International Geocaching Logo
|First played||May 3, 2000|
|Equipment||GPS receiver or GPS-enabled mobile device, writing utensil|
Geocaching is an outdoor sport in which the participants use a Global Positioning System (GPS) receiver or mobile device and other navigational techniques to hide and seek containers, called "geocaches" or "caches", anywhere in the world.
A typical cache is a small, waterproof container containing a logbook where the geocacher enters the date they found it and signs it with their established code name. Larger containers such as plastic storage containers (tupperware or similar) or ammunition boxes can also contain items for trading, usually toys or trinkets of little value. Geocaching is often described as a "game of high-tech hide and seek", sharing many aspects with benchmarking, trigpointing, orienteering, treasure-hunting, letterboxing, and waymarking.
Geocaches are currently placed in over 100 countries around the world and on all 7 continents, including Antarctica. After 10 years of activity there are over 1,532,000 active geocaches published on various websites. There are over 5 million geocachers worldwide.
Geocaching is similar to the 150-year-old game letterboxing, which uses clues and references to landmarks embedded in stories. Geocaching was conceived shortly after the removal of Selective Availability from GPS on May 2, 2000, because the improved accuracy of the system allowed for a small container to be specifically placed and located. The first documented placement of a GPS-located cache took place on May 3, 2000, by Dave Ulmer of Beavercreek, Oregon. The location was posted on the Usenet newsgroup as . By May 6, 2000, it had been found twice and logged once (by Mike Teague of Vancouver, Washington). According to Dave Ulmer's message, the original stash was a black plastic bucket buried most of the way in the ground and contained software, videos, books, food, money, and a slingshot.
The Oregon Public Broadcasting program Oregon Field Guide covered the topic of geocaching in a February 2010 episode, paying a visit to the original site. A memorial plaque now sits at the actual site, the Original Stash Tribute Plaque (GCGV0P).
Origin of the name
The activity was originally referred to as GPS stash hunt or gpsstashing. This was changed after a discussion in the gpsstash discussion group at eGroups (now Yahoo!). On May 30, 2000, Matt Stum suggested that "stash" could have negative connotations, and suggested instead "geocaching."
For the traditional geocache, a geocacher will place a waterproof container containing a log book (with pen or pencil) and trade items then record the cache's coordinates. These coordinates, along with other details of the location, are posted on a listing site (see list of some sites below). Other geocachers obtain the coordinates from that listing site and seek out the cache using their GPS handheld receivers. The finding geocachers record their exploits in the logbook and online. Geocachers are free to take objects (except the logbook, pencil, or stamp) from the cache in exchange for leaving something of similar or higher value.
Typical cache "treasures" are not high in monetary value but may hold personal value to the finder. Aside from the logbook, common cache contents are unusual coins or currency, small toys, ornamental buttons, CDs, or books. Also common are objects that are moved from cache to cache called "hitchhikers", such as Travel Bugs or Geocoins, whose travels may be logged and followed online. Cachers who initially place a Travel Bug or Geocoins often assign specific goals for their trackable items. Examples of goals are to be placed in a certain cache a long distance from home, or to travel to a certain country, or to travel faster and farther than other hitchhikers in a race. Higher value items are occasionally included in geocaches as a reward for the First to Find (called "FTF"), or in locations which are harder to reach. Dangerous or illegal items, weapons, and pornography are generally not allowed and are specifically against the rules of most geocache listing sites.
Geocache container sizes range from "nanos", which can be smaller than the tip of finger and only have enough room to store the log sheet, to 20 liter (5 gallon) buckets or even larger containers. The most common cache containers in rural areas are lunch-box sized plastic storage containers or surplus military ammunition cans. Ammo cans are considered the gold standard of containers because they are very sturdy, waterproof, animal and fire resistant, relatively cheap, and have plenty of room for trade items. Smaller containers are more common in urban areas because they can be more easily hidden.
If a geocache has been vandalized or stolen it is said to have been "muggled" or "plundered." The former term plays off the fact that those not familiar with geocaching are called muggles, a term borrowed from the Harry Potter series of books which was rising in popularity at the same time Geocaching got its start.
