Static Surveys - Thales Z-Max Operation And Application Manual

Static Surveys

Prior to leaving the office to perform a GPS survey, check the following items:
• Check through the Z-Max equipment and the modules to ensure all
components are present to successfully perform the survey. Going
through a written checklist before fieldwork is a good practice.
• Check to ensure that the Power module and any external batteries to be
used are charged. Z-Max Power Modules need to be calibrated
periodically to ensure precise agreement between the battery capacity
indicators and the actual battery capacity.
• Use the Mission Planning module from GNSS Studio software to check the
satellite availability for the time period when data are collected. Ensure
that the number of satellites, their geometry and the observation time is
sufficient to support the desired results.
The number of satellites needed for a given result will vary based on
factors such as baseline length and occupation time. Typically for Static
surveying, continuous lock must be maintained with 4 or more satellites
during 10-60 minute blocks of time. For Kinematic surveying, continuous
lock must be maintained with 5 or more satellites during blocks of at least
15 min. The longer the baseline length, the longer occupation time that is
required for survey quality results.
Satellite geometry is measured using a calculated value called Dilution of
Precision (DOP). A number of different DOP metrics exist, the most useful
of which is Position Dilution of Precision (PDOP). The Mission Planning
software module will give PDOP values for the time periods in which data
is intended to be collected. Avoid collecting data during periods where
PDOP values are larger than 4 (the lower the number the better). Refer to
the documentation accompanying the GNSS Studio software for more
details on PDOP and how to use the Mission Planning software module to
determine when data should be and should not be collected.
With the previous checklist completed, field data collection can begin.
When collecting data using the Static method, each Z-Max receiver will follow
precisely the same steps in equipment setup and survey execution. These steps are
presented below.
Survey Preparation and Execution 125