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Bearnings Need Grease


RPaske

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I have been working on the following cache: http://www.geocaching.com/seek/cache_details.aspx?ID=41136 . I have a Garmin map76. In this cache I have three objects with three different bearings. Where the three bearning lines meet is where the the cache will be found. Question 1: How can I use the coordinates of these three objects to find the point of intersection? Question 2: If possible, how can I use my gps to accomplish the triangulation?

 

[This message was edited by RPaske on October 30, 2002 at 04:24 PM.]

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I have a GPS 76 and have done a cache that was similar to this one. My recommendation is to enter a waypoint for each of the given positions, then go to the map page, press menu and select "Measure Distance". Move the pointer to one of the waypoints, press enter to make that the measuring point, then use the cursor to move out on the correct bearing and place some waypoints on that bearing in the approximate area where you suspect the triangulation to converge, so you can see the bearing line from that point. Do the same thing two more times and look where the bearing lines converge, set a waypoint in the center and that should be the cache position.

 

You will probably need to "play" a bit with the measure distance function to learn how it works, but I have found this to be an excellent feature of the GPS76. It also works well for projecting waypoints or for finding a position given bearing and distance.

 

OH yeah, make sure you have the GPS set correctly for either true or magnetic bearings, as applicable.

 

FWIW,

CharlieP

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My mistake. Thought you were hiding the cache, not searching for it. So let's try again.

 

1) Set your GPS to diplay coordinates in UTM format.

 

2) Mark a piece of graph paper with a UTM grid appropriate to the coordinates of the three points.

 

3) Use a protractor to draw the bearing lines from each point.

 

4) The intersection points of the lines will form a triangle. With luck it will be quite small.

 

5) Read off the coordinates of the center of the little triangle formed by the three bearing lines.

 

6) Search at the point indicated by the coordinates

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