Geocaches vary in size, difficulty, and location. Simple caches are often called "drive-bys," "park 'n grabs" (PNGs), or "cache and dash." Geocaches may also be complex, involving lengthy searches or significant travel. Examples include staged multi-caches; underwater caches, caches located 50 feet (15 m) up a tree, caches found only after long offroad drives, caches on high mountain peaks, caches located in challenging environments (such as Antarctica  or north of the Arctic Circle), and magnetic caches attached to metal structures and/or objects. Different geocaching websites list different variations per their own policies (e.g. Geocaching.com does not list new Webcam, Virtual, Locationless, or Moving geocaches). The traditional Geocaching gave birth to GeoCaching – one of active urban games of Encounter project. The game is quite similar to Geocaching but has time limitations and hints in it.
Variations of geocaches (as listed on geocaching.com) include:
- Traditional: The basic cache type, a traditional cache must include a log book of some sort. It may or may not include trade or traceable items. A traditional cache is distinguished from other cache variations in that the geocache is found at the coordinates given and involves only one stage.
- Multi-cache: This variation consists of multiple discoveries of one or more intermediate points containing the coordinates for the next stage; the final stage contains the log book and trade items.
- Offset: This cache is similar to the multi-cache except that the initial coordinates are for a location containing information that encodes the final cache coordinates. An example would be to direct the finder to a plaque where the digits of a date on the plaque correspond to coordinates of the final cache.
- Mystery/puzzle: This cache requires one to discover information or solve a puzzle to find the cache. Some mystery caches provide a false set of coordinates with a puzzle that must be solved to determine the final cache location. In other cases, the given location is accurate, but the name of the location or other features are themselves a puzzle leading to the final cache. Alternatively, additional information is necessary to complete the find, such as a padlock combination to access the cache.
- Night Cache: These multi-stage caches are designed to be found at night and generally involve following a series of reflectors with a flashlight to the final cache location.
- Letterbox Hybrid: A letterbox hybrid cache is a combination of a geocache and a letterbox in the same container. A letterbox has a rubber stamp and a logbook instead of tradable items. Letterboxers carry their own stamp with them, to stamp the letterbox's log book and inversely stamp their personal log book with the letterbox stamp. The hybrid cache contains the important materials for this and may or may not include trade items. Whether the letterbox hybrid contains trade items is up to the owner.
- Locationless/Reverse: This variation is similar to a scavenger hunt. A description is given for something to find, such as a one-room schoolhouse, and the finder locates an example of this object. The finder records the location using their GPS hand-held receiver and often takes a picture at the location showing the named object and his or her GPS receiver. Typically others are not allowed to log that same location as a find.
- Moving/Travelling: Similar to a traditional geocache, this variation is found at a listed set of coordinates. The finder uses the log book, trades trinkets, and then hides the cache in a different location. By updating this new location on the listing, the finder essentially becomes the hider, and the next finder continues the cycle. The hitchhiker concept (see above) has superseded this cache type on geocaching.com.
- Virtual: Caches of this nature are coordinates for a location that does not contain the traditional box, log book, or trade items. Instead, the location contains some other described object. Validation for finding a virtual cache generally requires you to email the cache hider with information such as a date or a name on a plaque, or to post a picture of yourself at the site with GPS receiver in hand.
- Earthcache: A type of virtual-cache which is maintained by the Geological Society of America. The cacher usually has to perform a task which teaches him/her an educational lesson about the earth science of the cache area.
- Webcam: Similar to a virtual cache; there is no container, log book, or trade items for this cache type. Instead, the coordinates are for a location with a public webcam. Instead of signing a log book, the finder is often required to capture their image from the webcam for verification of the find.
- Event Cache: This is a gathering organized and attended by geocachers. Physical caches placed at events are often active only for the event date.
- Cache-In Trash-Out (CITO) Events: This variation on event caching is a coordinated activity of trash pickup and other maintenance to improve the environment.
