User's Manual

Using GPS
22 GeoExplorer 2005 Series Getting Started Guide
Getting a clear view of the sky
To receive signals from GPS satellites, the receiver must have a clear
view of the sky. GPS does not work indoors. Hold the handheld with
the screen toward you. The internal antenna is located above the
screen under the Trimble logo. You do not have to hold the handheld
perfectly level, but keep the antenna facing upward, not downward or
sideways.
Anything that blocks light also blocks signals. Satellite signals can be
blocked by people, buildings, heavy tree cover, large vehicles, or
powerful transmitters. GPS signals can go through leaves, plastic, and
glass, but these all weaken the signal.
GPS COM ports
The integrated GPS receiver has three COM ports for communicating
with software on the handheld and with external devices.
Using GPS is as simple as opening the appropriate GPS COM port.
Each port is used for a particular type of communication:
Note – COM1 is a standard serial port that connects to external devices.
For more information, see Using the Optional Serial Clip, page 68.
Port Function Description
COM2 NMEA Outputs NMEA-0183 messages. NMEA is a standard
GPS communication protocol used by most GPS
applications.
The handheld outputs the following NMEA messages:
GGA, GLL, GSA, GSV, RMC, VTG, ZDA. All messages are
output at a one second interval.
COM3 TSIP Outputs and receives TSIP messages. TSIP (Trimble
Standard Interface Protocol) is used by Trimble GPS
applications, and is also supported by some other GPS
applications.
COM4 Real-time Receives RTCM real-time correction messages. If you
are using an external correction source connected to
COM1 or a Bluetooth port, the corrections must be
redirected to COM4. For more information, see Using
real-time corrections from other sources, page 28.