Ag Leader GPS 1600 Operators Manual - Manual (Page 10)

6 PN 2006346 Rev A
GPS O
PERATION
The GPS receiver is always operating, regardless of the DGPS mode of operation. The following
sections describe the general operation of the receiver’s internal GPS receiver.
A
UTOMATIC
T
RACKING
The receiver’s internal GPS receiver automatically searches for GPS satellites, acquires the signals, and
manages the navigation information required for positioning and tracking.
R
ECEIVER
P
ERFORMANCE
The receiver works by finding four or more GPS satellites in the visible sky uses information from the
satellites to compute a position within 2.5 m. Since there is some error in the GPS data calculations, the
receiver also tracks a differential correction. The receiver uses these corrections to improve its position
accuracy to better than 0.6 m.
The two main aspects of GPS receiver performance are 1) satellite acquisition, and 2) positioning and
heading calculation.
When the receiver is properly positioned, the satellites transmit coded information to the antenna on a
specific frequency. This allows the receiver to calculate a range to each satellite. GPS is essentially a
timing system. The ranges are calculated by timing how long it takes for the signal to reach the GPS
antenna. The GPS receiver uses a complex algorithm incorporating satellite locations and ranges to
each satellite to calculate the geographic location and heading. Reception of any four or more GPS
signals allows the receiver to compute three-dimensional coordinates.
D
IFFERENTIAL
O
PERATION
The purpose of differential GPS (DGPS) is to remove the effects of atmospheric errors, timing errors,
and satellite orbit errors, while enhancing system integrity. Autonomous positioning capabilities of the
receiver will result in positioning accuracies of 2.5 m 95% of the time. In order to improve positioning
quality to better than 0.6 m 95%, the receiver is able to use differential corrections received through the
internal SBAS demodulator.
A
UTOMATIC
SBAS T
RACKING
The receiver automatically scans and tracks SBAS signals without the need to tune the receiver. The
receiver features three-channel tracking that provides an enhanced ability to maintain a lock on an
SBAS satellite when more than one satellite is in view. This redundant tracking approach results in more
consistent tracking of an SBAS signal in areas where signal blockage of a satellite is possible.