- Mega Event: An event that is attended by over 500 people. Mega Events are typically annual events, usually attracting geocachers from all over the world.
- GPS Adventures Maze Exhibit: An exhibit at various museums and science centers in which participants in the maze learn about geocaching. These "events" have their own cache type on Geocaching.com and include many non-geocachers.
- Wherigo cache: A Wherigo cache is similar to a multi-stage cache hunt that uses a Wherigo cartridge to guide the player. The player plays the cartridge and finds a physical cache sometime during cartridge play, usually at the end. Not all Wherigo cartridges incorporate geocaches into game play. Wherigo caches are unique to the geocaching.com website.
- BIT Cache(tm): Physical yet containerless caches, they are laminated cards with a URL and the password needed for logging. More information is available at www.BITcaching.com. They are listed exclusively on Opencaching.us - 
- Guest Book Cache: Physical guest books often found in museums, tourist information centers, etc. They are listed exclusively at Opencaching.us - 
- USB Cache: Paperless caches stored inside USB drives and embedded (with permission) into walls or other structures. The cache is retrieved by connecting a device that has a USB port and that is able to read standard text files. Also known as Dead Drop caches. 
GPX files contain information such as a cache description and information about recent visitors to the cache. Geocachers may upload geocache data (also known as waypoints) from various websites in various formats, most commonly in file-type GPX, which uses XML. Some websites allow geocachers to search (build queries) for multiple caches within a geographic area based on criteria such as Zip Code or coordinates, downloading the results as an email attachment on a schedule. In the recent years, Android and iPhone users have been able to download apps such as GeoBeagle that allow them to use their 3G/Gps enabled devices to actively search for and download new caches.
Converting and filtering data
A variety of geocaching applications are available for geocache data management, file-type translation, and personalization. Geocaching software can assign special icons or search (filter) for caches based on certain criteria (e.g. distance from an assigned point, difficulty, date last found).
Paperless geocaching means hunting a geocache without a physical printout of the cache description. Traditionally, this means that the seeker has an electronic means of viewing the cache information in the field, such as pre-downloading the information to a PDA or other electronic device. Various applications are able to directly upload and read GPX files without further conversion. Newer GPS devices released by Garmin, DeLorme and Magellan have the ability to read GPX files directly, thus eliminating the need for a PDA. Other methods include viewing real-time information on a portable computer with internet access or with a web-enabled smart phone. The latest advancement of this practice involves installing dedicated applications on a smart phone with a built-in GPS receiver. Seekers can search for and download caches in their immediate vicinity directly to the application and use the on-board GPS receiver to find the cache.
A more controversial version of paperless caching involves mass-downloading only the coordinates and cache names (or waypoint IDs) for hundreds of caches into older receivers. This is a common practice of some cachers and has been used successfully for years. In many cases, however, the cache description and hint are never read by the seeker before hunting the cache. This means they are unaware of potential restrictions such as limited hunt times, park open/close times, off-limit areas, and suggested parking locations.
The website geocaching.com now sells mobile applications which allow users to view caches through a variety of different devices. Currently, the Android, iPhone, webOS, and Windows Phone 7 mobile platforms have applications in their respective stores. The app also allows for a trial version with limited functionality. Additionally "c:geo - opensource" is a free opensource full function application for Android phones that is very popular.
In mid-2010, Groundspeak added the souvenir feature to the website. By finding certain caches or finding caches on a certain date, a geocacher earns a special icon which is posted on that cacher's profile page.
Geodashing is an outdoor sport in which teams of players use GPS receivers to find and visit randomly-selected "dashpoints" (also called "waypoints") around the world and report what they find. The objective is to visit as many dashpoints as possible.
The first game organized by gpsgames.org ran for two months (June and July 2001); each subsequent game has run for one month. Players are often encouraged to take pictures at the dashpoints and upload them to the site.
There are various acronyms and words commonly used when discussing geocaching.
- Cache – A box or container that contains, at the very least, a logbook.
- Geoswag – The items that can be found in some larger caches.
