Hioki PW9005 Instruction Manual page 50

16
Chapter 4 PQ3198 GPS Positioning and Time Correction
PQ3198 time correction error
Once GPS time correction has been enabled, the maximum reciprocal rela-
tive time error for the PQ3198 is 4 ms. However, larger errors are possible
with large DOP values, which indicate that positioning is subject to a low
level of reliability, even when the PW9005 has calculated its position.
Antenna installation
When turning on the PW9005 for the first time or using it for the first time
after a certain period of time has passed, the amount of time it takes to cal-
culate its position varies significantly with the antenna location and GPS
satellite positions.
In order for the PW9005 to acquire GPS satellites quickly, it is best for the
antenna to be positioned with a clear view of the overhead sky with no
obstructions nearby. By contrast, the unit's ability to acquire satellites may
be compromised when the antenna is positioned such that its view of the
overhead sky, and therefore of the constellation of GPS satellites, is
obstructed, for example due to placement in a forest or on a street sur-
rounded by tall buildings.
When turning on the PW9005 for the first time or using it for the first time
after a certain period of time has passed, it is particularly important to test
reception of satellite signals by placing the antenna in a location where it
has an unobstructed view of the entire sky. If the antenna is placed so that
it has only a limited view of the overhead sky, for example indoors or on a
veranda, the unit may be unable to detect its position, even after dozens of
minutes have passed since it was turned on.
Similarly, if the antenna is placed next to a large obstruction such as a
building, it may initially acquire satellites only to lose reception later due to
the satellites' movement. If the PW9005 is unable to detect its position for
an extended period of time while recording data with the PQ3198, the
instrument may cease to be able to perform time correction (see "4.2 Time
Correction Processing" (p.17)). When you plan to record data for an
extended period of time, it is recommended to place the antenna so that it
has as unimpeded a view of the overhead sky as possible.
GPS rollover problem
Generally, GPS receivers have a rollover problem. This is a phenomenon
such that the date information will be reset after a certain period of time,
resulting in a false date output.
The system time of the device rolls over at 23:59:59, June 16, 2035. Sub-
sequently, the time correction will not be performed correctly.
Leap second
Model PQ3198 does not deal with leap seconds. When the PQ3198 is not
in [SETTING]
tion range, resulting in a GPS time error (GPS Err) and failure of the time
correction function. When the PQ3198 is in
tions will operate properly.
mode, a leap second will exceed the millisecond time correc-
HIOKI PW9005A980-06
[SETTING] mode, time correc-