Sect_5.5.5

5.5.5 Modern GPS Surveying: Field Procedures

KINEMATIC GPS SURVEYING TECHNIQUES

Centimetre positioning accuracy of moving antenna ...

This is a generalisation of the "stop & go" technique. Instead of coordinating stationary points and disregarding the trajectory of the roving antenna as it moves from site to site, the intention of "kinematic" surveying is to determine the position of the antenna only while it is in motion (see Figure below). In many other respects the technique is similar to "stop & go". That is, the ambiguities must be resolved before starting the survey, and the ambiguities must be reinitialised during the survey when a cycle slip occurs. However, for many applications, such as the positioning of an aircraft (for example, for photogrammetric applications) or a ship (for example, a dredging operation), it is impractical to reinitialise the ambiguities if the "roving" antenna has to return to a stationary control point. Hence much R&D effort has been invested in initially determining (and redetermining after a cycle slip) the ambiguities "on-the-fly". Today the "kinematic" GPS surveying technique is undergoing tremendous improvement and "on-the-fly" ambiguity resolution is a routine procedure (though not yet by any means an entirely foolproof one!), making kinematic surveying techniques ideal for road centreline surveys, hydrographic surveys, airborne applications, etc.

The "kinematic" GPS surveying technique.

There are a number of trends in "kinematic" surveying that are worth noting:

There is a blurring of the distinction between "kinematic GPS surveying" and "kinematic GPS navigation". The former is carrier phase based (actually "carrier-range" data), whereas the latter has usually been taken to refer to pseudo-range based positioning. However, nowadays more navigation instruments are using "carrier phase smoothed pseudo-ranges" (section 6.4.11). However, it is still valid to distinguish these techniques as "decimetre accuracy positioning" on the one hand, and "submetre accuracy positioning" on the other hand.
There is trend to using a combination of both phase and pseudo-range data within the positioning algorithm itself, precise C/A code ranges as well as P code pseudo-ranges.
There is an increasing sophistication of the algorithms, for example, incorporating Kalman filters.
There are techniques based on single frequency data, as well as those top-of-the-line procedures requiring dual-frequency data.
"On-the-fly" ambiguity resolution techniques will probably all other "kinematic" techniques (and possibly the "rapid static" and "reoccupation" techniques as well).
Real-time operation ("real-time kinematic" -- RTK) is increasingly popular as it offers considerable advantages in that the results are available immediately, in the field, but it is still a challenge and operates under a number of significant constraints.

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