calculating distance based on zip/postal codes]

Now that we've reviewed the scientific methods of calculating distances over
the surface of this sphere of us perhaps the original question is more
concerned with a simple approach for about $25 US.

DeLorme (www.delorme.com) has been selling an excellent CD-ROM (since about
1991) that we have used to do exactly what the original question stated. In
fact it does so much more. They market several versions (including one which
works with a small GPS received hooked up to the serial port of your
notebook) but the best (for the stated purpose) is probably the one they
make for AAA (sells for $25 US).

Our favorite is an older version (no longer sold but you can probably find
one via the World-Wide Web) labeled DeLorme Map Expert, Version 2.0 (for
Windows only). It was produced in 1993-4. It allows you to click on two or
more points and automatically sums the distances. It has been sufficiently
accurate for our uses (heck, the odometers of the modern computerized
automobile come up with many different totals for the same distance
traveled). We just hope we don't wear it out.

You can fone the company at 207-865-1234.  Their website may have a
toll-free number. Their e-mail address is: info(at)delorme.com.

(Wish I had stock in their company - we have certainly recommended their
stuff to enough people.

You want a SIMPLY, painless solution? Here it is.

Zzyvko Marjanovitch
webmaster(at)CarolinaNow.com et al




-----Original Message-----
From: owner-hwg-business(at)hwg.org [mailto:owner-hwg-business(at)hwg.org]On
Behalf Of Cathy Favre
Sent: Tuesday, May 16, 2000 03:03
To: Manewell, Brett; 'Jan Theodore Galkowski'
Cc: hwg-business
Subject: RE: [Re: calculating distance based on zip/postal codes]


I totally agree - I am impressed.

A great reason to keep tuning in...

regards,
Cathy Favre
IDON EAST Corporation
cfavre(at)idon.com

> -----Original Message-----
> From: owner-hwg-business(at)hwg.org [mailto:owner-hwg-business(at)hwg.org]On
> Behalf Of Manewell, Brett
> Sent: Monday, May 15, 2000 6:08 PM
> To: 'Jan Theodore Galkowski'
> Cc: hwg-business
> Subject: RE: [Re: calculating distance based on zip/postal codes]
>
>
> OK, I'm impressed already.
>
> I knew there was a good reason I subscr1bed to the hwg-business
> mail list ;)
>
> It's been 10 years since I did any heavy duty engineering maths at Uni and
> this is way beyond me getting my head around during my working
> day.  I think
> I'll just archive this discussion thread for later consideration.
>
> Thanks for the insight!
>
> regards
> Brett Manewell
> CSR Timber Products ISD
> BManewell(at)csr.com.au
>
>
> -----Original Message-----
> From: Jan Theodore Galkowski [mailto:jtgalkowski(at)alum.mit.edu]
> Sent: Tuesday, 16 May 2000 10:09
> Subject: Re: [Re: calculating distance based on zip/postal codes]
>
> >D= 6,370,997*arcos(sin(LAT1)*sin(LAT2) +
> cos(LAT1)*cos(LAT2)*cos(LONG1-LONG2))
> [snip]
>
> >Though I believe that this is the arc-cosine rule that Galkowski advised
> >against.
> Just to confirm Capt Ron's suspicion, yes, this is the problematic
> arccosine rule.  All's fine except that nasty cosine of the
> difference between two longitudes:  As the distance between the
> longitudes halves, you need more than double the amount of precision
> to get the same accuracy out of the expression.
>
> In general, folks who do a lot of 3-dimensional work on the sphere
> represent positions by unit vectors in 3-space and use their dot
> products as a reciprocal measure of distance between the points.
> To change that into a length, one can use a number of gimmicks
> which avoid having to push the quantity through a trig function.
> Indeed, most real-time 3-or-greater-space work avoids trig functions
> altogether, trying to reduce the calculation to +, -, *, /, and
> SQRT operations only.  Vector analysis is good for this.  There
> are also more numerically stable 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.
>   --jtg
> [snip]
>

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