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Use this space to describe your geocache location, container, and how it's hidden to your reviewer. If you've made changes, tell the reviewer what changes you made. The more they know, the easier it is for them to publish your geocache. This note will not be visible to the public when your geocache is published.

Mystery Cache

Elliptical Reasoning

A cache by The Rat Send Message to Owner Message this owner
Hidden : 3/14/2004
4 out of 5
1 out of 5

Size: Size: micro (micro)

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How Geocaching Works

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Geocache Description:

The cache is not at the posted coordinates, but is less than a mile from those coordinates.

Given two points A and B, an ellipse is a set of all the points (C) such that the distance from Point C to Point A plus the distance from Point C to Point B is a fixed total. Points A and B are called the foci (pronounced FOE sigh - as in the Latin plural of focus). Two ellipses on the same plane can intersect at anywhere from 0 to 4 different points, as the above illustration shows.

To find the cache coordinates, you must identify the point(s) of intersection of two ellipses. These two ellipses have a common focus. The cache is located at a point such that it meets these two conditions:

The distance from Waypoint 1 to the cache plus the distance from Waypoint 2 to the cache is 5,000 meters.
The distance from Waypoint 2 to the cache plus the distance from Waypoint 3 to the cache is 10,000 meters.

Waypoint 1 is the location of my cache Circular Reasoning - the actual cache location, not the posted coordinates. Yes, that means you have to solve that puzzle before you can solve this one.

Waypoint 2: N37° 20.660 W122° 02.254

Waypoint 3: N37° 17.140 W122° 05.298

All distances were measured using Fizzymagic's FizzyCalc tool. This is a great little tool that all geocachers should have, even if you don't solve this puzzle. There is more than one solution to this puzzle. The correct solution does not require you to trespass on private property.

Additional Hints (Decrypt)


Decryption Key


(letter above equals below, and vice versa)



57 Logged Visits

Found it 47     Didn't find it 1     Write note 2     Temporarily Disable Listing 2     Enable Listing 2     Owner Maintenance 3     

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Current Time:
Last Updated: on 11/15/2017 3:57:56 PM (UTC-08:00) Pacific Time (US & Canada) (11:57 PM GMT)
Rendered From:Unknown
Coordinates are in the WGS84 datum

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