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Precise Surveying - Field Applications & Concepts
Choosing a Location for the Base
First Criterion:
GNSS Reception
Conditions
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In distance mode, a new marker is created every x meters.
In time mode, a new marker is created every x seconds,
where "x" is the log interval.
While you are walking along the trajectory, the rover
inserts new markers into the logged raw data file
according to the chosen log interval. Each marker is
named as a point. The name includes a numeral suffix
that is automatically incremented for each new logged
marker. You must take care however to use a log interval
that is compatible with the raw data recording rate:
In time mode:
log interval (s) >2 x raw data recording rate (s)
In distance mode:
log interval (m) > 2 x walking speed (m/s) x raw data recording rate (s)
4. Number of trajectories in a single file. Some receivers,
such as the ProMark 500, allow you to log a single
trajectory into a raw data file. Some others, like the
ProMark3, allow you to enter several start/stop markers in
the same file meaning that several trajectories can be
logged in the same file.
The location of the base is fundamental for the success of
your survey. Whether you are in post-processing or real-time
mode and your receivers are single- or dual-frequency,
remember the rover position will always be computed relative
to the base position. Any inaccuracy in the base position will
inevitably be transferred to the position computed by the
rover.
This section discusses the two basic criteria to be taken into
account when installing a base:
1. GNSS reception conditions
2. Base position known or unknown?
When a base radio is used, there is a third criterion to be
taken into account in the choice of the base location, which
is the ability to install the radio antenna as high as possible,
with a minimum of obstructions to the working area, so that
the radio range can be as good as expected.
Make sure the base is sited in a clear area giving the best
possible view of the sky.
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