Re: [Re: [Re: calculating distance based on zip/postal codes]]

Jan Theodore Galkowski <jtgalkowski(at)alum.mit.edu> wrote:

> > No system is perfect, even stating a city doesn't help as from one en=
d =

> > to the other can easily be a 45 minute drive.

> Well, for this application, you might be able to use the arccosine rule=
=2E
> You just treat latitude and longitude as if they were rectangular =

> cartesian coordinates and calculate a distance:  If the result is =

> smaller than some threshold amount, you simply announce the people are =

> "close".  Otherwise you use the arccosine rules.  This idea will work =

> for any place having latitudes closer to the equator than the arctic or=
 =

> antarctic circles.

Three things:
#1: Define `close' (and `not far' doesn't count :-)
#2: Isn't there a page on the JPL website ( http://www.jpl.nasa.gov ) tha=
t
will calculate latitude and longitude based on your address?  This would
probably provide numbers close enough to work with.  (I didn't see anythi=
ng on
the MIT website; maybe you would know?)
#3: In your last mail, you said in part:
> Vector analysis is good for this. There are also more numerically stabl=
e =

> representations, such as quaternions (although, apart from religious =

> considerations, it's hard to make a case for them versus, say, spin =

> matrices, or rotation matrices themselves) or Rodrigues parameters (a =

> favorite of mine). =

> =

> In serious work, error analysis on the sphere is an important =

> consideration and, if the standard angular deviations are anything
> but tiny, involves some non-standard stuff which is the subject of =

> spherical statistics and spherical regression, eg, paleomagnetic =

> calculations.
Where can I go to get more info on this?

--Jedi Hacker(apprentice) and Code Poet

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