Hide and seek

The search for hidden treasure is usually associated with fantasy, Old World explorers hunting cities of gold, and pirates finding buried gold.

The phenomenon called geocaching brings the thrill of discovery into the 21st century.

The word geocaching (pronounced jee-oh-cash-ing) is constructed of geo for geography, and caching for the process of hiding a cache. A cache is used in hiking and camping as a hiding place for concealing and preserving provisions.

Geocaching is a sort of a scavenger hunt for GPS users. Participating in a geocache hunt is a good way to take advantage of the capability of a GPS unit.

The basic idea is to have individuals and organizations establish caches throughout the world and share the coordinates of these caches on the Internet. GPS users can then use the location coordinates to find the caches.

"I have been caching for almost six years and have found caches in all 50 states," said a geocacher from Starkville, Miss. who goes by DavidMac. "I've also completed the Alabama County Challenge to find a cache in each county in the state."

Once found, a cache may provide the visitor with a wide variety of rewards. The visitor is asked to leave something in place of the treasure he or she took.

The game is deceptively easy. One person hides a cache, then records its latitude and longitude coordinates with his GPS unit. He would then go to the Internet, to a site such as geocaching.com, and post a coordinates of the item.

Trying to find the cache means tracking the general location of the coordinates, and then figuring out where it's actually placed. The caches may be hidden under rocks, in trees - anywhere in the area. They, however, are never buried.

Most GPS units can condense the search area to about 20 feet, depending on the signal strength.

Geocaching is a relatively new phenomenon, and the rules are very simple: take something from the cache, leave something in the cache and write about it in the logbook.

A cache can come in many forms, but the first item should always be the logbook. The logbook contains information from the founder of the cache and notes from the cache's visitors.

The logbook can contain much valuable notes, such as information about nearby attractions, coordinates to other unpublished caches and even jokes written by visitors.

Larger caches may consist of a waterproof plastic bucket placed tastefully within the local terrain. The container will hold the logbook and any number of more or less valuable items. These items turn the cache into a true treasure hunt. You never know what the founder or other visitors of the cache may have left there for you to enjoy.

"The most interesting item I found in a cache is a travel bug medallion from Portugal," said Joe Copeland, who goes by Blugras.

"It honored the Portuguese explorer Bartolomeu Dias. He was the first known European to sail around the Cape of Good Hope since ancient times."

A travel bug is a small tag with a tracking number so those who find it can log on the Internet where it was found.

Travel bugs are not meant to be kept, and many have specific goals on where they want to go, just on the cacher's willingness and ability to travel.

Items in a bucket cache could be: Maps, books, software, hardware, CDs, videos, pictures, money, jewelry, tickets, antiques, tools, games, etc.

Geocaching is a family sport, so dangerous items such as explosives, knives, alcohol and anything illegal or inappropriate for children are not allowed.

It is recommended that items in a bucket cache be individually packaged in a clear zipped plastic bag to protect them.

According to geocaching.com, there are more than 150 geocaches in the Shoals. An hour and a GPS unit are the only things needed to find five caches in McFarland Park in Florence, though a sense of curiosity and adventure help, too.

As a general rule, caches are placed in areas of interest. Geocachers can discover beautiful overlooks, relaxing hikes and fun swimming holes that they never knew existed.

Some caches are at places of historical interest, so it can be educational, too. In that sense, you really discover a two-fold treasure: the cache itself and the area surrounding it.

"One find that will never leave our memories was placed near a waterfall just outside Cullman," said Copeland. "The waterfall was much larger than we expected, and we would not have known about it otherwise."

A recent offshoot of geocaching is geohashing.

Geohashing is a "spontaneous adventure generator," and was created by Randall Munroe, artist of the webcomic xkcd.

Found at xkcd.com, the letters don't actually mean anything. Munroe chose the word with no phonetic pronunciation to make the comic stand out.

The comic published

May 21 contained an algorithm to convert a given day's Dow Jones industrial average opening into a set of

coordinates.

The coordinates are then placed in a graticule, a box made from the nearest latitude and longitude lines. Each graticule gets the same random coordinate, which changes daily.

The Florence graticule is at latitude 34, longitude 87, about 55 miles wide and 70 miles tall.

Rather than being location to find a cache, geohashes are designed for meetings. The Web site proclaims that official meet-ups are Saturdays at 4 p.m.

A hash is the name for the algorithm type, which takes a line of data and encrypts it into hexidecimal format. In this case, the data is a string of numbers; a date, and that date's Dow number.

Encryting that string using an Md5 hash turns it into a string of 32 hex characters.

Translate the hex into decimals, and plug them into the graticule, and the location is pinpointed.

Readers may find the online daily generator easier: http://irc.peeron.com/xkcd/map/