Tim,
Does a lap potentially include a figure 8? You will be on the same heading
twice per lap in a figure 8, but you could monitor the sweep of headings to
capture that possibility. Maybe a lap requires a reasonable progression through
southern, eastern, northern, and western headings.
--WS
Message: 3
Date: Sun, 15 Jan 2012 13:08:18 -0500
From: Thomas McGrath III <mcgra...@mac.com>
To: How to use LiveCode <use-livecode@lists.runrev.com>
Subject: Determine 180 degree turn using compass
Message-ID: <3b55c011-6a6a-4529-9d17-e218155e2...@mac.com>
Content-Type: text/plain; CHARSET=US-ASCII
OK, this is for the math experts here.
Using a working Compass app I would like to determine when the phone is turned
around from an initial starting point. So I am working out the best ways to do
this.
1. Start by capturing the start heading
2. Store that in a global
3. Store that the start heading has been set
4. Using headingChanged capture the currentHeading at intervals
5. Check the new currentHeading against the start heading
6. If enough of a difference is detected then count that as a lap
7. Set the new currentHeading as the global heading
8. Using headingChanged capture the currentHeading at intervals
9. Repeat until stopped
10. return total lap count
So this seems straight forward (if I haven't missed anything)
And if I start at 10 degrees and turn right 170 now I am at 180. Good. I just
subtract 10 from 180 and I know I have turned at least 170 degrees and can
count that as a lap (give or take)
BUT then the new starting point may not be right since I might be mid turn when
the interval fires.
And if the starting point is say 10 and I turn left 170 degrees and now I am at
200 and 10 - 200 is -190 but I have not really turned -190 but only 170 and
again this may be incorrect based on when the sample interval was fired.
So, It looks to me like I need to come up with a better way to estimate the
general direction I am starting from and a better way to set the intervals. As
well as figuring out the right way to handle the compass degrees when they pass
0/360.
I have never had to do this before and would like some advice and feedback on
what/how to get there.
So far I started with this code after starting the compass heading capture:
global myLapCountNumber
on headingChanged
put iphoneCurrentHeading() into tHeading
lapCount tHeading["heading"]
end headingChanged
on lapCount pNum
if pNum is not "" then
if myLapCountNumber is not "" then
if pNum > myLapCountNumber then
if pNum - myLapCountNumber > 150 then
answer pNum && "-" && myLapCountNumber && "= Lap Right +"
put pNum into myLapCountNumber
end if
else -- pNum is less than myLapCountNumber
if myLapCountNumber - pNum > 150 then
answer myLapCountNumber && "-" && pNum && "= Lap Left -"
put pNum into myLapCountNumber
end if
end if
else
put 0 into myLapCountNumber -- Needs changed to a sampling of the
general direction
end if
end if
end lapCount
-- Tom McGrath III
http://lazyriver.on-rev.com
3mcgr...@comcast.net
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