(2) The stations that are selected for survey must have an unobstructed view of the sky 15, or
greater above the horizon during the observation window. An observation window is the period of time
when observable satellites are in the sky and the survey can be successfully conducted.
(3) It is critical for a static survey baseline reduction or solution that the receivers simultaneously
observe the same satellites during the same time interval. For instance, if a receiver observes a satellite
constellation during the time interval 1,000 to 1,200 and another receiver observes that same satellite
constellation during the time interval 1,100 to 1,300, only the period of common observation (1,100 to
1,200) can be processed to formulate a correct vector difference between these receivers.
(4) After completing the observation session, the GPS signals from both receivers are processed
in a computer to calculate the 3D baseline vector components between the two observed points. From
these vector distances, local or geodetic coordinates may be computed or adjusted.
(5) Static baselines may be extended from existing control using the control densification
method. This method includes networking, traverse, spur techniques, or combinations thereof. Specific
requirements are normally contained in project instructions.
(6) Specific receiver operation and baseline data postprocessing requirements are manufacturer-
dependent. The user should consult and study the manufacturer's manual (including the baseline data
reduction examples).
(7) Accuracy of static surveys usually exceeds 1 part per million (ppm). Static is the most
accurate of all GPS processing methods and can be used for any order survey.
b. Stop-and-Go Kinematic Surveying. Stop-and-go kinematic surveying is similar to static
surveying in that each method requires at least two receivers simultaneously recording observations. A
major difference between static and stop-and-go surveying is the amount of time required for a receiver
to stay fixed over a point of unknown position. In stop-and-go surveying, the first receiver (the home or
reference receiver) remains fixed on a known control point. The second receiver (the rover receiver)
collects observations statically on a point of unknown position for a period of time (usually a few
minutes) and then moves to subsequent unknown points to collect signals for a short period of time.
During the survey, at least four (preferably five) common satellites need to be continuously tracked by
both receivers. Once all required points have been occupied by the rover receiver, the observations are
postprocessed by a computer to calculate the baseline vector and coordinate differences between the
known control point and points occupied by the rover receiver during the survey session. The main
advantage of this method over static surveying is the reduced occupation time required over the
unknown points. Because stop-and-go surveying requires less occupation time over known points, the
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