CHAPTER 3. CONF
I
GUR
I
NG THE ASTERX SB
I
3
3.2 How to measure and compensate for the
Antenna Lever Arm
The antenna lever-arm is the relative position between the
I
MU reference point and the GNSS
Antenna Reference Point (ARP). The
I
MU reference point is clearly marked on the top panel
of the receiver. Refer to the data sheet of your GNSS antenna for the exact location of the
ARP.
I
t is important to compensate for the e
ff
ect of the lever arm, otherwise the receiver may
not be able to calculate an accurate
I
NS position. The higher the accuracy of the lever-arm
dimensions, the better the accuracy of the
I
NS solution calculated by the receiver. As shown
in Figure 3-5, lever arm o
ff
sets can occur in three dimensions.
Figure 3-5:
Example of the relative
I
MU/antenna position in the vehicle
’
s frame
(in blue).
I
n this example, the lever arm X and Y components are equal to X
’
and Y
’
(positive), while the Z component is Z
’
(negative) + 1.7cm.
Values representing the relative position of the main antenna ARP with respect to the
I
MU
reference point in the three dimensions of the vehicle reference frame can be provided to the
receiver in the web interface under GNSS/
I
NS > External Sensor Setup as shown in Figure 3-6.
Note that in order to correctly reference to the antenna
’
s ARP, it is necessary to compensate
for phase center variations. This can be done in the web interface by going to GNSS/
I
NS >
Position and selecting the correct antenna type in the
’
Antenna
I
nformation
’ fi
eld.
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