Thales Z-Max Operation And Application Manual page 162

Kinematic Initialization
Prior to performing any feature location with the rover system, the receiver must first
go through an initialization process. The initialization process is required to produce
highly precise positions. Prior to initialization, the rover system will compute positions
at a degraded level of accuracy. The accuracy prior to initialization could be anywhere
from 0.15 meters (0.5 ft) to a couple of meters (several feet). The initialization process
is required to fine-tune the rover system. Once initialized, the rover system will
function at its specified level of accuracy until initialization is lost.
Let's devote a few sentences here to the technical aspects of the initialization
process. In order to accomplish centimeter-level positioning with GPS, you must
collect enough data to calculate a set of parameters termed integer ambiguities.
During the initialization process, you are collecting the data required to calculate the
integer ambiguities. Once the integer ambiguities have been calculated, your current
location can be determined very quickly and very precisely. Once the integer
ambiguities are solved, the position of your location can be computed with only an
epoch or two of data. In addition, once the integer ambiguities are computed, they
stay the same (fixed) as long as you maintain lock on at least five satellites. If you
happen to lose lock on satellites due to an obstruction and go below the five-satellite
threshold, the integer ambiguities will be lost and must be calculated again, i.e. you
must initialize your kinematic survey again. All data collected prior to losing the
initialization is not affected by your loss of initialization.
Once the rover is initialized, each point of interest need only be occupied for a
minimum of one epoch. However, the accuracy will improve if you occupy the point for
multiple epochs. For example, as the initialized rover system moves around the job
site, the rover system is continually computing positions at the 0.02 - 0.05 meter
(0.07 - 0.15 ft) level. If you stop in one location and observe for 8 seconds or more,
your precision will improve to 0.01 - 0.03 meters (0.03 - 0.10 ft).
Initialization of your kinematic survey can be accomplished in several ways.
1. On-the-fly
2. By performing a static survey
3. On a known point
Survey Preparation and Execution 139