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rini:speed_log_notes [2009/04/17 05:05] ben |
rini:speed_log_notes [2009/04/17 06:37] ben |
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* For now it seems that traveling 1 mile and counting the number of transducer clicks will provide an adequate average result | * For now it seems that traveling 1 mile and counting the number of transducer clicks will provide an adequate average result | ||
* Once the number of clicks for 1 n. mile is found, math is Distance in n. mile divided by time in hours = Speed in knots, choose a very small unit of time to count clicks for to allow fast updates of speed calculation (2s?) | * Once the number of clicks for 1 n. mile is found, math is Distance in n. mile divided by time in hours = Speed in knots, choose a very small unit of time to count clicks for to allow fast updates of speed calculation (2s?) | ||
- | <tab><blockquote> | ||
- | Best I can get this described in ASCII: | ||
+ | Best I can get this described in ASCII: | ||
+ | <tab><blockquote> | ||
D = distance in nautical miles | D = distance in nautical miles | ||
+ | |||
T = time in hours | T = time in hours | ||
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S = speed in knots | S = speed in knots | ||
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X = Number of clicks counted while traveling a calibration mile | X = Number of clicks counted while traveling a calibration mile | ||
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Y = Number of clicks counted in a single sample period | Y = Number of clicks counted in a single sample period | ||
+ | |||
Z = Sample period in Seconds | Z = Sample period in Seconds | ||
D = Y/X * 1 n.m. | D = Y/X * 1 n.m. | ||
+ | |||
T = Z/3600 | T = Z/3600 | ||
- | So: (Z/X * 1 n.m.) / (Z/3600) = Speed in knots for the sample period Z | + | So: (Y/X * 1 n.m.) / (Z/3600) = Speed in knots for the sample period Z |
- | E.G. If we calibrate 1 n.m. at 2500 clicks (X=2500) and our sample/update period is 2 seconds (Z=2), and over that period we count 30 clicks (Y=30), then calculated speed would be (30/2500)/(2/3600) = S = 0.012 / 0.0011 = 1.0909 knots. | + | E.G. If we calibrate 1 n.m. at 2500 clicks (X=2500) and our sample/update period is 2 seconds (Z=2), and over that period we count 10 clicks (Y=10), then calculated speed would be (10/2500)/(2/3600) = S = 0.004 / 0.0006 = 6.67 knots. |
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+ | Hopefully we get faster turn rates that 5 rotations per second, otherwise it won't be very precise. | ||
</blockquote> | </blockquote> | ||
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