ITC 220 Base Station, Locomotive & Wayside Radio Transceiver Field Service Guide PN 0046300120 Rev. A
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Be aware of any potential transient obstructions.
Always note the format of the GPS coordinates (for example, decimal degrees or decimal minutes)
E.2.2 DETERMINE GPS COORDINATES
If you have not already determined the GPS coordinates through a field survey, then it is possible to do so using the
radio’s internal GPS receiver. The GPS coordinates are of the GPS antenna and not the position of the radio.
GPS self-survey
GPS survey is a special and important case of configuration that does not fit neatly into any category. It is an installation
procedure that affects configuration.
Base Station and Wayside Transmitters are equipped with internal GPS receivers. The GPS provides the precision timing
required to synchronize the network.
Configure the GPS to use timing mode since it provides the most precise and reliable timing possible. In timing mode,
the GPS can provide timing signals with a single GPS satellite in view. However, timing mode requires that the radio
provides a position to the GPS. There are two ways to provide a position to the GPS:
Use the command line to configure surveyed position obtained offline.
Allow the GPS to determine its own position.
The method used depends on which fits better into the user’s workflow.
Surveyed position obtained offline
One way to configure the transceiver GPS is to obtain the survey position offline, then use the
LOCATION
command to
provide the position and instruct the transceiver GPS to use that position information.
Using this method, the user:
Must maintain a database of position coordinates for all fixed installations.
May configure the GPS by issuing the command manually or by including the command in a CIM script file.
The following example shows the use of the LOCATION command.
+LOCATION,47:28.381N,122:14.013W,15.7
+POS,SOURCE,MANUAL
+POS,TIMING,ON
+TIMESYNCH,GPS
+
GPS determines its own position
The second method allows the GPS receiver to determine its own position. This method adds an additional step to the
transceiver installation process.
The advantages of this method include: