Hi Marcus: The people who can confirm the latest accepted or recently obtained results on Earth would be The National Geographic and Oceonography experts. The values I used were the latest available to me. Do let me have any NEW info, please! Brij Bhushan Vij <[EMAIL PROTECTED]>
>From: "Ma Be" <[EMAIL PROTECTED]> >Reply-To: [EMAIL PROTECTED] >To: "U.S. Metric Association" <[EMAIL PROTECTED]> >Subject: [USMA:21759] Re: Is the meter defined at sea level? >Date: Fri, 16 Aug 2002 15:03:46 -0700 > >On Sat, 17 Aug 2002 07:28:22 > Pat Naughtin wrote: > >Dear Marcus, Joe, and All, > > > >If I add Hayford's 'Equatorial circumference of the earth = 40 076.594 >km' > >and his 'Polar circumference of the earth = 39 941.028 km' and divide by >2, > >does this give me the mean circumference of the Earth? In this case it >would > >be 40 008.811 kilometres - or some 9 kilometres more than the original > >(1792) figure. > > >Thanks for the info, Pat. Now, I believe my question still has relevancy >since it's still unclear how one came up with the above values. Did the >authors consider earth's relief, sea level values, disregarded relief >altogether, calculated at some arbitrary meridian?... Until we know what >assumptions were used it's difficult to "check" the validity of the above >results. > >In any case, we could proceed to derive charts, cartography data, etc at >some arbitrary altitude (such as at my 560 m value). This should not be >such a pain for the community since we could quote altitudes at RL instead >of SL (Reference Level and Sea Level, respectively). No big deal, really. > > >BTW, Marcus, where did you get the number '560 m below sea level'? > > >Simple, I assumed that the "correct" value at sea level was 40003.52 km >(i.e. a value as quoted by another colleague here sometime ago). Found a >radius of 6366.758 km. Now subtract this value at a radius that would give >exacts 400000, i.e. 6366.198 and voil`, the value comes at 560 m below "sea >level" (if that's what was used to derive the "correct value"). If one >uses the nautical mile as referring to that (sea level), then the distance >becomes a convenient 500 m! (well, ok... 510, 511...). > >The principle behind this calc could apply to any other value that is >deemed to be the "sea level" one. Whatever the spherical difference in >altitude this would become the RL where 0.01 gr would be exacts 1 km. >Then, after doing this it would be a piece of cake to come up with GPS >charts and whatnot using the 100 gr angle system. Current charts could >undergo very simple updates with just a footnote to it indicating what RL >is and all (except, of course, that these projections would refer to >decimal grids...). > >All airports in the world would use such RL as reference, and no longer the >SL. There would be no potential for confusion, the nautical mile trash >would be history (and so would the hideous knot...) and presto! > >I hope this answered your question, Pat. > >Marcus > > >Cheers, > > > >Pat Naughtin CAMS > >Geelong, Australia > > > >on 2002-08-17 01.18, Ma Be at [EMAIL PROTECTED] wrote: > > > >> Based on Joe's post below and other ones earlier shall we conclude that >we > >> still do not have the answer to the above question (in the subject)? > >> > >> Again, I launch the question what would prevent us from defining a >specific > >> diameter for purposes of navigation and cartography at some 560 m below >sea > >> level and use the principle of "relative" altitudes and all (like we >already > >> do with atmospheric pressure) to get rid of the nautical mile crap? > >> > >> Marcus > >> > >>>> J. F. Hayford reported to the International Geodetic and Geophysical >Union > >>>> in 1926 that; > >>>> Equatorial circumference of the earth = 40 076.594 km, > >>>> Polar circumference of the earth = 39 941.028 km. > >>>> My source does not state whether these figures are for sea level, as >seems > >>>> likely, or if they take account of land and mountains. However, the > >>>> uncertainty in the radius of the earth can not exceed 50 metres. >That is, > >>>> the uncertainty is only one part in 100 000. > >>>> > >>>> Joseph B.Reid... > >> > >> > >> Is your boss reading your email? ....Probably > >> Keep your messages private by using Lycos Mail. > >> Sign up today at http://mail.lycos.com > >> > > > > > > >Is your boss reading your email? ....Probably >Keep your messages private by using Lycos Mail. >Sign up today at http://mail.lycos.com _________________________________________________________________ Chat with friends online, try MSN Messenger: http://messenger.msn.com
