Data Hacking

FIGURE 11-4: A far bigger search area!
The Final 20 Yards
Chapter 11 — Hacking Geocaching
You’d think that after getting to within 20m or so of your desired location with a GPS, the final
few yards would be a walk in the park (pun intended!). After all, GPS manufacturers boast
superb accuracy nowadays, so in theory you should be able to walk right up to the geocache
and reach right under that log or in that bush and retrieve your prize. The truth is that, all
things being equal, the final 20 yards or so can be the most difficult. Here’s why:
Your GPS isn’t 100 percent accurate! It doesn’t know where you are, it estimates where
you are. There is a big difference. Remember that this is true of the GPS receiver or the
person that set the cache, and if the conditions aren’t good, the error experienced by the
person setting the cache compounds any error you are experiencing.
Playing the averages: As you travel, GPS in hand, the device is averaging your position
all the way. The further you are from the cache, the less all these averaging errors matter
because when you are, say, 1,000 yards from the cache (or 100 yards for that matter), the
direction of travel arrow on your GPS is still going to point in the general direction you
have to go.
261