Data Hacking

172 Part III — Data Hacking
Manual Waypointing
A manual waypoint is one that you enter into the GPS for a location that you are not currently
at. For example, before you leave home, you might enter the waypoint of the parking lot at your
destination or perhaps the geocache that you are looking for (see Figure 8-10).
FIGURE 8-10: Manual
waypointing
To enter a manual waypoint, you need to know the coordinates of the location to which you are
heading. For this you need a map of some kind or some other repository of coordinates (a map,
geocache listing, points of interest, etc.).
Be very careful when manually entering waypoint information into your GPS because a small
numerical error can translate into a massive error on the ground! In addition, make sure that
you’re using the appropriate datum for the coordinate system being used (for degrees/minutes/
seconds, degrees/minutes, and decimal degrees, use WGS84). Using the incorrect datum can
cause inaccuracies of several hundred meters.
Coordinates form the fundamental aspect of navigating with a GPS other than using dead
reckoning (where you follow a path and a bearing for a certain distance over a certain amount
of time), and getting comfortable with using them is the first step to really using GPS properly.
On-the-Spot Waypointing
With on-the-spot waypointing, you travel to a place and waypoint that particular location,
storing the waypoint in your GPS. This stores the location that is displayed by the GPS into
the memory of the device. You can then navigate back to this spot later. For example, you could
waypoint the location of your car before going off in search of a geocache so that you are sure
to find it on the way back).
Routes
Routes are path data that is stored in the GPS. A route is a series of waypoints contained in the
GPS that form a path of travel, similar to the connect-the-dots activity found in children’s
activity and puzzle books.