- Muggle – A non-geocacher.
- Muggled - Being caught by a non-geocacher while retrieving/replacing a cache; also, a muggled cache has been removed or vandalized by a non-geocacher, usually out of misunderstanding or lack of knowledge.
- Smiley – A cache find. Refers to the "smiley-face" icon attached to "Found It" logs on some listing sites.
- BYOP – (Bring Your Own Pen/Pencil) The cache in question lacks a writing device for the logbook.
- CITO – (Cache In Trash Out) and refers to picking up trash on the hunt.
- CO – (Cache Owner) The person who is responsible for maintaining a cache, usually the person who hid it.
- DNF – (Did Not Find) Did not find the cache container being searched for.
- FIGS - Found in good shape.
- FTF – (First To Find) The first person to find a cache container.
- FTL – (First To Log) The first person to log the find of a cache container online.
- GPS – Short for Global Positioning System, also occasionally refers to the receiver itself.
- GPSr – Short for GPS receiver.
- PAF - Phone-A-Friend.
- SGC - (Senior Geocacher) An experienced participant of the pursuit.
Logging a hunt:
- TFTC – (Thanks For The Cache) This is often used at the end of logs to thank the cache owner.
- TFTH – (Thanks For The Hunt or Hide or Hike) It shares the same purpose as TFTC, but can also be used when the cache was not found.
- TN – (Took Nothing) no trade or traveling item was removed from the cache.
- LN – (Left Nothing) no trade or traveling item was added to the cache.
- XN – (eXchanged Nothing) combines the previous two acronyms; nothing was removed or added.
- SL – (Signed Log) used when the participant visited the cache and signed its logbook.
- TSIA – (The Streak is Alive) used when the participant has an active streak of continous days finding a cache.
Note: the various acronyms in this section are often combined in various ways, such as "TNLNSL, TFTC!"
Location description or hint:
- GRC – (GuardRail Cache) used in the description on where a cache may be hidden.
- GZ – (Ground Zero or Geo-zone) refers to the general area in which a cache is hidden.
- ICT – (Ivy Covered Tree) used in the description on where a cache may be hidden.
- LPC – (Light/Lamp Post Cache) used in the description on where a cache may be hidden.
- MKH – (Magnetic Key Holder) used in the description on the type of container used for the cache.
- PLC – (Parking Lot Cache) used in the description on where a cache may be hidden.
- POR – (Pile Of Rocks) used in the description on where a cache may be hidden.
- POS – (Pile Of Sticks or Stones) used in the description on where a cache may be hidden.
- SL - (Skirt Lifter) refers to the metal or plastic skirt at the base of a lightpole.
- UFO – (Unnatural Formation of Objects) a pile of material that obviously did not form naturally and is a likely cache hiding spot.
- UPS – (Unnatural Pile of Sticks) a piles of sticks that did not form naturally and where a cache may be hidden.
On 10 October 2010 geocachers around the world held events and went caching to commemorate 10 years of geocaching. In the process they broke the record for the most geocachers to find a cache in a day, with 78,313 accounts logging a cache.
Individual geocaching websites have developed their own guidelines for acceptable geocache publications. Though not universally required, the Geocacher's Creed provides ethical search guidelines. Government agencies and others responsible for public use of land often publish guidelines for geocaching. Generally accepted rules are to not endanger others, to minimize the impact on nature, to respect private property, and to avoid public alarm.
Controversy and issues
Cachers have been approached by police and questioned when they were seen as acting suspiciously. Other times, investigation of a cache location after suspicious activity was reported has resulted in police and bomb squad discovery of the geocache. Schools have been occasionally evacuated when a cache has been seen by teachers or police, as in the case of Fairview High School in 2009. A number of caches have been destroyed by bomb squads.
The placement of geocaches has critics among some government personnel and the public at large who consider it littering. Some geocachers try to mitigate this perception by picking up litter while they search for geocaches. Geocaching is not illegal in the United States and is usually positively received when explained to law enforcement officials. However, certain types of placements can be problematic. Although disallowed, hiders could place caches on private property without adequate permission (intentionally or otherwise), which encourages cache finders to trespass. Caches might also be hidden in places where the act of searching can make a finder look suspicious (e.g. near schools, children's playgrounds, banks, courthouses, or in residential neighborhoods), or where the container placement could be mistaken for a drug stash or a bomb (especially in urban settings, under bridges, near banks, courthouses, or embassies). As well as concerns about littering and bomb threats, some geocachers hide their caches in inappropriate locations, that may encourage risky behaviour, especially amongst children. Examples include electrical boxes and light pole covers. Hides in these areas are discouraged, and cache listing websites enforce guidelines that disallow certain types of placements. However, as cache reviewers typically cannot see exactly where and how every particular cache is hidden, problematic hides can slip through. Ultimately it is also up to cache finders to use discretion when attempting to search for a cache, and report any problems.
The South Carolina House of Representatives passed Bill 3777 in 2005, stating, "It is unlawful for a person to engage in the activity of geocaching or letterboxing in a cemetery or in an historic or archeological site or property publicly identified by an historical marker without the express written consent of the owner or entity which oversees that cemetery site or property." The bill was referred to committee on first reading in the Senate and has been there ever since.
Websites and Data Ownership
Numerous websites list geocaches around the world. In the United States, where most geocaching services are hosted, only a cache's coordinates are in public domain. Other cache information, including the description, is protected by copyright law. Geocaching websites vary in active protection of cache data.
The first website to list geocaches was announced by Mike Teague on May 8, 2000. On September 2, 2000, Jeremy Irish emailed the gpsstash mailing list that he had registered the domain name geocaching.com and had set up his own Web site. He copied the caches from Mike Teague's database into his own. On September 7, Mike Teague announced that Jeremy Irish was taking over cache listings.
The largest site is Geocaching.com, owned by Groundspeak Inc., which began operating on September 2, 2000. With a worldwide membership the website lists over 1.5 million caches. Each cache is reviewed by regional cache reviewers before publication. Free basic membership allows users to see coordinates for most caches in its database; premium membership includes a fee for additional features, including advanced search tools and caches designed for premium members. The website includes 1,581,628 caches in over 200 countries around the world, as of November, 2011.
The website no longer lists new caches without a physical container, including virtual and webcam caches; however, older caches of these types have been grandfathered in (except for locationless/reverse, which are completely archived). Earthcaches are the exception to the no-container rule; they are caches in which players must answer geological questions to complete the cache. Groundspeak created a waymarking website to handle all other non-physical caches.
The website also supports the discovery of benchmarks in the USA. There are currently no benchmarks outside the USA in their database. The website provides the best known longitude and latitude (sometimes only accurate to within six or more seconds) of the object along with a description. Hunters use the clues to try to find the benchmark; the benchmark can be logged as Found, Not Found, Note, or Destroyed. The "Destroyed" log should only be used if there is evidence that the mark has been permanently destroyed.
Groundspeak allows extraterrestrial caches, e.g. the Moon or Mars, although the website only presently provides earthbound coordinates. Thus the cache that exists on the International Space Station, GC1BE91, uses the Russian launch area as its position.
Geocaching.com has been criticized for its uncooperative stance towards mobile application developers, and for continuously delaying the release of a promised open API.  Some progress has been made recently, with the site now promoting mobile applications branded as Geocaching Live Enabled, and listing 7 applications (both mobile and browser/desktop based) that are using their soon to be released public API. 
Navicache.com started as a regional listing service around February 2001, but quickly gained popularity among those looking for a less restrictive alternative to what was currently available. While many of the websites listings have been posted to other sites, they also offer many unique listings. The website lists nearly any type of geocache (within reason) and does not charge to access any of the caches listed in their database. While all submissions are reviewed and approved, Navicache is more liberal in approving caches believing that the pastime belongs to participants rather than a governing agency.
