User's Manual

SPSx50 Modular GPS Receiver User Guide 49
Setting up the Receiver 5
recommends that each end is clearly marked GPS and Radio respectively, to ensure
that at each daily setup the GPS and Radio antennas are mounted at the same location.
Switching antennas by mistake introduces a position error in all resulting
measurements. The equipment required to fabricate a T-Bar can be purchased in any
reputable hardware store. Take care to ensure that the T-Bar cannot rotate after
construction. Rotation of the T-Bar can introduce a position error into all subsequent
measurements.
On the upright post, either mount a bracket to which the GPS receiver can be
mounted, or place a lock box with ventilation on the post, in which the GPS receiver
itself can be secured.
Each day, mount the GPS antenna on the GPS end of the T-Bar and the radio antenna
on the Radio end of the T-Bar. Connect the Radio and GPS Antenna to the receiver
using the appropriate cables. In these scenarios, the receiver will operate from its own
integrated battery or from an external 12 V battery through use of the 12 V crocodile
clips cable provided with the receiver. If AC power is available, this can be used,
however the heat generated by the charging process and the radio transmitter
increases the need for good ventilation around the receiver to dissipate the heat.
In these scenarios an SPSx80 smart GPS antenna is also often used, in which case the
receiver only needs to be mounted on the T-Bar and optionally connected to an
external battery or radio unit.
The benefit of the T-Bar setup is that it is easy to ensure that the base station is set up
daily in the exact same location each day in terms of position and height, that will
eliminate the errors typically associated with daily setup on a tripod (wrong antenna
heights, not setup over the point, setup in the wrong location etc.)
Figure 5.2 System set up on a T-bar