Winter 2006 Forward to a Friend



travelers and explorers have navigated land and water using tools available for their times. The sun, the stars, astrolabes, compasses, gyroscopes, chronometers, cross-staffs, sextants, charts, maps, radio, radio detecting and ranging (radar), Loran hyperbolic navigation and, today, satellite-based electronic Global Positioning System (GPS) have helped wanderers plot and plod from point to point.

GPS was initiated in 1973 by the U.S. Department of Defense as the Navigation Satellite Timing and Ranging (NAVSTAR) system. NAVSTAR used 24 satellites to aid in pinpointing locations around the world. For national security reasons, an intentional error called selective availability (SA) was programmed into GPS, limiting accuracy for civilians to about 300 feet ? about the size of a football field. On May 2, 2000, SA was disabled, improving accuracy to within six to 20 feet for everyone who wanted to use GPS technology.
Photo courtesy of NOAA


GPS satellites each weigh about a ton and are 17 feet across with their solar panels extended. Solar powered with battery backup, they have life expectancies of about 10 years, when they’re replaced. The 24 satellites orbit the earth at about 12,000 miles twice every 24 hours. To do this, they’re cruising through space at about 7,000 miles per hour.

Location and timing are critical to the information relayed by the satellites, and the likelihood for errors is constant. GPS has been made more sophisticated over the years to counter those errors, and GPS receivers reflect the system’s improved technology.

DIFFERENTIAL GPS (DGPS) – The U.S. Coast Guard operates a series of towers that help to correct the satellite system’s errors by adding the constant of fixed (land-based) checkpoints. DGPS technology improves accuracy to between one and five meters (about three to 16 feet).

WIDE AREA AUGMENTATION SYSTEM (WAAS) – The Federal Aviation Administration has implemented a network of 25 ground reference stations in the United States, Canada and Mexico. These feed information to a master station that broadcasts corrected latitude, longitude and altitude information. WAAS technology improves accuracy to within three meters (10 feet).

GPS Stash Hunt

A computer consultant named Dave Ulmer wanted to test the accuracy of the GPS signals. On May 3, 2000, he hid a bucket in the woods near Beaver Creek, not far from Portland, Oregon, and he measured the bucket’s coordinates with a GPS unit. Ulmer then posted its coordinates on the Internet for a user’s newsgroup and called the search for it the “Great American Stash Hunt.”

The bucket contained a number of prizes and a logbook for seekers to sign. For those who would find the stash, there was only one rule: “Take some stuff. Leave some stuff.”

It only took a few days for Internet users to find the stash and talk about it online. Other stashes were hidden, and by the end of the month, the term geocache was coined to describe the hidden “treasure.”

The word geocache combines geo (for “earth”) with cache (for “a hiding place” or for “computer storage”). Geocaching was adopted as the official name of the game on May 31, 2000.

You might consider geocaching a sport or a game. Either way, the number of its participants has grown exponentially since the beginning of the millennium. Today, there are more than 200,000 active caches in 218 countries around the world.

Photo courtesy of Garmin
The Game

Geocaching has a number of guidelines – not rules, as such. You need very few things in order to play.

Basically, someone hides a box containing treasures (books, CDs, videos, key chains – limited by imagination only), noting the coordinates of the hiding place with a GPS unit. The hider then posts those coordinates on the Internet – is one of the sites on which to post and find locations.

Seekers who want to look for hidden treasure in the area of the hiding place will find the posted location on the Web site and use his or her own GPS unit to try to find it. When the seeker finds the hiding place, he or she signs the enclosed logbook and swaps treasure. The seeker also can log the find on the original site on which the coordinates were first listed.

It sounds simple. But terrain and the nature of the area in which the treasure is hidden can make the seeking difficult.

The Web site and a number of reference books on geocaching list variations of the game. Time is the mother of invention for geocaching, and the number of variations on the theme of high-tech hide-and-seek continues to grow.


MULTIPLE CACHES – The seeker is required to go to at least two locations prior to finding the hidden treasure.

VIRTUAL CACHE – There is no hidden treasure at all, but a unique object like a monument to be found.

SHUTTERSPOT – Participants try to find and log by latitude and longitude the exact spot where a photographer stood to take a posted photograph.

