14
www.javad.com
Collecting data
See the remaining sections in this chapter for more
information on collecting data.
•
Turn on the receiver.
•
Once the receiver has locked on to eight or more
satellites the STAT light will green.
•
The process of locking on to satellites normal-
ly takes less than one minute. In a new area, under
heavy tree canopy, or after resetting the receiver, it
may take several minutes.
•
To begin collecting data, press and hold the FN
button (for more than one second and less than five
seconds).
•
Release the FN button when the REC (recording)
LED turns green. This indicates that a file has opened
and data collection has started. The REC LED blinks
each time data is saved to the internal memory.
• When finished, press and hold the FN button until
the REC LED light goes out.
To turn off the receiver, press and hold the power key
until all lights go out, then release.
Static Surveying for Base Stations
Static surveying is the classic survey method, well
suited for all kinds of baselines (short, medium, long).
At least two receiver antennas, plumbed over survey
marks, simultaneously collect raw data at each end of
a baseline during a certain period of time. These two
receivers track four or more common satellites, have
a common data logging rate (5–30 seconds), and the
same elevation mask angles. The length of the obser-
vation sessions can vary from a few minutes to several
hours. The optimal observation session length depends
on the surveyor’s experience as well as the following
factors:
•
The length of the baseline measured
•
The number of satellites in view
•
The satellite geometry (DOP)
•
The antenna’s location
•
The ionospheric activity level
•
The types of receivers used
•
The accuracy requirements
•
The necessity of resolving carrier phase ambigu-
ities
Generally, single-frequency receivers are used for
baselines whose lengths do not exceed 15 kilometers
(9.32 miles). For baselines of 15 kilometers or greater,
use dual-frequency receivers.
Dual-frequency receivers have two major benefits.
First, dual frequency receivers can estimate and remove
almost all ionospheric effect from the code and carrier
phase measurements, providing much greater accuracy
than single-frequency receivers over long baselines or
during ionospheric storms. Secondly, dual-frequency
receivers need far less observation time to reach the de-
sired accuracy requirement.
After the survey completes, data the receivers col-
lect can be downloaded onto a computer and processed
using post-processing software (for example, JAVAD
GNSS Justin).
Kinematic (Stop & Go) Surveying for Rover
Stations
In a kinematic, stop and go survey, the stationary re-
ceiver (Base station) is set up at a known point such as
a survey monument, or an unknown point. The receiver
continually tracks satellites and logs raw data into its
memory. The Rover receiver is set up at an unknown
point and collects data in static mode for 2 to 10 min-
utes. When finished, assign the Rover to kinematic sta
-
tus and move to the next survey point. At this point, and
each subsequent point, the receiver is changed to static
mode to collect data. So, while moving, the Rover is in
kinematic mode, and while collecting data, the Rover is
in static mode.
•
Set up the Rover at an unknown point and press
power. Allow the Rover to collect static data for two
to ten minutes. The REC LED will be yellow.
•
Check the SAT light for satellites tracked.
• When finished, press the FN button for less than 1
second to assign the Rover to kinematic.
•
Move the Rover to the next location (survey point),
and press the FN button for less than a second to col-
lect the data in static mode for two to ten minutes.
• Repeat steps five and six until all points have been
surveyed. The occupation time for the points de-
pends on the same factors as for the static survey
method.
• When finished, press the FN button for one to five
seconds to stop logging data. Turn off the Rover if
needed. This method of GNSS survey allows the
operator to reduce the point occupation time, thus
permitting field crews to survey many more points
compared to the other methods available.
Содержание DELTA-3
Страница 21: ...www javad com 21 ...
