RE: Another Sundial with VI at Midday...
Dear Frank, I have only just got around to reading your account of the Margaret Stanier Memorial Dial which I downloaded a couple of weeks ago so I hope you will treat this response as better late than never. Congratulations on implementing a novel dialling concept in such a beautiful dial. Your account of the evolution and manufacture of the dial was a delight to read and I am surprised that it has not resulted in more widespread acclaim from this list. I must assume that your readers are dumbfounded. My only comment is that your omission of the sunrise/sunset hours should be regarded as of no practical disadvantage since the timings of these phenomena are evident to the observer without the need for a dial. You asked to be alerted to typos and I think that you might have transposed the standard deviation values for R1 and R2 in the last sentence of the penultimate paragraph on page 30. Thank you for providing us with such a comprehensive and thought-provoking account of your creation. Best Wishes, Geoff -Original Message- From: sundial-boun...@uni-koeln.de [mailto:sundial-boun...@uni-koeln.de] On Behalf Of Frank King Sent: 26 September 2010 17:18 To: sundial Subject: Another Sundial with VI at Midday... Dear All, The beer-glass sundial spotted by Mike Cowham brought on a panic attack. More strictly, it was his comment that caused alarm... The glass acts as the gnomon but the real horror ... midday was at VI. Maybe every reader should pour a glass of beer (or something stronger) before reading any further. I have just inaugurated my latest creation and, guess what, midday is at VI. Should I spend my declining years designing sundials for garden centres? Make sure you have a first-aider to hand and take a look at: http://www.cl.cam.ac.uk/users/fhk1/Newnham/FHK+Dial.jpg I hope, by the way, that you like my outfit. I chose to wear British Sundial Society-approved colour-coordinated yellow for the occasion. This sundial is a memorial tribute, by Newnham College, Cambridge, to Margaret Stanier, lately Editor of the BSS Bulletin. About 10 years ago, Margaret told me how important mass dials were so I thought I would come up with a design which is (ever so loosely) based on a 24-line mass dial. My goal was impossible but I am not easily put off... I wanted an unequal-hours sundial where the time is indicated by the direction of the shadow of a rod gnomon. [I didn't want to use a nodus and its point-indicating shadow.] Is there a best approximation? Newnham College asked for a account written for technically-minded academics who know nothing about sundials. You can see this, and numerous photographs, at: http://www.cl.cam.ac.uk/users/fhk1/Newnham/write-up.pdf You will even see that this dial incorporates a few dialling jokes :-) Here I proffer some acknowledgements to: Margaret Stanier for the inspiration. Frans Maes and many others for making me think about the Braunschweig dials. Geoff Thurston for making me think about just what is meant by best-fit when making compromises. Gianni Ferrari for explaining that the hour-lines on this design don't have great gnomonic meaning. Not many unequal-hours sundials get made these days so, if you think it is a sundial at all, make the most of this one :-) Please let me know of all the typos that you spot. I haven't handed the account to the College yet! Now what was that beer that Mike was telling us about? Frank H. King Cambridge, U.K. --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Light Based Geolocation
Hi: This is a little off topic, but bears a strong relation to sundials. After watching a TED talk on taging of tuna with sensors that determined the Lat and Lon of the fish based on the length of a day and the time of sunrise and sunset I found this method is called Light Based Geolocation. I'd like to learn more about what data the tags store and how smart they are. For example is there a micro controller in the tag that make computations or is it just a data logger? -- Have Fun, Brooke Clarke http://www.PRC68.com --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Light Based Geolocation
In a similar vein, it's just been on the news in the UK that we've learned more about the migration of nightingales from one tagged individual than all previous studies put together. The bird's tag recorded only the time and date of nightfall and daybreak. From this the route from England to Africa via Gibraltar was deduced. See http://dearkitty.blogsome.com/2010/06/29/nightingale-migration-discoveries/ Apparently, the tags were developed for tracking albatrosses. They can't transmit the data, but must be recovered. So the processing power on board would seem to be pretty primitive. Birds, I can understand, but I'm surprised it works for fish. Perhaps tuna never dive too deep. Chris Lusby Taylor - Original Message - From: Brooke Clarke brooke95...@att.net To: 'sundial' sund...@rrz.uni-koeln.de Sent: Tuesday, October 12, 2010 5:54 PM Subject: Light Based Geolocation Hi: This is a little off topic, but bears a strong relation to sundials. After watching a TED talk on taging of tuna with sensors that determined the Lat and Lon of the fish based on the length of a day and the time of sunrise and sunset I found this method is called Light Based Geolocation. I'd like to learn more about what data the tags store and how smart they are. For example is there a micro controller in the tag that make computations or is it just a data logger? -- Have Fun, Brooke Clarke http://www.PRC68.com --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Light Based Geolocation
