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Geocaching for Blind Participants

The issue of the "last 50 feet"

GPS can be a major benefit to blind and sighted people alike. Whereas sighted users have many alternatives in the environment to GPS information, blind people have few alternatives. GPS accuracy varies from 10 to 100 feet and it averages about 30 feet. This isn't much of a problem for sighted users because once they are within 100 feet of a destination, they can see the desired target,) sign or building, certainly within 50 feet. A blind person however has to use ingenuity or physically explore that last 50 feet to find a specific item. It is so cool to navigate to and fro independently for tens of blocks or miles and then that darn last 50 feet is harder than the rest of the trip combined if you cannot see.

Geocaching is a worldwide game played by millions of people. Users go to, pick a city and then enter the relevant lat/lon for a specific cache from the site into a GPS device. This game relies on the concept that one can see visual clues in that crucial last 50 feet. The site provides the lat/lon that gets the user to the vicinity of the geocache which includes a clue as to the specific location. Those clues depend on seeing. The cache could be a poem written on a plate underneath a phone booth or within a small scroll of paper inside a film canister in a planter box. You have to be able to see these things to make sense of the clues.

This game imitates reality because the blind person cannot see the doorway to the restaurant or portico for the government building that is obvious visually. We have to ask a passer-by or find other ways to sort out this last 50 feet.

With this in mind, Sendero has redesigned the game of Geocaching so a blind GPS user can participate independently rather than having to have a sighted guide. We set GPS points at locations that can be associated with either environmental clues or with points in the commercial POI database. For example, we set a user POI in front of the bakery called Simple Simons. We record a voice tag with that point that says, "This is a very simple point to find. You must say his name before he will tell you what to do." This clue won't make sense until you get close to the bakery and hear the commercial point trigger, "Simple Simon Bakery." Then, the light comes on. The user sniffs for the bakery or asks someone where the entrance is and they have success. Beats the heck out of feeling for a film canister within 900 square feet of bushes.

Setting up a GPS Treasure Hunt:

The following instructions pertain to the BrailleNote or Braille Sense products. Much of this could be done on a Trekker Breeze other than entering a lat/lon from the site, which cannot be done on the Breeze.

  1. Choose businesses which are in the commercial POI database or which can be identified by a description or sense other than sight.
  2. Come up with a verbal voice tag or text clue to add to this point keeping in mind how to direct the user to the point within that last 50 feet. The user is of course allowed to ask a sighted passer-by for assistance as a normal part of independent navigation.
  3. Have no more than one point per block or at least 500 feet apart.
  4. Choose streets or environments which are safe to travel and that have low ambient sound levels. not too loud if possible.
  5. Provide a mechanism for the user to prove he or she found the point such as acquiring a business card from the establishment assuming it is open. A camera phone could be used to take a picture in front of the point.
  6. If there are multiple people working together and not everyone has a GPS unit, trade off the device every point or couple of points. It may also be necessary to use an external speaker if multiple people are going to hear speech from the device.
  7. If there are multiple groups, require each group to start off with a different point. It usually then works to let groups find the nearest points rather than requiring that they search in order.
  8. If the points are created on one machine, take into account transferring them to other machines. It may be useful to set all points as "User Private" points.
  9. Do not enter POI names which will give away the POI. Use generic numbers instead.

Techniques for finding points:

  1. Remember that one must walk in a constant direction for 50 feet or so before the relative GPS directions are accurate.
  2. Choose the target point, set it as the destination and listen to the clue.
  3. Use the 3 indicators to locate the point, the distance, compass direction and name of the street. Do not rely on the clock face direction as much as the compass direction.
  4. Once you are within 50 feet of the point, stop and reconsider the clue. Check the nearby commercial points of interest to see if any names are related to the clue. If not, move closer and try again.

Have fun and remember that Geocaching is a great way to teach GPS navigation, which in turn can provide location literacy to people who are blind and visually impaired.

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