Hi Dan, Sorry for the delay in replying.
>From a PRACTICAL point-of-view, as we all know, analogue watches replaced >sundials, digital watches replaced analogue watches, and smart phones have >replaced watches. Digital compasses replaced analogue compasses, and now smart >phones have replaced compasses. I confess to having a mobile phone, and no >longer wearing a watch. Also when I go bushwalking, now I carry a GPS with >real-time tracking on appropriate-scale topographic maps. I still have a >digital compass, but it was pretty fiddly to use, so it now sits somewhere at >home. I only use a magnetic compass when doing serious field work, and I need >to know the orientation of some feature I am measuring. But what has practicality to do with anything related to sundials???? Several years ago I was also intrigued about the accuracy of using a watch as a compass, and I decided to investigate it the empirical way. So I made up a little “tool” and every weekend when I went bushwalking, I would set it up and compare compass north with watch north at regular intervals. I ended up with quite a few measurements before life got in the way of plans, and the project petered out. I still have the results but I have never analysed them. In part because even then it was obvious to me that the question could be investigated using standard equations. But my feeling at the time was that the whole watch / north method was getting close to an urban myth. I had collected several variations on instructions, but I seem to have lost them in one of my several moves. But I do remember that depending on which you used, the error could be 30o or more. None of the methods said anything about the difference between true and magnetic north, but that may be irrelevant anyway unless you are somewhere like Antarctica where the difference can be 70o. More important would be DST which could be a major trap for the unwary. At one stage the watch / north method was called the “Boy Scout”method. During my travels on public transport when kids are going to school, I haven’t seen too many wearing analogue watches. Or watches of any form. They are completely welded to their smart phones, so it’s pretty obvious that the method has gone the way of sundials. When you find the analysis of the watch / north idea, can you post it on the List please? Cheers, John John Pickard [email protected] From: Dan-George Uza Sent: Saturday, September 29, 2018 4:57 AM To: Sundial List Subject: Accuracy of wristwatch as compass Hello! I'm sure you know the method of pointing the analogue wristwach hour hand towards the Sun and then bisecting the angle to 12 o'clock in order to find south (or north, if you live down in the south). Actually I guess what you should be doing is bisect the angle to your noon time and not necessarily 12 o'clock, but anyway. A few years ago I read an interesting seasonal accuracy analysis of this method. I also vaguely remember the demonstration involved Vitruvius' analemma and I'm pretty sure it was all in a book. Thing is - I can't remember where! Can you help? Dan Uza -------------------------------------------------------------------------------- --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
--------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
