How Geocaching Works

By: Jonathan Strickland
Hidden geocaching box Ra-photos / Getty Images

Have you ever daydreamed about going on a hunt for a hidden treasure? Today, thousands of people around the world are doing just that through geocaching. Geocachers seek out treasures hidden by other players while exploring interesting locations.

At its most basic level, geocaching is a game where players use GPS receivers to track down a container, or cache. Caches may contain any number of small items, or they may only contain a logbook for players to sign to mark their find.


To understand what geocaching is all about, let's take a look at its history. In the spring of 2000, the U.S. government discontinued Selective Availability, its practice of degrading publicly-available GPS signals. Under this initiative, the GPS inserted random errors in signals for commercial receivers that made accurately determining your position impossible -- your reading could be off by as much as 300 feet. The purpose for the program was to give the U.S. military an advantage with GPS hardware. However, the military developed technology that would allow them to scramble GPS signals over sensitive areas, so Selective Availability became obsolete. Once it was switched off, it became possible for someone with a commercial GPS receiver to determine his own location with much greater accuracy. These days, you can usually determine your position within a range of 6 to 20 feet. The increase in accuracy is what makes geocaching feasible.

In the next section, we'll look at the people responsible for starting the geocaching craze.


Geocaching Pioneers

Artist's concept of the GPS satellite constellation
Image courtesy U.S. Department of Defense

Like many technologies, GPS receivers inspired a community of enthusiasts and early adopters. GPS receiver owners were excited that they would have access to much more accurate data much earlier than expected (the government had originally planned to turn off Selective Availability in 2006). One of these enthusiasts, Dave Ulmer, thought it might be fun to test GPS receiver accuracy by hiding a container in a remote area in Oregon and then posting the container's coordinates on a GPS user group on the Web. He put a logbook, a pencil and several small prizes in the container. His post included the instruction, "Take some stuff, leave some stuff."

It took only three days before two GPS enthusiasts found the container (independently of one another) and reported back to the user group. The container was left in the same position so that other people could find it and log their experience. Many GPS receiver users wanted to play, but they lived too far away to hunt for Dave's container. Enterprising users began to create their own caches. Mike Teague, who was the first to find David's container, began to post cache coordinates on his own Web site. At first, the game was called "GPS Stash Hunt," though it didn't take long before other players suggested alternative names. Matt Stum suggested geocaching, combining the words geo, meaning Earth, and cache, meaning a temporary storage location. The name gained wide acceptance and is the most popular term used to describe the game today.


It is interesting to note that Dave Ulmer's exercise set the standard for almost all future caches. While it's true that a cache doesn't have to include anything more than a logbook (and virtual caches don't even need that much -- more on that later), most caches are remarkably similar to the first one. More often than not, they include a logbook and several small prizes that players can take as long as they contribute new prizes to the cache.

In the next section, we'll look at what it takes to go on a geocache hunt.


Geocache Basic Equipment

Thales MobileMapper Pro GPS Package
Image courtesy Consumer Guide Products

To find a cache, you'll first need the correct coordinates. There are many Web sites with searchable geocache databases, like Some sites require you to create an account before you can access their information, but the process is usually free for basic membership. You'll probably want to look for a cache that is pretty close to where you live. Most sites provide a rating telling you how difficult the terrain is or how hard it will be to find the cache once you're in the right location. If the cache entry has comments from other players, you'll probably want to read those as well.

Now that you have the coordinates for your first cache hunt, it's time to gear up. The most important piece of equipment for nearly all geocache hunts is a GPS receiver. Without the receiver, you're going to have a hard time figuring out which way to go or how close you are to the cache. Receivers, at the very least, provide you with a direction and a distance to the coordinates you program into the device (called a waypoint).


Before you make a trip out to an unfamiliar place to hunt for a cache, it's very important that you learn how to use your new GPS receiver. Not all receivers are alike. You'll also want to check your receiver's accuracy. One way to do this is to pick a marked location and check your coordinates using the receiver. Then, leave the area and program the location's coordinates into your device, using it to guide you back to the site. This way you can see how close the receiver will help you get to a set of coordinates, giving you an idea of how large a search area you'll need to deal with when on a hunt.

