ashtech Z-FX, Operation And Reference Manual

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Operations 63
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occupation. Each operator follows this point and time schedule throughout the day,
assuming all other operators are doing the same. If all is going well, each operator
will be at the designated points at the designated time, and simultaneous data
collection will occur, establishing the baselines between all points being observed.
Kinematic Surveying
The kinematic method of GPS surveying utilizes a completely different approach to
determine the carrier phase ambiguities compared to other methods. With kinematic
surveying, the carrier phase ambiguities are determined by occupying a previously
measured baseline (occupying two known points). Since the positions of the occupied
points are already known, the carrier phase ambiguities can be determined very
quickly. This process is commonly termed the initialization of a kinematic survey and
requires approximately 5 minutes to perform. Once the carrier phase ambiguities
are determined, they will not change unless the receiver loses lock on the
satellites. This is the key fact which defines kinematic surveying. Since the carrier
phase ambiguities are already known, an accurate position for unknown points can be
determined in a very short time (seconds). However, lock must be maintained on at
least four satellites at all times.
A very effective procedure for high productivity is a combination of the rapid static and kinematic
methods of surveying. If for some reason the number of satellites locked falls below four, the
kinematic survey must be re-initialized. This can simply be done by performing a rapid static survey
on the next unknown point. This will automatically reinitialize the kinematic survey.
The advantage of the kinematic surveying method is increased productivity, with
accuracies comparable to static surveys. Many points can be surveyed in a very short
period of time when occupation times are very short. A significant disadvantage is the
logistics problems of moving from point to point without losing lock on satellites.
Trees, buildings, and other obstructions can make it difficult or impossible to
maintain lock on at least four satellites as the receiver is transported from point to
point. The risk occurs where the user is not aware that while moving from one point
to the next, loss of lock occurred momentarily. Without re-initialization, the data
collected after loss of lock will be useless. This is why utmost care must be taken
when performing a kinematic survey.
Use the kinematic method when high productivity is required. The best results will
occur when the kinematic survey is performed in an area with little obstruction of
view to the sky and when points are relatively close together. Do not perform a
kinematic survey on baselines longer than 10 kilometers. The longer the baseline, the
higher the risk of failure.