Hidden Treasure Game with GPS
 by 'Shorty' Routh  shorty@shortypen.com 

There is a game called Geocaching that is a treasure hunting sport where you use your GPS receiver to find caches hidden by others. The basic philosophy is that someone hides a container somewhere on public property, and then publishes the coordinates. When the cache hunters find the cache, they are expected to take a treasure, leave a new treasure, and write in the log book. As of this writing, there are over 14,000 caches hidden world wide, most of them in the United States. The majority of caches are hidden in parks and are meant for land lubbers, but there are caches that are only accessible by boat.


This is an inexpensive sport, all you need is a GPS receiver (mine cost $100). Everything else is free, just go to www.geocaching.com and create a login name. Anyone can hide caches, and anyone can hunt for them.  After a cache is found, the person can log on and record their finding with a note and even upload some pictures.


1 - Take a print out of the entire geocache log. Most hiders leave some sort of clue besides the coordinates, and the finders also give more clues when they register finding it. If you are out there and can’t find it, it really helps to have those notes with you.

2 - GPS receivers seem to have a “circle of confusion” when you get to the last 30 feet, in which they read sporadically, or zero out a distance from where the hider’s gps zeroed. A technique to overcome this is to stand off 50-100 feet away from where you think the cache is and read the direction the gps says the cache located. Then use a compass to sight where it is supposed to be. Then circle around to another spot and sight from there. This triangulation technique seems to help improve the accuracy and give a better idea where the cache is.

3 - If you are in a heavily wooded area, find a spot to take a reading with a clear shot of the sky. 

4 - There are plenty of poisonous snakes here in Texas so I use a walking stick to poke around in the underbrush.


1 - The biggest failure of geocache containers is that they leak and become water logged. Many people have been using Tupperware containers with the press on lids, and these just aren’t weather resistant enough to last. Some of the containers that do well are military ammo boxes and dry boxes meant for sportsmen that have a gasketed lid. I personally prefer to use a Rubbermaid #3142 Screw Top Jar. It is a clear plastic container with a waterproof lid that I have tested. I like the clear containers so that the person that finds the cache can look inside before opening it - wouldn’t want a surprise in there.

2 - Mother nature and careless cache hunters have a way of moving stuff out there, so another feature of my containers is that I bolt a loop to the lid, seal it with marine goop, and then tie the container to a tree root. I started doing this after one of my containers was lost in a flood, and another was lost because the lake water level was unusually low when I hid the cache, and it floated away when the water level returned.

3 - The GPS “circle of confusion” makes the last 30 feet a guessing game for the hunters, so I always place mine near a conspicuous landmark like a tree stump, or large rock. One cache I hunted for was in a grassy field. That cache was very difficult to find and took three trips because the grass was very tall and overgrew the whole area making the container especially hard to find. On the third trip I accidentally stepped on it, having previously just probed the area with my walking stick.


Traditional Cache - This is the typical type, a container which stores treasures and a log book.

Multi-Cache - This is a connect the dots type cache. After finding the first cache, you are given further coordinates of other caches which aren’t publicly listed.

Virtual Cache - This is just coordinates of an area, perhaps where they prohibit geocaching. Devils Tower is a good example, the original geocache there was removed by the park rangers.

Letterbox Hybrid - There is another game called letterboxing that uses clues instead of coordinates, and sometimes these are cross posted to both games.

Event Cache - These are events where the cache coordinates are published, for a get together.


A recent addition to the game is Travel Bugs. You can purchase dog tags from the Geocaching online store, and then attach them to a toy or other object. These are then placed in a cache for other cachers to pickup and move to another cache. Each travel bug has it's own page with a photo, description of their mission, and logs of who has picked it up and where it has gone.  http://www.geocaching.com/track/ - Tracking travel Bugs


There is one cache in Houston which is in plain sight along a sidewalk next to a bench. The cache is film canister very cleverly hidden in a log. You sit down at the bench, reach over and pickup the log, pop the end off and pull the canister out. Inside are a few small treasures and coins, along with a scroll of paper for a log.  -- Another clever one here in Houston is a film canister with a paper clip bent into a hook. The canister is then suspended inside the top of a pole which is a sign post.  http://www.geocaching.com/seek/cache_details.asp?ID=8904

Early in the game there was a cache where a guy bolted an ammo box to a tree, and locked it with a combination lock. The combination was published with the coordinates, so hunters could open the box when they visited it. This box was also in plain sight, and one day it was discovered the lock had been broken but replaced to look like it was locked. It was logged by someone who said they broke into it because they were curious, read the explanation note of what it was inside and was going to go get a GPS receiver later that day to start playing the game.

Hiding a cache on a beach is very difficult, the hider of “Pearl” in Louisiana solved this buy burying a steel rod with 6” above the sand.  After finding the rod the hunter goes 10 feet to magnetic north and then digs up the container. http://www.geocaching.com/seek/cache_details.asp?ID=1097 


www.geocaching.com  --- the main game site 
http://www.geocaching.com/track/  --- Tracking travel Bugs
alt.rec.geocaching --- usenet discussion group about geocaching
sci.geo.satellite-nav --- discussion of other gps topics
http://www.brillig.com/geocaching/maps.shtml  --- Buxley’s Maps of all
the geocaches
http://www.fcc.gov/mmb/asd/bickel/distance.html  -- Distance between 2
gps coordinates
http://www.gpsdrawing.com/gallery.htm  --- drawing the world with GPS
http://www.confluence.org/index.php  -- the Degree Confluence Project
http://joe.mehaffey.com/  --- tons of GPS info
http://www.shortypen.com/geo/  my personal geocaching page