Another vital item is a good topographical map of the cache's general location. A GPS receiver is great, but it won't tell you if there's a river or chasm between you and your destination (unless you purchase a receiver that can store maps, of course). To avoid nasty surprises, it's important that you have a good idea of what you're heading into before it's too late. Few things are more frustrating for a geocacher than the discovery of an impassible obstacle between him and his goal. It's also important to determine if your map used NAD27 or WSG84 to calculate coordinates -- you want to make sure that the coordinates in your receiver and the ones on the map refer to the same location.

In the next section, we’ll look at some optional equipment you may want to bring along on a hunt.


Additional Geocaching Equipment

Navigate with map and compass to travel direction.

If your GPS receiver doesn't have a compass feature, it's a good idea to bring one with you. They can be handy when you need to find your way back once you've found your cache -- or once you've given up. One handy tip for retracing your steps is to program your starting location as a waypoint in your receiver. Sometimes, though, you may have to find an alternative route back if the path you took is too difficult to retrace.

Because players can hide caches in clever -- and challenging -- locations, you'll want to make sure you have the appropriate gear with you. You might need a snorkel mask or even SCUBA gear if the cache is underwater, or you may need rock climbing equipment if it's placed on the side of a cliff. In general, most geocachers recommend the following standard gear for any cache located in the wilderness:


  • A buddy
  • Water
  • Sunblock
  • Hiking shoes
  • Bug repellent
  • First Aid kit/snake bite kit
  • Extra batteries for the receiver
  • Flashlight

Of course, some caches might be in city environments. In that case, all you might need is some water, a map ­and your GPS receiver. Most players will tell you that it's better to over-prepare for a hunt. You don't want to be stuck miles from anywhere and find out you need something you left behind.

Finally, you'll probably want to bring a trinket or two to exchange for anything you might take from the cache once you find it. Most prizes in caches tend to be unique but inexpensive, so it's not necessary to spend a lot of money.

In the next section, we'll look at how to find a typical geocache.


Find That Geocache

A geocache in Antarctica
Photo used under the GNU Free Documentation License

After you've researched a cache, gathered your gear and convinced a friend to tag along with you for the adventure, you're ready to attempt your first hunt. Remember that research includes looking over maps of the area so that you can determine the best approach as well as reading over previous geocachers' experiences with that particular cache. If your GPS receiver only gives you a heading and distance reading, you'll definitely need to do research or you could set yourself up for a major disappointment.

Before you leave, it's always a good idea to call someone and let them know where you are going and how long you expect to be away. Some caches can be in very challenging locations, and if you have an accident or get stuck in a remote area with no cell-phone service, you'll be thankful that someone else knows where you are.


Once you are on foot and heading towards the cache, it's important that you use both a map and the GPS receiver. Some receivers may not hold a signal if you are under heavy tree cover, in a building or underground. If your receiver loses its signal, you'll need the map and a compass to stay on track.

Once you are within the area of the cache, you and your friend can start looking for the container. Your research comes in handy here, too. Some geocachers provide hints about a cache's location and appearance in addition to its coordinates. Geocachers take great pride (and some might say sadistic glee) in finding innovative ways to hide a cache. You might find one dangling from a rope tied to a tall tree branch or wedged behind a nondescript boulder. It helps to put yourself in the perspective of the person who hid the cache in the first place -- look around for places that you would hide a cache if you were in charge.

If you find the cache, you are permitted a short celebratory dance (particularly if you are in a remote area). Open the cache, sign the logbook and write down any thoughts you have about the cache or the trip. Remember to take and leave a prize if the cache has some in it. Return the cache to the same spot where you found it; moving a cache is very much frowned upon.

There's always a chance you won't find the cache at all. Perhaps your GPS receiver isn't accurate enough and the search area is too large. Maybe someone removed the cache or the person who hid the cache may have been too clever. No matter what the reason, it's important to stay positive. Almost every geocacher has a story about not being able to find a particular cache.

Whether you find the cache or not, the next step is to return home and log your experience. You should let the person who hid the cache know about the cache's condition. If you were unable to find the cache, you should tell him. He might have received two or three reports of unsuccessful attempts, which could indicate that someone tampered with the cache.

