# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: Interesting challenge
From: Lu Abel
Date: 2012 Aug 5, 19:06 -0700
Right, but is there a closed-form solution?   I know, for example, that that's the way GPS works (by distance from the instantaneous position of the satellites), but I believe that GPS finds it easier to use an iterative methodology (assume a position, see if the data fit, if not adjust the assumed position, iterate).

For those curious about how I got started on this:   A friend of mine who is a super expert on computers runs the web sites for several startup companies, with Internet access provided by Comcast (the cable TV provider here in northern California).   These machines are located in his home in San Jose.  He found some Comcast "support" feature that gave the position of his servers based on their IP address -- it said Orem, Utah!  It then offered to calculate the distance from the server to major cities in the US -- and came up with 6003 miles to San Jose, 5557 miles to Portland, Oregon, and 5420 miles to Houston, etc.   My friend looked at the numbers, played around with them, and somehow tried Nice, France as a location.  Comes out very well.

One major problem in trying to find Lat/Long even using Nice as a Assumed Position is that the starting direction for great-circle to San Jose is 322 deg, while the starting direction to Houston is 300 deg.   Not a very good crossing angle!

For you computer experts, NO, the reason for these weird distances is not that router delays were being included in the distances.  Or at least Comcast was claiming that the distance was measured by some other method than ping times.

From: Dave Walden <waldendand@yahoo.com>
To: NavList@fer3.com
Sent: Sunday, August 5, 2012 3:46 PM
Subject: [NavList] Re: Interesting challenge

doing each pair will give two possibilities. do all pairs, and one point should be in common.
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