User's Manual

PDL-4 A.C.ID-M System (with GPS) User Guide
Page 25
GPS User Guidelines
Buildings, foliage, and people can block signals from GPS positioning satellites. The ideal location using GPS
is a wide-open space, with an unobstructed view of the sky in all directions. Make sure the unit has an
unobstructed view of the sky before trying to obtain a fix.
Trying to obtain GPS readings in poor coverage areas may result in longer fix times and reduced PDL-4
battery life. To maintain battery life when locating in an inner city area, or any other area where poor
coverage is to be expected, always select the GPS OFF option from the user preferences menu.
Do not leave the unit idling (waiting for a fix to be displayed) in the Display Fix mode for more than two
minutes, as this will drain the battery.
Because GPS positioning satellites orbit the globe the actual number available for position fixing varies
during the day. Long term testing has shown that occasional signal dropouts can occur where no coverage is
available, regardless of location. As satellites appear over the horizon at least every 30 minutes, it is worth
trying to obtain a position fix in difficult GPS locations at different times of the day.
The following guidelines will help in establishing consistent PDL-4 GPS performance.
• Avoid having people crowd around the GPS antenna during a fix.
• Hold the unit away from the body with the face of the GPS antenna flat to the sky.
• Keep the receiver stationary during a fix, as even slight movements will affect the signal levels from the
satellites reaching the antenna.
• Poor or non-existent coverage is to be expected when locating in built-up inner city locations.
• Keep cell telephones, hand held radios and laptop computers away from the GPS antenna during use.
• If the receiver is transported several hundred miles or more it will require a manual cold start command to
re-acquire its new position; this may take several minutes.
• The cold start key can be used to reset the GPS receiver at any time, but frequent use is to be avoided
as fix times are extended and battery life reduced.
• PDL-4 GPS performance is comparable with commercial hand held units, but varying
satellite patterns in the sky will favour different types of GPS antenna so direct comparison may be
misleading.
The GPS performance is not affected by cloud cover, rain, or temperature.
The GPS will not work indoors.