Re: calibration of bay area sensors

From: emanon (
Date: Tue Jun 16 1998 - 00:14:21 PDT

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Date: Tue, 16 Jun 1998 00:14:21 -0700
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Subject: Re: calibration of bay area sensors
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Bob Prevett wrote:
> To the folks at Call of the Wind,
> Let first me say that I am a relatively satisfied COTW customer. However, it seems
> that several of the Bay area sensors are not very well calibrated, thus decreasing
> their usefulness. So, below are some ideas on how to better calibrate the COTW sensor
> based on observations from windsurfers on the email list.
> Natural Bridges:
> The NB COTW sensor is way low, typically 8 to 10 mph below the actual wind on the
> water. A good way to calibrate this sensor would be to look at the Long Marine Lab
> sensor data. The site is at:
> Take a look at the "Two Hour Winds" report. It is very accurate and seems well
> calibrated with the actual wind on the water. An even better solution would be to
> somehow use this data directly instead of the COTW sensor data, if that could be
> arranged. Or, moving the COTW sensor to a position closer to this Long Marine Lab
> sensor would work, too.
> San Luis Resvr:
> The San Luis readings seem to be around 10 mph lower that the wind on the water when
> it's blowing there. The wind readings from the Park windtalker, 209-826-9019, are
> closer to the real wind on the water; these readings are approximately 4 mph under the
> real wind on the water. So, a good first step would be to use this park windtalker to
> better calibrate the COTW sensor. Or, moving the COTW sensor closer the Park sensor
> would work as well.
> 3rd Avenue:
> This sensor has always been well below the wind on the water. Potential solutions
> would be to move the sensor to a golf net pole closer to the launch site, put the
> sensor on the roof of that new building going up near the 3rd Ave site, or somehow put
> a sensor near the middle span of the San Mateo Bridge.
> Sherman Island:
> Based on input from people who have sailed at the Access or Powerlines this season,
> this sensor appearts to be about 5-7 mph low on days it blows there.
> Regards,
> BobP
> PS - If any other wind_talk'ers out there have additional/different wind site
> calibration data or ideas, please send it to COTW so that we can help them make their
> sensors even more useful for us.


your observations are really useful. but it seems to me that cotw is
doing a good job while facing hostility caused by wind withdrawal
syndrome. during a normal season you look at cotw's numbers and add your
own bias (negative or positive) based on wind direction. but this year
the problem is lousy wind, not numbers. it's every sailor's
responsibility to read the weather based on his or her own expertise and
to decide wheather to sail and what equipment is appropriate. cotw is a
good tool, nothing more. like any tool, you have to learn how to use it.

i wish we could find a service that would guarantee 20 mph nw for
$20/month. until then i sit here with the shakes...



I was beginning to feel like a machine. That's no way for a man to feel.

John Shaft

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