Whenever you go on a hunt, it is very important to respect your environment. Caches may be hidden in an area that is sensitive to traffic, so try to avoid disturbing any vegetation if possible. Geocachers will tell you that the treasure hunts are a very small part of what makes their hobby so satisfying. They say that the experience of going to new places and appreciating the outdoors is reward in itself.

In the next section, we'll look at what you need to do when you are ready to hide a cache of your own.


Hiding a Geocache

A geocache in plastic container, hidden in tree trunk
Image courtesy Ronald Horii

So let's assume you're an old hand at treasure hunting and have racked up an impressive list of finds. Now you want to hide your own cache for the enjoyment of others. What sort of things do you need to consider?

First you should decide what sort of cache you're going to hide. Geocachers recommend that your first cache be a simple one and that you hide it near where you live. You'll be expected to maintain the cache, so you don't want to put it in a spot you'll have trouble getting to now and again.


When determining the location for your first cache, it is very important to research the area thoroughly. In general, caches should not be hidden on private land unless you have the express permission of the landowner. If you do get permission, you should make sure everyone knows that the cache is on private property. To hide a cache on public lands, you should first contact whatever agency manages those lands to learn about their policy on geocaching. Some organizations have very strict rules for geocachers, while others forbid the practice entirely. It's very important for the pastime as a whole that geocachers are seen as cooperative and respectful.

In either case, you should pick a spot that will appeal to geocachers and give them a new experience. Many geocachers look for impressive, beautiful environments that you might not otherwise visit. To them, the journey is at least as important as the destination, and so finding a unique and interesting cache site is considered an art form.

Once you have secured permission and agree to obey any rules or restrictions, you should look for a specific location within the area you've chosen to hide your cache. Geocaches close to avenues of heavy traffic are more likely to be plundered or tossed away than those that are hidden in more remote areas. A cache should be well hidden, but not impossible to find. The more difficult it is to find, the more likely you'll need to include hints when you list the cache on a Web site.

You should never alter the environment when you hide a cache, nor should you place the cache in such a spot that seekers will have to affect the environment when they look for it. Never bury a geocache or place it in thick brush that others will have to clear. In urban environments, you should carefully consider placement of the cache. You don't want to put your cache in a place that could cause a panic. Geocachers must also consider safety in urban environments and should avoid areas like construction sites or other risky locations.

In the next section, we'll look at how to prepare a geocache container and what you should do once you've hidden it.


Geocaching Containers

The container you select should be of an appropriate size, both for the environment you've chosen and for the contents of the cache. It should also be waterproof and weather resistant, as caches are almost always constantly exposed to the elements. Anything you put inside the cache should be in a zip-top bag. Sensitive items, like logbooks, may need to be double bagged to protect them. Think about the environment your cache will be in -- areas that are subjected to below freezing temperatures or periodic flooding may require additional consideration. You need to label the container so that casual observers and geocachers know what it is. Labels should indicate that it is a geocache and include your contact information. Some geocachers also include a brief note explaining what a geocache is in case a non- player finds the cache.

When you are ready to put your cache in its hiding place, you should take several GPS receiver readings to determine the coordinates for the cache. Write the coordinates on the cache's label with a permanent marker. You should also include the coordinates in the cache's logbook, and don't forget to write them down for yourself to post online later.


After you get back from hiding the cache, you'll need to report it on a geocache Web site. You'll need to include the coordinates for the cache, what the container looks like and any necessary hints (such as where geocachers should park their cars before heading out on foot or signs to look for when searching for the cache itself). Most geocaching Web sites include a way for geocachers to get in touch with you, but you may want to include an e-mail address just in case.

Geocachers who hide their own cache must maintain it if they want the Web site to continue to list it as a viable cache. Over time, you may need to replace the container or add a new logbook if the old one is getting full. You'll also want to take a good look at the environment around the cache to make sure it isn't being adversely impacted by visitors. If you feel that the surrounding area is suffering, you should remove the cache and report it as being offline.

In the next section, we'll look at the sort of things you can find (or put) in a geocache.


Caching In

Many geocaches, like this one found in Germany, ­contain a variety of items, including toys and CDs.
Photo used under the GNU Free Documentation License

At the very least, a physical cache should include a logbook. Hunters can sign and date the logbook to record their discovery. Many hunters will include a short description of their experience, their impression of the cache or the hiding place itself. Usually the cache will also contain a pen or pencil, since it seems most hunters habitually leave their own at home when they set out to find a cache. Small caches that contain only a logbook are called microcaches.

