tag:blogger.com,1999:blog-4237678261594285909.post2643985263841309586..comments2024-01-05T22:40:53.671-05:00Comments on Sailboat Instruments: Compass calibration on the waterUnknownnoreply@blogger.comBlogger8125tag:blogger.com,1999:blog-4237678261594285909.post-37520096217005158542019-03-09T03:57:44.037-05:002019-03-09T03:57:44.037-05:00Thnq for sharing Informative news The Vasthi Wate...Thnq for sharing Informative news The Vasthi <a href="http://www.vasthi.com/water-analyzer/" rel="nofollow">Water analyzer</a> quality testing equipment is designed to give you field-ready durability with accurate results you can trust.snehahttps://www.blogger.com/profile/13600392721985814395noreply@blogger.comtag:blogger.com,1999:blog-4237678261594285909.post-45186542396770687542013-03-22T18:01:15.609-04:002013-03-22T18:01:15.609-04:00Here is the NLREG input file that will calculate t...Here is the NLREG input file that will calculate the coefficients for the simplified example in this post. Open this in NLREG, run, and you will get the following coefficients:<br /><br />A 9.8714987<br />B -6.57413958<br />C 6.37813634<br />D 0.33566988<br />E 2.2953011<br />___________________________________<br /><br />Title "Deviation Coefficients";<br />Variables X, Y;<br /><br />TOLERANCE 1E-12;<br />ITERATIONS 1000;<br /><br />/*<br /> * Definite parameters to be calculated.<br /> * Specifying reasonable starting values greatly increases the chances for convergence.<br /> */<br />Parameter A = 10; <br />Parameter B = 0; <br />Parameter C = 0;<br />Parameter D = 0; <br />Parameter E = 0; <br /><br />/*<br /> * Work variables.<br /> */<br />double theta;<br />double dtheta; <br />double Norm; <br />double Deviation;<br /><br />/*<br /> * Compute the expected heading.<br /> */<br /> <br /> theta = X*3.14159/180.0;<br /> dtheta = theta * 2.0;<br /> Norm = A + B * sin(theta) + C * cos(theta) + D * sin(dtheta) + E * cos(dtheta);<br /><br />/*<br /> * Compute the deviation.<br /> */<br /> Deviation = (Y - Norm) * (Y - Norm);<br /><br />/*<br /> * Minimize the sum of squared deviations.<br /> */<br /> Function Deviation;<br />/*<br /> * X, Y data values.<br /> */<br /><br /> Data;<br /><br />100.0 0.0<br />117.9 -0.1<br />137.0 1.0<br />156.9 2.9<br />177.1 5.1<br />197.4 7.4<br />217.5 9.5<br />237.5 11.5<br />257.4 13.4<br />277.2 15.2<br />297.0 17.0<br />316.4 18.4<br />335.2 19.2<br />353.1 19.1<br />369.7 17.7<br />25.1 15.1<br />39.6 11.6<br />53.8 7.8<br />68.2 4.2<br />83.5 1.5<br />Merlinhttps://www.blogger.com/profile/00901116173524809046noreply@blogger.comtag:blogger.com,1999:blog-4237678261594285909.post-91606496294384785382013-03-19T12:14:03.187-04:002013-03-19T12:14:03.187-04:00Hi
Thanks for a great blog.
I have a question to...Hi<br /><br />Thanks for a great blog.<br /><br />I have a question to how you find the 5 deviation coefficients (A, B, C, D, E). <br /><br />How is this done in NLREG or a similar program. Do you have link?<br /><br />MartinMartinnoreply@blogger.comtag:blogger.com,1999:blog-4237678261594285909.post-37511182089234359182012-08-29T21:21:05.310-04:002012-08-29T21:21:05.310-04:00Well, the story is as follows. After installing th...Well, the story is as follows. After installing the H2183 on the boat, I went through the manufacturer calibration procedure, using the WeatherCaster software on a laptop. The procedure reported a success, but the result was truly bad. So, before doing the test described here, I used the WeatherCaster software to bring the compass back to manufacturer default values, but I don't know if it really did that, or if it kept the defective calibration. Even if I don't know the real starting point, the procedure described in this post has corrected the situation, as both compasses now agree after calibration.<br /><br />The boat has a steel keel, and the deviation curves have the expected signature for this situation. Merlinhttps://www.blogger.com/profile/00901116173524809046noreply@blogger.comtag:blogger.com,1999:blog-4237678261594285909.post-66451165845802470132012-08-29T20:44:06.833-04:002012-08-29T20:44:06.833-04:00Is the curve above for an H2183 that has been thro...Is the curve above for an H2183 that has been through the manufacturer defined calibration procedure?Grady Morganhttp://nanoreply@blogger.comtag:blogger.com,1999:blog-4237678261594285909.post-83956544256258821822012-08-16T11:21:18.038-04:002012-08-16T11:21:18.038-04:00ah - of course. I suppose the solution would be to...ah - of course. I suppose the solution would be to speed up the turn. If your deviation is, say, max 20deg=360deg/18 and your rate-gyro sensitivity is 1deg/s you need to be turning at least (360deg/18)/s=20deg/s. Mh. I probably can do that in my Laser or even trimaran. Not sure about the oil tanker ...DrSARnoreply@blogger.comtag:blogger.com,1999:blog-4237678261594285909.post-60082603107688701652012-08-16T01:03:40.567-04:002012-08-16T01:03:40.567-04:00In principle, yes.
But this would require an extr...In principle, yes.<br /><br />But this would require an extremely sensitive and accurate gyro. Making one turn in 3 minutes gives 2 deg/s. For the Airmar H2183, the Rate-of-Turn Accuracy is 1 deg/s, far from an acceptable precision for such a task. The H2183 Rate-of-Turn output values are also very noisy.<br />Merlinhttps://www.blogger.com/profile/00901116173524809046noreply@blogger.comtag:blogger.com,1999:blog-4237678261594285909.post-47808924567660406422012-08-15T20:45:11.812-04:002012-08-15T20:45:11.812-04:00Maybe I am not understanding this properly: In a p...Maybe I am not understanding this properly: In a previous post you asserted that you "came to the conclusion that a gyro is not needed in a marine compass, as the rate of turn can be calculated from the calibrated output of a fast compass." That maybe so. But wouldn't the calibration be easier since a rate gyro could provide the turn that occurred which you can compare to the turn as per compass to figure your deviation? This should relax your requirement to having to perform a turn at constant rate of turn, no?DrSARnoreply@blogger.com