Hi Brooke, Here's a description of a light based geolocation capable tag. http://www.wildlifecomputers.com/Products.aspx?ID=20 Geolocation using light-level Wildlife Computers has developed software, WC-GPE, that calculates daily longitude and latitude from recorded light level curves. Longitude accuracy can be as good as ±0.5 degrees. Latitude accuracy depends upon both the latitude and time of the year. Best accuracies (±1 degree) are achieved at high latitudes near the solstices, and worst occur near the equator near the equinoxes (±10 degrees, where and when latitude can be calculated). A much more detailed explanation of the computation is in the appendix of their users manual. http://www.wildlifecomputers.com/Downloads/Documentation/WC-GPE%20Suite%20Manual.pdf This solar based method is typically used if the animal is not likely to surface often and or there is a power budget concern. What's surprising is that this method can work, based on water clarity, down to 200m+ (limits of the euphotic zone). http://nicholelyons.tripod.com/ Location tags requiring higher accuracy are now using this method: http://www.wildtracker.com/fastloc.htm Luke On 10/12/2010 9:54 AM, Brooke Clarke wrote: Hi: This is a little off topic, but bears a strong relation to sundials. After watching a TED talk on taging of tuna with sensors that determined the Lat and Lon of the fish based on the length of a day and the time of sunrise and sunset I found this method is called Light Based Geolocation. I'd like to learn more about what data the tags store and how smart they are. For example is there a micro controller in the tag that make computations or is it just a data logger? --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Light Based Geolocation
So I am marooned on a island with nothing but I might be able to determine a few things that I could write on a message in a bottle that would help my rescuers determine my exact location. By careful sunrise observation I could determine the solstices. Now I have a calendar. I know dawn to dawn is 24 hours so I could make a clock with a washed up bottle filled with sand and measure/mark what comes out in one day. Then I could cut that sand in half for 12 hours and half again for 6 hours and half again for 3 hours and then thirds for one hour. Now I have an hour clock. Now I can measure the hours of daylight from dawn to dusk on the solstice and send that in the bottle and my rescuers will be able to determine my latitude and longitude. Of course I would have to say northern or southern solstice but that's easy because we know the sun rises in the east. Would this be enough information? thanks again; brent --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Light Based Geolocation
Brent, I think you could determine your latitude this way, but not your longitude. For the longitude, you would need some way to relate your local sunrises and sunsets to the local time at some known longitude, such as that of Greenwich. In other words, the geolocation tagging gadget must carry a time-of-day clock from a known longitude. This is the same as the age-old longitude problem that all mariners faced. -- Roger - Original Message - From: Brent bren...@verizon.net To: Sundial List sund...@rrz.uni-koeln.de Sent: Tuesday, October 12, 2010 5:05 PM Subject: Re: Light Based Geolocation So I am marooned on a island with nothing but I might be able to determine a few things that I could write on a message in a bottle that would help my rescuers determine my exact location. By careful sunrise observation I could determine the solstices. Now I have a calendar. I know dawn to dawn is 24 hours so I could make a clock with a washed up bottle filled with sand and measure/mark what comes out in one day. Then I could cut that sand in half for 12 hours and half again for 6 hours and half again for 3 hours and then thirds for one hour. Now I have an hour clock. Now I can measure the hours of daylight from dawn to dusk on the solstice and send that in the bottle and my rescuers will be able to determine my latitude and longitude. Of course I would have to say northern or southern solstice but that's easy because we know the sun rises in the east. Would this be enough information? thanks again; brent --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Light Based Geolocation
The way I understand the geolocation device is that dawn rises at the same time along different longitudes. If you know what time sunrise is and how long the day is on a particular day you know your latitude as well as your longitude. On a deserted island, the time of sunrise is the number of hours before high solar noonand maybe half way between sunrise and sunset. This manual seems to indicate these concepts: http://www.wildlifecomputers.com/Downloads/Documentation/WC-GPE%20Suite%20Manual.pdf It's because of the tilt of the earth? Roger W. Sinnott wrote: Brent, I think you could determine your latitude this way, but not your longitude. For the longitude, you would need some way to relate your local sunrises and sunsets to the local time at some known longitude, such as that of Greenwich. In other words, the geolocation tagging gadget must carry a time-of-day clock from a known longitude. This is the same as the age-old longitude problem that all mariners faced. -- Roger - Original Message - From: Brent bren...@verizon.net To: Sundial List sund...@rrz.uni-koeln.de Sent: Tuesday, October 12, 2010 5:05 PM Subject: Re: Light Based Geolocation So I am marooned on a island with nothing but I might be able to determine a few things that I could write on a message in a bottle that would help my rescuers determine my exact location. By careful sunrise observation I could determine the solstices. Now I have a calendar. I know dawn to dawn is 24 hours so I could make a clock with a washed up bottle filled with sand and measure/mark what comes out in one day. Then I could cut that sand in half for 12 hours and half again for 6 hours and half again for 3 hours and then thirds for one hour. Now I have an hour clock. Now I can measure the hours of daylight from dawn to dusk on the solstice and send that in the bottle and my rescuers will be able to determine my latitude and longitude. Of course I would have to say northern or southern solstice but that's easy because we know the sun rises in the east. Would this be enough information? thanks again; brent --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Light Based Geolocation
