The process of resolving the integer ambiguities is called initialization and may be done by sitting up both receivers at each end of a baseline whose coordinates are accurately known
In subsequent data processing the coordinates are held fixed and the integers determined using only a signal epoch of data
These values are now held fixed throughout the duration of the survey and coordinates estimated every epoch provided there are no cycle slips
The initial baseline may comprise points of known coordinates fixed from previous surveys by static GPS just prior to the survey or by transformation of points in a local coordinate system to WGS84
An alternative approach is called the antenna swap method
An antenna is placed at each end of a short base ( 5-10 m ) and observations taken over a short period of time
The antennae are interchanged lock maintained and observations continued
This results in a big change in the relative receiver/satellite geometry and consequently rapid determination of the integers
The antennae are returned to their original position prior to the surveys
It should be realized that the whole survey will be invalidated if a cycle slip occurs Thus reconnaissance of the area is still of vital importance otherwise reinitalization will be necessary
A further help in this matter is to observe to many more satellites than the minimum four required
Traditional kinematic surveying
Assuming the ambiguities have been resolved a master receiver is positioned over a reference point of known coordinates and the roving receiver commences its movement along the route required
As the movement is continuous the observations take place at preset time intervals often less than l s
Lock must be maintained to at least four satellites or re established when lost
In this technique it is the trajectory of the rover that is surveyed and points are surveyed by time rather than position hence linear detail such as roads rivers railways ect can be rapidly surveyed
Antennae can be fitted to fast moving moving vehicles or even bicycles which can be driven along a road or path to obtain a three dimensional profile
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