Hi,

I just ran into another web article on pier construction and sand fill.
This is a Gov. Of Canada design for a remote steel pier - a "GPS Monument" to
hold a GPS in a stable position to measure ground shift.

http://gsc.nrcan.gc.ca/geodyn/wcda/gpsmon_e.php

Notice they pour in "fine grained dry sand" into the pier for thermal
stability. I guess they don't want the GPS unit shifting up or down, or
perhaps sideways, as the pier stretches or shrinks. I suppose this should also
be a consideration for telescope piers as well.

Joe