Hi Brent, Would that it were that simple. Longitude still requires an absolute, not relative time fix. You still need to know the time and longitude from Greenwich. Sunrise and noon are relative to local time. Discovering longitude for many years perplexed astronomers and navigators to the point of insanity. Dava Sobel's book Longitude is a great read. Roger Bailey -- From: Brent bren...@verizon.net Sent: Tuesday, October 12, 2010 2:59 PM To: Roger W. Sinnott rsinn...@post.harvard.edu; Sundial List sund...@rrz.uni-koeln.de Subject: Re: Light Based Geolocation The way I understand the geolocation device is that dawn rises at the same time along different longitudes. If you know what time sunrise is and how long the day is on a particular day you know your latitude as well as your longitude. On a deserted island, the time of sunrise is the number of hours before high solar noonand maybe half way between sunrise and sunset. This manual seems to indicate these concepts: http://www.wildlifecomputers.com/Downloads/Documentation/WC-GPE%20Suite%20Manual.pdf It's because of the tilt of the earth? Roger W. Sinnott wrote: Brent, I think you could determine your latitude this way, but not your longitude. For the longitude, you would need some way to relate your local sunrises and sunsets to the local time at some known longitude, such as that of Greenwich. In other words, the geolocation tagging gadget must carry a time-of-day clock from a known longitude. This is the same as the age-old longitude problem that all mariners faced. -- Roger - Original Message - From: Brent bren...@verizon.net To: Sundial List sund...@rrz.uni-koeln.de Sent: Tuesday, October 12, 2010 5:05 PM Subject: Re: Light Based Geolocation So I am marooned on a island with nothing but I might be able to determine a few things that I could write on a message in a bottle that would help my rescuers determine my exact location. By careful sunrise observation I could determine the solstices. Now I have a calendar. I know dawn to dawn is 24 hours so I could make a clock with a washed up bottle filled with sand and measure/mark what comes out in one day. Then I could cut that sand in half for 12 hours and half again for 6 hours and half again for 3 hours and then thirds for one hour. Now I have an hour clock. Now I can measure the hours of daylight from dawn to dusk on the solstice and send that in the bottle and my rescuers will be able to determine my latitude and longitude. Of course I would have to say northern or southern solstice but that's easy because we know the sun rises in the east. Would this be enough information? thanks again; brent --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Light Based Geolocation
Hi Bailey: I live in Ukiah, California where one of the five Latitude observatories (all at 39 deg 08 min North) operated for almost 100 years starting around 1899. It turns out that finding the Latitude was a much harder problem to solve than finding the longitude. http://www.prc68.com/I/UkiahObs.shtml Have Fun, Brooke Clarke http://www.PRC68.com Roger Bailey wrote: Hi Brent, Would that it were that simple. Longitude still requires an absolute, not relative time fix. You still need to know the time and longitude from Greenwich. Sunrise and noon are relative to local time. Discovering longitude for many years perplexed astronomers and navigators to the point of insanity. Dava Sobel's book Longitude is a great read. Roger Bailey -- From: Brentbren...@verizon.net Sent: Tuesday, October 12, 2010 2:59 PM To: Roger W. Sinnottrsinn...@post.harvard.edu; Sundial List sund...@rrz.uni-koeln.de Subject: Re: Light Based Geolocation The way I understand the geolocation device is that dawn rises at the same time along different longitudes. If you know what time sunrise is and how long the day is on a particular day you know your latitude as well as your longitude. On a deserted island, the time of sunrise is the number of hours before high solar noonand maybe half way between sunrise and sunset. This manual seems to indicate these concepts: http://www.wildlifecomputers.com/Downloads/Documentation/WC-GPE%20Suite%20Manual.pdf It's because of the tilt of the earth? Roger W. Sinnott wrote: Brent, I think you could determine your latitude this way, but not your longitude. For the longitude, you would need some way to relate your local sunrises and sunsets to the local time at some known longitude, such as that of Greenwich. In other words, the geolocation tagging gadget must carry a time-of-day clock from a known longitude. This is the same as the age-old longitude problem that all mariners faced. -- Roger - Original Message - From: Brentbren...@verizon.net To: Sundial Listsund...@rrz.uni-koeln.de Sent: Tuesday, October 12, 2010 5:05 PM Subject: Re: Light Based Geolocation So I am marooned on a island with nothing but I might be able to determine a few things that I could write on a message in a bottle that would help my rescuers determine my exact location. By careful sunrise observation I could determine the solstices. Now I have a calendar. I know dawn to dawn is 24 hours so I could make a clock with a washed up bottle filled with sand and measure/mark what comes out in one day. Then I could cut that sand in half for 12 hours and half again for 6 hours and half again for 3 hours and then thirds for one hour. Now I have an hour clock. Now I can measure the hours of daylight from dawn to dusk on the solstice and send that in the bottle and my rescuers will be able to determine my latitude and longitude. Of course I would have to say northern or southern solstice but that's easy because we know the sun rises in the east. Would this be enough information? thanks again; brent --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial -- Have Fun, Brooke Clarke http://www.PRC68.com --- https://lists.uni-koeln.de/mailman/listinfo/sundial
