Viavi 87339, Operation Manual

Page: 68 / 198

Testing
3 - 27
3.2.14 GPS RX Function Window
The Internal GPS Receiver may be used to obtain a current Almanac, location and UTC
for use in simulations. This removes the requirement for a periodic manual Yuma text
format almanac (*.alm), download from the U.S. Coast Guard website and subsequent
upload to the GPSG-1000 memory.
When testing a GPS receiver, if the simulated position is too far from the last acquired
position or the simulated time and date are to far from the last acquired time and date the
receiver will initiate a warm start which, dependent on receiver type, will take longer than
a hot start to acquire a position fix. As the last location would likely be the current
position, the latitude and longitude from the internal GPS receiver may be used by the
simulation, which would then allow the receiver under test to hot start.
Fig. 3-16 GPS Receiver Window
Control Component Description
GPS Receiver Selects internal GPS receiver.
Load Almanac from
GPS Rx
Loads almanac from internal GPS receiver. Download status is
displayed in the Almanac Status display window.
Note: It may take up to 20 minutes for the data from the first
SV to be downloaded, and it may take up to 30 minutes to
complete a download of almanac data from the entire GPS
constellation
GPS Receiver Reset Initiates a Cold Boot of the internal GPS receiver.
Record Trajectory When activated this control begins recording trajectory data
produced by the internal receiver. The recording will continue
until the Stop Recording button is pressed. The data will be
stored in a file with the following naming convention
MMDDYYYY_HHMMSS.nme when the stop recording button is
pressed.
NOTE: The Record Trajectory function should only be initiated
once a 3D fix has been achieved by the receiver.