A larger cache might contain any number of small, interesting objects. Some caches have CDs or DVDs in them. Others have small toys or gag gifts. You might find a disposable camera in the cache. You should use it to take a picture of yourself (or your group) and then return the camera to the cache. If the camera is full, you should take a note of it and let the geocacher who maintains that cache know about it.


Of course, there are some things that shouldn't go in a cache. Food is always a bad idea -- it can attract animals or spoil. Weapons, fireworks, alcohol, tobacco and other drugs or any other questionable or illegal object should never be put in a cache. Since geocaching is family-friendly activity, only appropriate items should go into a cache.

A geocache might contain a second, smaller cache. These smaller caches are called hitchhiker caches. When you find a hitchhiker cache, you sign the corresponding logbook (both for the hitchhiker cache and the overall cache) and you take the hitchhiker cache with you. On your next trip to a completely different cache, you bring the hitchhiker with you and place it in the cache once you find it. You should also look for an email address or other instructions on the hitchhiker. There's a good chance the person who originally put the hitchhiker in a cache would like to keep track of its journeys.

Groundspeak, the company that manages, sells trackable tags called Travel Bugs that you can attach to any item you want to place in a cache. Like a hitchhiker cache, hunters can take the tagged item and put it in another cache. The hunter is supposed to log the find by going to Groundspeak's Web site and entering the tracking number into its system, then logging the find on the Travel Bug's homepage. Some people create goals for their Travel Bugs, like a journey across the country from one coast to the other. Geocachers are encouraged to try and help fulfill that goal.

Geocoins are another hitchhiker. Geocachers can create a coin as a personal signature to leave behind at any cache they find. Each geocoin has a trackable ID stamped somewhere on the coin. Geocachers can move these coins from one cache to another, or even just pass it along to someone else. The holder of the coin can use the tracking number to log his experiences before passing it along.

In the next section, we'll look at some of the concerns about geocaching and why some places are restricting it or banning it outright.


Cache Out

Since 2000, the geocaching community has grown from a small group of enthusiasts to thousands of people interested in travel, hiking, sightseeing and treasure hunting. While most geocachers do their best to preserve the environment and respect the property of others, some organizations are concerned that the game could cause a panic or the destruction of carefully maintained sites.

In February 2007, the police department of Portsmouth, New Hampshire investigated what turned out to be a small geocache attached to an electrical panel at a supermarket. A couple of weeks earlier, an advertising agency's marketing ploy had effectively shut down the city of Boston when citizens reported suspicious electric devices placed in odd locations. The Portsmouth police department issued a report, chastising the geocacher for placing the cache in an area that could have caused a panic and warned geocachers that anyone hiding a cache in Portsmouth could be prosecuted. Geocachers have heard rumors that the entire state is considering a ban on geocaching out of the interest of public safety.


Parks are favorite sites for geocachers, but some have a perpetual ban on the game. The National Park Service doesn't allow geocaching on any of the lands it administers, because of the need to preserve fragile environments. Parks Canada has a similar position, though they refer to it as an interim policy while they decide on a more permanent set of rules. Geocachers are not allowed to hide any physical caches on land overseen by Parks Canada.

Many state parks will allow geocaching with some limitations. Park policies can vary widely between locations, so it's always important to contact the parks directly when placing a cache. Some parks may only require that you register the cache with them so they know where it is, while others have specific rules dictating where you can and can't put a cache. Some geocachers have followed the philosophy that hiding a cache isn't a problem until someone makes it one, but most argue that such an attitude is harmful for the hobby and casts all geocachers in a bad light.

For more information about geocaching, check out the links on the next page.


Lots More Information

Related Articles

More Great Links


  • "Development of a Final Policy on Geocaching in Protected Heritage Areas Managed by Parks Canada". Parks Canada.
  • Geocacher University
  • "Reference: GPS Scavenger Hunting," Portsmouth Police Department News Release, February 4, 2007.
  • Sloan, Gene. "Philadelphia, other locales 'cache' in." USA Today. May 31, 2007.­2007-05-31-geocaching_N.htm