS Monitor is a *GREAT* programfor the PC!!! It not only
: provides this excellent communications mode, it displays a lot of data
: (NMEA only of course, read the name) and is FREE! It is not available
: for PDAs or I would just use that on the palm. It is not open source
: or I would port it!!!

It (NMEA GPS Monitor) seems to only support the Serial interface and
not USB?

Yes, it looks that way. With a bluetooth interface, the bluetooth
drivers emulate a serial port. Does USB do the same thing?

On 10 May 2007 07:17:56 -0700, nemo wrote:


I have the same on my Holux 236. However, I only wanted to try it...


Sorry, I need to disagree. Most cases the track is in sync with the
road and offroad maps I have, in a ~5m radius. What else would I need?
I am not going to touch down a plane using that, I am following a road
and have other senses at my head.

And in those cases where the reception is not good enough to have good
accuracy, there would for sure not be any augmentation service
available or the signal would be useless as it is not constructed to
correct errors from reflection but from run time changes in the
athmosphere.

I had it on my Map76S before, and turned it on to see if it works, and
then turned it off again....
--

Ciao,
Holger (GUS-KOTAL, GUS#1100)

90-92 Honda CB400 10 Mm | 93-95 Yamaha TDM 850 26 Mm
95-97 KTM 620 LC4 13 Mm | seit 97 BMW R1100GS 50 Mm (Die Renndrecksau!)

cu @ http://www.issle.de

nemo wrote:
[snip]

The sensitivity means it will work in urban canyons for road
navigation. If it's off by sixty feet, it probably doesn't matter.
The user will get the travel directions needed.

The sensitivity means it picks up multipath that will make it
somewhat poorer in accuracy but does produce a position
solution as opposed to none at all. Loss of lock tends to
upset your casual user, especially when trying to get
somewhere in a city.

I don't have a lot of experience with the SiRF III yet, but
I've seen a Garmin GPSmap 76S produce a relatively more
accurate track receiving four satellites in a poor pattern
in a mountain canyon than a GPSmap 76Cx receiving eight
satellites. Four of those were not directly visible so
the 76S didn't receive them but it looked like the 76Cx
picked up bounced signals which resulted in a less accurate
track. For most users it wasn't off far enough to matter.

If you really want accuracy, you don't want to pick up
multipath signals.

--
Dan
(email change 2001 to 2004)
(www.gpsmap.net)