PDA User Manual

Chapter 6: Settings
GPS (Global Positioning System) Settings
Ikôn Rugged PDA (Windows Mobile 6.1) User Manual 157
AGPS (Assisted Global Positioning System) Tab
To determine your location, a GPS module receives data from three or more GPS satellites
in fixed orbit around the Earth. The GPS module triangulates your location based on the
time it takes for signals to get to and from the satellites. This works well in fairly clear areas
– outdoors, for example. However, if you’re attempting to triangulate your location in city
centres where signals bounce off tall concrete buildings or from within a building, the GPS
module will have greater difficulty calculating a fix.
AGPS reduces Time To First Fix (TTFF) and increases the likelihood of finding and keeping
a fix in poor coverage areas such as indoor sites. AGPS downloads satellite ephemeris (or-
bital) data to the Ikôn periodically through WiFi or WWAN. The downloaded data is used
by the GPS module to speed the process of getting a fix.
Update
• Click on the Update button to download Extended Ephemeris (EE) files from a secure
host on the internet using any interface that has an internet connection (WWAN or
WiFi). These files contain several days worth of ephemeris (orbital) data that can be
used if the satellite’s broadcast ephemeris is not available.
The Status field above the Update button displays the progress of the download, and once
successfully downloaded, the Status field will read Idle.