NavList:

Charles V., you wrote:
"The method used depends on the number of observations: the intersection of 2 LOPs when only two sights were made, the symmedian center of the triangle formed by 3 LOPs, or the centroid of all the intersections of 4 or more LOPs."

The solution should not depend on the number of observations. I have the sense that you may not have discovered the computation section in the back of the modern Nautical Almanac. It's worth exploring. Most of it you already know, but there are a few extra bits... The code there covers all cases. By the way, is a "centroid" a truly valid fix? A "close enough" fix? Maybe harmlessly inaccurate in many practical cases, but there's no reason to stick with a wrong solution.

Also, just as a matter of reaching your "market" (and I use that broadly --if you're not trying to sell your product, you have a market), the word "symmedian" is a kiss-of-death. You're calculating the fix. It doesn't need to be named with a geometer's term. Maybe as an alternative, if you want it to sound more formal, you could just call it a "least squares fix" which will sound familiar to far more people than the obscure term "symmedian".

Can your code be adapted to other programmable calculators? Before your original description, I had never even heard of this particular HP calculator. If it were cheap, I might even have considered it for navigation. If you hope to reach more people with your creation, you may want to explore options for other devices.

Frank Reed