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I.8
Horizontal Alignment
I.9
Initialisation
1048
GNSS survey-
Characteristic
ing technique
Use
Accuracy
Working speed
Refer to standard surveying literature for more details on GNSS surveying tech-
niques.
H
The horizontal alignment defines the road axis of a project. Horizontal align-
ments are comprised of the elements:
•
straights (tangents)
curves (arcs)
•
spirals (clothoid or cubic parabola)
•
•
bloss curves (element type used for railway track design)
Each element involved is defined by individual horizontal design elements such
as chainage, Easting, Northing, radius and parameter A.
I
For cm positioning with GNSS, the ambiguities must be fixed. The process of
fixing ambiguities is called initialisation. In order to carry out an initialisation,
the real-time rover settings must allow for phase fixed solutions. A minimum of
five satellites on L1 and L2 is required.
The rover instrument is moved from the beginning of the GNSS operation on,
recording data. The trajectory of the moving rover is recorded. Ambiguities are
Description
Rover equipment is set up on a pole
•
and moves from one unknown point
to another.
A data link, for example a radio or
•
digital cellular phone, transmits sat-
ellite data from the base to the
rover.
Data coming from the base and
•
GNSS signals received on the rover
are processed together on the rover
as the survey is carried out in real
time.
Ambiguities are solved, coordinates
•
of the surveyed points are calcula-
ted and displayed.
apps as on conventional instru-
•
ments like stakeout or COGO can be
performed.
Post-processing is optional.
•
For surveying detail with many points in
one area.
High for baselines up to 30 km.
Efficient as the results are generated in
the field.
Glossary
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