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Re: ??finding distance of E.Q. from given location??
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- Subject: Re: ??finding distance of E.Q. from given location??
- From: "Michael Valley" <mtv(--nospam--at)skilling.com>
- Date: Wed, 12 Jan 2000 13:37:07 -0700
- Comments: Authenticated sender is <mtv(--nospam--at)mail.skilling.com>
- Priority: normal
I use a program that I wrote for my calculator (based on pretty simple spherical-cartesian coordinate transformation). I assume a perfect sphere with R = 6366 km. Then I calculate the 3D cartesian coordinates of the two points. The chord distance between those points may be calculated as the SRSS of the component distances (X1-X2, etc.). Then I calculate the great circle distance based on the chord distance and radius of the earth. This method is in error in asmuchas the earth is not a perfect sphere. It looks like the web site you indicated can use other ellipsoid methods (which would be more accurate). Based on trials, the distance using a spherical assumption is in error by a small fraction of 1%, which is close enough for my purposes. Lat/lon information is reported on all earthquakes. Lat/lon information for a given address can be obtained by using www.mapblast.com. ********* > From: "Russel Madere" <rmadere(--nospam--at)bellsouth.net> > I use the Clark 1866 Geoid to calculate the coordinates of each location in > what ever unit I want and then use Algebra's Pythagerean Theorem to > calculate the distance. Not the quickest way by hand, but a PC can handle > the calculations in seconds. > ----- Original Message ----- > From: Khosrownia, Ghassem SPK <GKhosrownia(--nospam--at)spk.usace.army.mil> > > In trying to determine distance from epicenter of Hector-Mine and > Northridge > > earthquakes from some project sites I found the following link that can > help > > in converting the longitude latitude information to distances > > http://www.best.com/~williams/gccalc.htm. I have not looked at exactly how > > this is developed, but it seems the site is developed by a pilot for a > > pilot. Have you used something like this before? Would you know of a more > > reliable way to estimate the distances (except scaling off the maps)? - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Michael Valley, P.E., S.E. E-mail: mtv(--nospam--at)skilling.com Skilling Ward Magnusson Barkshire Inc. Tel:(206)292-1200 1301 Fifth Ave, #3200, Seattle WA 98101-2699 Fax: -1201
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