[Loadstone] 2 requests: move point and reconnect

Shawn Kirkpatrick shawn at odyssey.cm.nu
Tue Apr 10 02:49:00 BST 2007


I'll try to address both your points. First, I don't think that moving a 
point would help your problem very much. There's at least two factors 
effecting this. The first is the accuracy the point was saved with. The 
second is the accuracy of your gps receiver at the current time. Let's 
assume a perfect point accuracy for the moment and deal with the receiver 
accuracy. There are several conditions that'll effect this, the number of 
satellites, surrounding buildings etc. No matter what you do you'll still be 
subject to the gps drift when standing still. If your receiver is waas/egnos 
capable and you get a differencial gps fix then this drift can go down to as 
low as one metre. Otherwise, around 10 metres of drift is about normal. You 
could test this by standing still and hitting the select key to see how much 
the closest point drifts. Some receivers are better for this than others. 
Taking all this in to account moving a point probably won't fix things much. 
You could move a point 10 metres one way and it might be accurate for that 
moment but then it's just as likely to drift 10 metres the other way 30 
seconds later. When you're on the move this situation should be a lot better 
since the drifting isn't as much of a problem.
The disconnecting problem could be a bit tricky. The clock tick logic was 
implemented because some receivers when there batteries die can get to a 
point where the receiver isn't sending gps data but can still keep the 
bluetooth connection open. To fix this loadstone will disconnect if it 
hasn't heard from the receiver in over 5 seconds. In normal opperation this 
isn't a problem, normally the receiver will send data once per second. If 
your receiver is getting in to a state where it's sending data slower than 
that then this might be causing it to disconnect. This might also account 
for your accuracy problems if the data isn't caught up to where you actually 
are. Maybe the receiver has some kind of power saving mode? You'd have to 
look up information on that unit to find out if that's the case. If that's 
the case then it would be good to turn that mode off. There's a couple other 
situations where the receiver can be disconnected. The first is during long 
searches with the find point function. This is a bug and at some point that 
searching system is going to get a rewrite to hopefully fix things like 
this. The other reason the receiver can disconnect is if you're in an area 
with a lot of rf interference. This can be an area with a lot of computer 
equipment, other bluetooth devices, or something else generating radio 
interference that knocks out the connection. There's not a whole lot you can 
do in that situation. If the gps disconnects consistantly in an area then 
this is probably the reason. The only thing you might be able to do in that 
case is move the receiver closer to the phone. Another problem could be 
glitches in the bluetooth implementation in your phone or gps receiver. 
Nokia is well known for breaking things in there bluetooth implementations. 
In that case a firmware upgrade for the phone might help.
As to what can be done to fix this problem, maybe a few tweaks to the timing 
logic, maybe increasing the timeout to 10 seconds might work. I don't think 
trying to write a command to the receiver would be a good idea. If it really 
has disconnected then the program could end up in a long wait trying to 
write resulting in a write failure at the end. If the battery is dying but 
the bluetooth connection is still open then the write might appear to go 
through but have no effect. If the receiver has entered a low power state of 
some kind then a hot start may or may not bring it out of that mode. For 
that case a better solution would be to figure out how to get the receiver 
not to go into that mode in the first place. Trying to reconnect might work 
but presents its own problems. If the gps really is disconnected then you 
end up with a long wait and a connection error. The other problem is it 
seems to take a while for the phone to register the fact that a bluetooth 
connection really is gone. This isn't only happening for loadstone, on my 
n70 this happens for headsets and any other type of bluetooth connection. 
Trying to reconnect during this period results in an error. This seems to be 
phone dependant so would be kind of hard to work around.
Speaking of commands, you've probably noticed that none of the gps commands 
work with a gps receiver using the mtk chipset. This is a known issue, the 
commands are currently for the sirf chipset. We plan to implement a setting 
to set the chipset so the propper commands will get sent.

On Mon, 9 Apr 2007, R. Neill Hadder wrote:

> Hi guys,
>
> A 2-item wish list:
> 1) it seems like it would be possible to implement a "move current point"
> feature to help counteract the tendency to be say 10m off when you're
> walking along setting waypoints and then another 10m off, possibly the other
> direction, when you're going back through.  I constantly wish I could just
> "fix" a point, literally, when I find myself on the wrong side of the street
> from what the unit was reporting should be the case: 3 o'clock is as likely
> to really be 9:00 as not, within 12 meters, and only trigonometrically
> better at greater distances.  I'm sure moving a point x meters in a cardinal
> direction or clockface orientation translates into some decimal value of
> milliseconds in the coordinates.  I have a hunch that a little routine to
> accept input and make this calculation could double the tracking accuracy.
> Discussion welcome.
>
> 2) As I noted in my comments on the i-blue 737, there's some fairly common
> if not random condition that prompts the gps receiver to stop sending data
> to the phone, even though it's still actively tracking umpteen satelites.
> Loadstone disconnects, but can reconnect within a couple of seconds. I would
> like to try a setting that allows loadstone to try an automatic hot start
> before disconnecting.  Even if it's a low battery or low bluetooth signal
> issue, this would be helpful.  Invariably, the one time that I really need
> it in a high-traffic urban environment, the gps will go out and I am stuck
> fiddling with things, possibly for a prohibitive period of time.  Seems like
> it's worth a try.  Again, my own experience is with the 6682 and mtk.
>
> Gracias.
> --Neill
>
>
>
>
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