GEOSNAPPER™ – Nextel camera phones with proper software “geotag” photos, which are categorized, searched and shared on

GEODASHING – Participants around the world race to find randomly selected waypoints, or dashpoints. Whoever finds the most dashpoints wins.

golf ball GEODASHING GOLF – Players use GPS receivers to navigate to 18 randomly placed waypoints (or nine in a short course). The closer to a given waypoint, the lower the score, and the lowest score wins.

MINUTEWAR – This game of capture-the-flag divides local maps into squares that are one minute of longitude wide and one minute of latitude long. Each square contains a virtual flag. Participants start at the same time to visit these spots to capture the flags.

BENCHMARK HUNTING – More than 700,000 U.S. National Geodetic Survey markers can be found in the United States. Find nearby locations at

TRAVEL BUGS – Players move these trackable “hitchhikers” from place to place. Their logbooks tell their stories.

THE DEGREE CONFLUENCE PROJECT – The project’s goal “… is to visit each of the latitude and longitude integer degree intersections in the world, and to take pictures at each location.” Photos and stories are posted at

EVENT CACHES – The listings have time elements that bring participants together for designated activities, such as picnics.

MICRO-CACHES – These feature tiny containers, which are better to hide in an urban setting to avoid alarming people.

AUTO RALLIES – Rallies already require a sense of direction, so a GPS receiver is likely to be part of the equipment. Navigation exercises are especially fitting for off-road events.


As with any outdoor endeavor, your approach and the correct gear can be critical for comfort and safety while hiding or seeking a geocache. Organize and be prepared!

Here are some of the things that will help make your geocaching experience a good one:

HAVE SOMEONE WITH YOU. The “unknown” can be dangerous – even if that unknown is as simple as a hole into which you’re about to step. Two sets of eyes are better for keeping track of where you are, especially when one set is fixed on the coordinates of a GPS unit.

Map and GPSBE AWARE OF YOUR SURROUNDINGS. Even when you’re with someone else, watch for thorns, low-hanging branches, cliffs, unfriendly wild animals and other normal natural “hazards.”

CARRY AND DRINK PLENTY OF WATER. Depending on the location’s climate, dehydration can be more or less of a safety factor, but it’s always a factor. For long, involved searches, a water filtration system might be in order.

TELL SOMEONE WHEN AND WHERE YOU’RE GOING. Mom’s admonishment to “call when you get there” still applies, only it doesn’t have to be Mom. When traveling in a remote location, anything can happen, so make sure someone knows your intentions and approximate schedule.

MARK YOUR CAR’S LOCATION AS A WAYPOINT ON YOUR GPS UNIT. Like Hansel and Gretel’s fabled bread crumbs, a waypoint (which is like a flag on a map) will help mark the way back. The difference is that GPS uses satellite navigation, which is more accurate and also less likely to be eaten by animals than bread crumbs.
HAVE THE NECESSARY HIKING GEAR, ESPECIALLY WHEN YOU’RE TAKING THE PATH LESS TRAVELED. Outdoor gear for geocaching involves more than a reliable GPS receiver (and power cord for use in your vehicle). Proper gear includes:

• Map of the area and compass (these are of critical importance)
• Weather-appropriate clothing
• Flashlight and batteries
• Batteries for your GPS receiver
• Notepad and pen in a waterproof bag
• Knife
• First-aid kit
• Matches
• Sunscreen/sunglasses
• Signal mirror
• Whistle



  • LATITUDE AND LONGITUDE – location of the receiver on earth’s coordinates
  • ALTITUDE – distance above or below sea level
  • COMPASS DIRECTIONS – north, south, east and west
  • MAPPING – from maps with no details (but user-created waypoints, routes or track logs) to base maps that show major roads and geographic features to highly detailed maps that can be downloaded from mapping CDs


  • COMPASS DIRECTIONS – automatically reset from magnetic north to true north
  • SWITCHABLE MAP DATUMS – the ability to switch to different map datums (starting reference points) to match the maps being used
  • MEMORY – just like computers, receivers with greater memory provide more functions and added detail
  • ANTENNA CHOICE – built-in patch, Quad Helix, flip-up patch and externally mounted antenna systems to meet users’ needs
  • DISPLAYS – black-and-white or color

Geocaching WomanThe Sum of Geocaching

Geocaching is simple in concept, but involved in its pursuit. It integrates the high technology of computers and hand-held electronic equipment reading signals from satellites with some of the most relaxing and beloved of pastimes – being outdoors, hiking and discovering new things about the world around us.

For more information, visit and (“About GPS”).