Chapter 1 Introduction - Thales Z-Max Operation And Application Manual

Introduction
Although difficult to believe, it has been over 20 years since precise positioning using
the Global Positioning System (GPS) was first demonstrated. In a relatively short
time, this capability was put to commercial use with the introduction of the
Macrometer V-1000 GPS receiver. Although the Macrometer was unwieldy,
temperamental, and very expensive ($150,000 each), its ability to geodetically
position points at an accuracy of 1-2 parts-per-million of point separation (1mm per 1
kilometer), without the benefit of line-of-sight between the points, was a tremendous
asset. This was the birth of surveying with GPS.
From its beginning in the early 1980s to the mid 1990s, GPS surveying went through
a tremendous evolution as equipment became much more affordable, reliable, and
manageable in size and weight. But through this entire period, two important
characteristics remained the same; accuracy and the surveying method used to
achieve this accuracy. The method was post-process GPS surveying.
With post-process GPS surveying, data is collected in the field and later downloaded
and processed on a computer to produce the final results, i.e. positions of all points
surveyed. This method can be equated to using a conventional theodolite and an
EDM to collect a sequence of angles and distances between points, later computing
the coordinates of the surveyed points.
Until the mid-1990s, post-processing was the only method available to determine
survey-grade positions using GPS. A new method was then introduced called Real-
Time Kinematic (RTK). With the RTK method, point positions are determined
immediately during data collection. This method can be equated to using a total
station to collect a sequence of angles and distances between points, with the total
station computing the coordinates of these points as the data is collected.
RTK GPS surveying has a number of advantages. The results of your survey are
known immediately. Also, with the ability to determine your position in real-time comes
the ability to stakeout. But balancing the RTK advantages are some significant
disadvantages. RTK-enabled GPS systems are more expensive, in some cases
considerably so. RTK systems are somewhat more complex, requiring management
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