[Xastir] Position rate possibility....

[Earl Needham via Kubuntu]

Richard Polivka, N6NKO wrote:
<snip>
> 1) Fixed position. If the vehicle drops below a certain threshold speed, 
> call it STOP SPEED, we send out a quick burst of packets, say three to 
> five , to show the speed coming to zero for at least two packets.

	I'm not sure we would want to do this, because every time you come to a 
red light, you'd be going through this procedure.  Some parts of the 
country can't take that.  Maybe ONE packet would be OK.

> 2) Moving mode. Me sees three possibilities here: A) fixed time 
> beaconing; B) Fixed distance beaconing; C) Speed based beaconing.  I 
> would prefer speed based beaconing. Instead of having threshold points, 
> I would make the time change linear. Have an X-Y formula: X being speed; 
> Y being distance. Both end points on both axes are settable. At slower 
> speeds, you usually are working city streets. This would require more 
> transmissions because of the Urban Canyon issue and there are more 
> opportunities to radically change course. This would avoid the big 
> position jump on a track where you look at a map and see someone halfway 
> across the county changing directions.

	The HamHUD used to send extra beacons in the event it didn't receive a 
digi repeating it's own signal.  It was taken out, I think because of 
other people complaining about channel congestion, but I'm not 100% sure 
of that -- it's been several years.

> 3) Dealing with turns. This seems to be a sore spot - corner pegging. We 
> only have a max data rate of 1 secoud out of most GPS units. So what I 
> would do is modify the sending rate based on the degrees turned and 
> instead of using a lookup table, I would use maybe cos^2 or cos^3 of the 
> angle change as the modfier. Modify from the current beaconing rate down 
> to 1 sec beaconing at >= 90 degrees. Here in Wisconsin, U-turns are 
> legal so those would have to be covered.
> 
> Now if I have covered old ground, forgive me. These are just thoughts.

	When I first got started with the HamHUD, I tried and tried to do 
perfect corner pegging, but I was never succesful.  The problem being 
that, in a 90-degree turn at an intersection, you need one set of 
parameters, but in a 90-degree sweeper at 70 MPH, you need an entirely 
different set of parameters.  I don't think slope is enough to get it 
right.  I used to get 2 or 3 position packets sent out in the sweepers, 
and while I could make adjustments to reduce that, it generally messed 
up the intersections.

	The other problem that I though I was seeing, but no one else agreed, 
was if I came to, say, a 20-degree bend in the road and I was travelling 
65 MPH, I did NOT get a position packet sent out.  I think I was told 
that, at those speeds, almost all the beacons are done by timing and not 
by turning.

	In the end, I just set everything to the default values and forgot 
about it.

	7 3
	Earl
-- 
Earl Needham KD5XB
Clovis, New Mexico DM84jk
ZUT