LRS Micro-g LaCoste FG5, Manual, Page: 104 / 149

Troubleshooting
5
5.3. Gravity Site Selection
5.3.1.GEOLOGIC STABILITY
To achieve best results, a site should be located in a geologically stable
area. Generally, it may be necessary to measure gravity at a particular site for a
number of different reasons, and geologic stability cannot be considered.
However, when selecting a primary base station, geological stability is important
in minimizing long term variations in gravity resulting from groundwater
changes, and subsidence or rebound of the earth’s crust.
5.3.2.SITE STABILITY
It is always best to select a site in the lowest level of a building to reduce
vibrations as much as possible. A basement with a thick concrete floor is usually
best. Avoid floors with composition materials, if possible, and set up the
instrument on a solid tile or concrete floor.
5.3.3.ENVIRONMENTAL NOISE
Heavy heating or cooling equipment, as well as bipedal or vehicular traffic, can
cause vibrations which tend to increase the drop-to-drop scatter of the
observations. This can usually be seen as a large, systematic change in the drop-
to-drop scatter between day and night observations. A remote, environmentally
quiet site usually minimizes these changes.
5.3.4.TEMPERATURE STABILITY
Although the FG5 will operate properly over a wide temperature range, it is
important to have a site with good temperature stability to minimize possible
problems with temperature sensitive components (e.g. laser and Superspring).
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