The Opencaching Network provides independent, non-commercial listing sites based in the cacher's country or region. The Opencaching Network lists the most types of caches, including traditional, virtual, moving, multi, quiz, webcam, BIT, guest book, USB, event and MP3. The Opencaching Network is less restrictive than many sites, and does not charge for the use of the sites. All listings are reviewed by the network operators before being published and although cross-listing is permitted, it is discouraged. Some listings are listed on other sites, but there are many that are unique to the Opencaching Network. Features include the ability to organize your favorite caches, build custom searches, be instantly notified of new caches in your area, seek and create caches of all types, export GPX queries, statpics, etc. Each Opencaching Node provides the same API for free (called "OKAPI") for developers who want to create third-party application with Opencaching Network's content.
Terracaching seeks to provide high-quality caches made so by the difficulty of the hide or from the quality of the location. Membership is managed through a sponsorship system, and each cache is under continual peer review from other members. Terracaching.com embraces virtual caches alongside traditional/multi-stage caches and includes many locationless caches among the thousands of caches in its database. It is increasingly attracting members who like the point system. In Europe TerraCaching is supported by Terracaching.eu. This site is translated in different European languages, has an extended FAQ and extra supporting tools for TerraCaching.
Terracaching does not allow caches that are listed on other sites, so called double-listing.
GPSgames is a more open geocaching website that allows the geocaching community more flexibility in the types of geocaches placed. The traditional geocaches are more common, but, virtual, locationless, and traveler geocaches are still allowed. Other GPS games are also available. Geodashing, Shutterspot, GeoVexilla, MinuteWar, GeoPoker, and GeoGolf are among the other GPS games available.
Not to be mistaken for opencaching.us, opencaching.com aims to be as free and open as possible with no paid content. Caches are approved by a community process and coordinates are available without an account. Traditional, puzzle, virtual, and multi caches are supported. All caches published on opencaching.com are available under an Open Source license. The site was created by Garmin, but owning a Garmin device is not required for the full use of the site, as there are several Android and iPhone apps that lets users access the site while on the trail.
Opencaching.com also provides a free API for developers that want to utilize the site's content.
Opencaching.com does allow caches that are listed on other sites, so called double-listing.
In many countries there are regional geocaching sites, but these mostly only compile lists of caches in the area from the three main sites. Many of them also accept unique listings of caches for their site, but these listings tend to be less popular than the international sites, although occasionally the regional sites may have more caches than the international sites. There are some exceptions though, e.g. in the former Soviet Union the site Geocaching.su remains popular because it accepts listings in the Cyrillic script. Additional international sites include Geocaching.de, a German website, and Geocaching Australia, which accepts listings of cache types depreciated by geocaching.com as well as traditional geocaches.
- Benchmarking (geolocating)
- Dead drop
- Degree Confluence Project
- Encounter (game)
- Location-based game
- Minnesota State Park Geocaching Challenge
- Transmitter hunting
- The Joy of Geocaching by Paul and Dana Gillin (ISBN 1-88495-699-8)
- The Essential Guide to Geocaching by Mike Dyer (ISBN 1-55591-522-1)
- The Complete Idiot's Guide to Geocaching by Jack W. Peters (ISBN 1-59257-235-9)
- Geocaching For Dummies by Joel McNamara (ISBN 978-0-7645-7571-6)
- Geocaching: Hike and Seek with Your GPS by Erik Sherman (ISBN 978-1590591222)
- The Geocaching Handbook (Falcon Guide) by Layne Cameron and Dave Ulmer (ISBN 978-076273044)
- Let's Go Geocaching by DK Publishing (ISBN 978-0-7566-3717-0)
- It's a Treasure Hunt! Geocaching & Letterboxing by Cq Products (ISBN 978-1563832680)
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- "GPS Reviews".
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- Deadly Caching
- 2005–2006 Bill 3777: Geocache, geocaching, and letterboxing South Carolina Legislature Online
- Haynie, Rachel (May 20, 2005). "High–tech scavenger hunt Geocachers invade hallowed ground". Columbia Star. Retrieved 3 March 2010.
- Benchmark Hunting
- Opencaching Network API
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